import "@std/mem"
import "@std/testing"

import "@source/diagnostics"
import "@source/strpool"
import "@source/lexer"
import "@source/parser"
import "@source/ast"
sema :: import "@source/sema"

@hide:file
expect_kind proc(result @Result, id ast.NodeId, expected TypeKind) void ! testing.Error {
    try testing.expect_equal(expected, type_of(result, id).kind)
    try testing.expect_equal(diagnostics.no_diagnostic, type_of(result, id).diagnostic)
}

@hide:file
expect_error proc(
    result @Result,
    diagnostic_store @diagnostics.Store,
    id ast.NodeId,
    code diagnostics.Code,
    span ast.Span,
) diagnostics.DiagnosticId ! testing.Error {
    actual :: type_of(result, id)
    try testing.expect_equal(TypeKind.invalid, actual.kind)
    if (diagnostics.get(diagnostic_store, actual.diagnostic)) |diagnostic| {
        try testing.expect_equal(code, diagnostic.code)
        try testing.expect_equal(span.start, diagnostic.span.start)
        try testing.expect_equal(span.end, diagnostic.span.end)
    } else {
        return .expectation_failed
    }
    return actual.diagnostic
}

@hide:file
expect_fallthrough proc(
    result @Result,
    diagnostic_store @diagnostics.Store,
    function ast.NodeId,
    span ast.Span,
) diagnostics.DiagnosticId ! testing.Error {
    if (fallthrough_diagnostic(result, function)) |id| {
        if (diagnostics.get(diagnostic_store, id)) |diagnostic| {
            try testing.expect_equal(diagnostics.Code.missing_return, diagnostic.code)
            try testing.expect_equal(span.start, diagnostic.span.start)
            try testing.expect_equal(span.end, diagnostic.span.end)
            return id
        }
    }
    return .expectation_failed
}

@hide:file
code_count proc(diagnostic_store @diagnostics.Store, code diagnostics.Code) usize {
    count := usize(0)
    for 0..diagnostics.count(diagnostic_store) |index| {
        if (diagnostics.get(diagnostic_store, diagnostics.DiagnosticId(index))) |diagnostic| {
            if (diagnostic.code == code) count += 1
        }
    }
    return count
}

propagates_numeric_context_before_defaulting_forward_and_mutable_aliases test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `forward float :: -forwarded * 2 + seed
        `forwarded :: seed
        `seed := 3
        `backward :: 4
        `demand float :: backward
        `quotient :: -3 / 2 + 1
        `mixed :: 3 / 2
        `plain :: -3 + 2 * 4
        `fraction :: 1.5
        `text :: "honey"
        `fixed int :: 7
        `anchored :: fixed + 2
        `nested float :: quotient / (forwarded + 1)
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    try testing.expect_equal(0, diagnostics.count(&diagnostic_store))
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    expected [13]TypeKind :: [
        .float, .float, .float, .float, .float, .float, .float,
        .int, .float, .string, .int, .int, .float,
    ]
    for expected |kind, index| {
        declaration :: ast.package_decl(&tree, index)
        view :: ast.statement_decl(&tree, declaration)
        try expect_kind(&result, declaration, kind)
        try expect_kind(&result, view.initializer, kind)
        if (view.type) |annotation| try expect_kind(&result, annotation, kind)
    }
    forward :: ast.binary_expr(&tree, ast.statement_decl(&tree, ast.package_decl(&tree, 0)).initializer)
    multiply :: ast.binary_expr(&tree, forward.left)
    negate :: ast.unary_expr(&tree, multiply.left)
    numeric_nodes [6]ast.NodeId :: [
        forward.left, forward.right, multiply.left, multiply.right, negate.operand,
        ast.statement_decl(&tree, ast.package_decl(&tree, 2)).initializer,
    ]
    for (numeric_nodes) |id| try expect_kind(&result, id, .float)
    quotient :: ast.binary_expr(&tree, ast.statement_decl(&tree, ast.package_decl(&tree, 5)).initializer)
    mixed :: ast.binary_expr(&tree, ast.statement_decl(&tree, ast.package_decl(&tree, 6)).initializer)
    division_operands [4]ast.NodeId :: [quotient.left, quotient.right, mixed.left, mixed.right]
    for (division_operands) |id| try expect_kind(&result, id, .float)
    try testing.expect_equal(0, diagnostics.count(&diagnostic_store))
}

rejects_fixed_family_conversion_integer_division_and_conflicting_demands test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `fixed int :: 1
        `real float :: 2
        `widen float :: fixed
        `narrow int :: 1.5
        `cross :: fixed + real
        `division :: fixed / 2
        `negated :: -"x"
        `strings :: "a" + "b"
        `first_int int :: conflict_a
        `first_float float :: conflict_a
        `conflict_a := 5
        `reverse_float float :: conflict_b
        `reverse_int int :: conflict_b
        `conflict_b :: 6
        `good :: 9
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    try testing.expect_equal(0, diagnostics.count(&diagnostic_store))
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    try expect_kind(&result, ast.package_decl(&tree, 0), .int)
    try expect_kind(&result, ast.package_decl(&tree, 1), .float)
    codes [6]diagnostics.Code :: [
        .type_mismatch, .type_mismatch, .invalid_operand,
        .integer_division, .invalid_operand, .invalid_operand,
    ]
    for codes |code, index| {
        declaration :: ast.package_decl(&tree, index + 2)
        expression :: ast.statement_decl(&tree, declaration).initializer
        diagnostic :: try expect_error(&result, &diagnostic_store, expression, code, ast.node_span(&tree, expression))
        try testing.expect_equal(TypeKind.invalid, type_of(&result, declaration).kind)
        try testing.expect_equal(diagnostic, type_of(&result, declaration).diagnostic)
    }
    conflicts [2]ast.NodeId :: [ast.package_decl(&tree, 10), ast.package_decl(&tree, 13)]
    for conflicts |declaration| {
        try testing.expect_equal(TypeKind.invalid, type_of(&result, declaration).kind)
        diagnostic :: type_of(&result, declaration).diagnostic
        if (diagnostics.get(&diagnostic_store, diagnostic)) |error| try testing.expect_equal(diagnostics.Code.type_mismatch, error.code)
        else return .expectation_failed
        try testing.expect_equal(diagnostic, type_of(&result, ast.statement_decl(&tree, declaration).initializer).diagnostic)
    }
    conflict_uses [4]usize :: [8, 9, 11, 12]
    for conflict_uses |index| {
        declaration :: ast.package_decl(&tree, index)
        target :: if (index < 11) conflicts[0] else conflicts[1]
        try testing.expect_equal(TypeKind.invalid, type_of(&result, declaration).kind)
        try testing.expect_equal(type_of(&result, target).diagnostic, type_of(&result, declaration).diagnostic)
    }
    try expect_kind(&result, ast.package_decl(&tree, 14), .int)
    try testing.expect_equal(0, code_count(&diagnostic_store, .cannot_infer_type))
}

checks_forward_alias_calls_grouped_parameters_and_mutual_recursion test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `forwarded :: alpha
        `alpha proc(a, b int) void {
        `    (forwarded)(a, b)
        `    beta(a + b, seed)
        `}
        `beta proc(total int, amount float) void {
        `    alpha(total, 2)
        `}
        `seed := 3
        `main proc() void {
        `    beta(1, 2)
        `    (forwarded)(3, 4)
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    alias_decl :: ast.package_decl(&tree, 0)
    alpha :: ast.package_decl(&tree, 1)
    beta :: ast.package_decl(&tree, 2)
    seed :: ast.package_decl(&tree, 3)
    main_function :: ast.package_decl(&tree, 4)
    functions [3]ast.NodeId :: [alpha, beta, main_function]
    for functions |function| {
        try expect_kind(&result, function, .function)
        try testing.expect_equal(function, type_of(&result, function).function)
        try expect_kind(&result, ast.function_decl(&tree, function).return_type, .void)
    }
    try expect_kind(&result, alias_decl, .function)
    try testing.expect_equal(alpha, type_of(&result, alias_decl).function)
    try testing.expect_equal(alpha, type_of(&result, ast.statement_decl(&tree, alias_decl).initializer).function)
    alpha_body :: ast.function_decl(&tree, alpha).body
    beta_body :: ast.function_decl(&tree, beta).body
    main_body :: ast.function_decl(&tree, main_function).body
    calls [5]ast.NodeId :: [
        ast.statement_expr(&tree, ast.block_statement(&tree, alpha_body, 0)),
        ast.statement_expr(&tree, ast.block_statement(&tree, alpha_body, 1)),
        ast.statement_expr(&tree, ast.block_statement(&tree, beta_body, 0)),
        ast.statement_expr(&tree, ast.block_statement(&tree, main_body, 0)),
        ast.statement_expr(&tree, ast.block_statement(&tree, main_body, 1)),
    ]
    callees [5]ast.NodeId :: [alpha, beta, alpha, beta, alpha]
    for calls |call, index| {
        try expect_kind(&result, call, .void)
        callee :: ast.call_expr(&tree, call).callee
        try expect_kind(&result, callee, .function)
        try testing.expect_equal(callees[index], type_of(&result, callee).function)
        try expect_kind(&result, ast.call_arg(&tree, call, 0), .int)
        expected TypeKind :: if (index == 1 or index == 3) .float else .int
        try expect_kind(&result, ast.call_arg(&tree, call, 1), expected)
    }
    try expect_kind(&result, seed, .float)
    try expect_kind(&result, ast.statement_decl(&tree, seed).initializer, .float)
    a :: ast.function_param(&tree, alpha, 0)
    b :: ast.function_param(&tree, alpha, 1)
    try testing.expect_equal(ast.param(&tree, a).type, ast.param(&tree, b).type)
    try expect_kind(&result, a, .int)
    try expect_kind(&result, b, .int)
    try expect_kind(&result, ast.param(&tree, a).type, .int)
    try expect_kind(&result, ast.function_param(&tree, beta, 1), .float)
    try testing.expect_equal(0, diagnostics.count(&diagnostic_store))
}

separates_type_annotations_from_values_and_restricts_void_storage test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `value :: 1
        `bad value :: -"x"
        `builtin :: int
        `grouped proc(a, b value) value {}
        `void_params proc(a, b void) void {}
        `storage void :: 1
        `noop proc() void {}
        `sink proc(p int) void {}
        `holder :: noop()
        `operand :: noop() + 1
        `main proc() void {
        `    noop()
        `    sink(noop())
        `}
        `good string :: "ok"
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    try testing.expect_equal(0, diagnostics.count(&diagnostic_store))
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    bad :: ast.statement_decl(&tree, ast.package_decl(&tree, 1))
    if (bad.type) |annotation| _ = try expect_error(&result, &diagnostic_store, annotation, .expected_type, ast.node_span(&tree, annotation))
    else return .expectation_failed
    _ = try expect_error(&result, &diagnostic_store, bad.initializer, .invalid_operand, ast.node_span(&tree, bad.initializer))
    builtin :: ast.statement_decl(&tree, ast.package_decl(&tree, 2)).initializer
    _ = try expect_error(&result, &diagnostic_store, builtin, .type_not_value, ast.node_span(&tree, builtin))
    grouped :: ast.package_decl(&tree, 3)
    a :: ast.function_param(&tree, grouped, 0)
    b :: ast.function_param(&tree, grouped, 1)
    shared_type :: ast.param(&tree, a).type
    try testing.expect_equal(shared_type, ast.param(&tree, b).type)
    shared_error :: try expect_error(&result, &diagnostic_store, shared_type, .expected_type, ast.node_span(&tree, shared_type))
    try testing.expect_equal(shared_error, type_of(&result, a).diagnostic)
    try testing.expect_equal(shared_error, type_of(&result, b).diagnostic)
    return_type :: ast.function_decl(&tree, grouped).return_type
    _ = try expect_error(&result, &diagnostic_store, return_type, .expected_type, ast.node_span(&tree, return_type))
    void_function :: ast.package_decl(&tree, 4)
    void_a :: ast.function_param(&tree, void_function, 0)
    void_b :: ast.function_param(&tree, void_function, 1)
    void_annotation :: ast.param(&tree, void_a).type
    void_error :: try expect_error(&result, &diagnostic_store, void_annotation, .invalid_void_type, ast.node_span(&tree, void_annotation))
    try testing.expect_equal(void_annotation, ast.param(&tree, void_b).type)
    try testing.expect_equal(void_error, type_of(&result, void_a).diagnostic)
    try testing.expect_equal(void_error, type_of(&result, void_b).diagnostic)
    try expect_kind(&result, ast.function_decl(&tree, void_function).return_type, .void)
    storage :: ast.statement_decl(&tree, ast.package_decl(&tree, 5))
    if (storage.type) |annotation| _ = try expect_error(&result, &diagnostic_store, annotation, .invalid_void_type, ast.node_span(&tree, annotation))
    else return .expectation_failed
    holder :: ast.statement_decl(&tree, ast.package_decl(&tree, 8)).initializer
    _ = try expect_error(&result, &diagnostic_store, holder, .type_mismatch, ast.node_span(&tree, holder))
    operand :: ast.statement_decl(&tree, ast.package_decl(&tree, 9)).initializer
    _ = try expect_error(&result, &diagnostic_store, operand, .invalid_operand, ast.node_span(&tree, operand))
    main_body :: ast.function_decl(&tree, ast.package_decl(&tree, 10)).body
    noop_call :: ast.statement_expr(&tree, ast.block_statement(&tree, main_body, 0))
    try expect_kind(&result, noop_call, .void)
    bad_call :: ast.statement_expr(&tree, ast.block_statement(&tree, main_body, 1))
    argument :: ast.call_arg(&tree, bad_call, 0)
    argument_error :: try expect_error(&result, &diagnostic_store, argument, .type_mismatch, ast.node_span(&tree, argument))
    try testing.expect_equal(argument_error, type_of(&result, bad_call).diagnostic)
    rejected [5]usize :: [1, 2, 5, 8, 9]
    for rejected |index| {
        try testing.expect_equal(TypeKind.invalid, type_of(&result, ast.package_decl(&tree, index)).kind)
    }
    try expect_kind(&result, storage.initializer, .int)
    try expect_kind(&result, ast.package_decl(&tree, 0), .int)
    try expect_kind(&result, ast.package_decl(&tree, 11), .string)
    try testing.expect_equal(3, code_count(&diagnostic_store, .expected_type))
    try testing.expect_equal(2, code_count(&diagnostic_store, .invalid_void_type))
    try testing.expect_equal(1, code_count(&diagnostic_store, .type_not_value))
    try testing.expect_equal(2, code_count(&diagnostic_store, .type_mismatch))
    try testing.expect_equal(2, code_count(&diagnostic_store, .invalid_operand))
    try testing.expect_equal(10, diagnostics.count(&diagnostic_store))
}

reports_nonvoid_fallthrough_without_poisoning_signatures_and_checks_unused_bodies test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `answer :: forwarded()
        `forwarded :: make
        `make proc() int {}
        `unused proc() float {}
        `broken proc() void {
        `    -"x"
        `}
        `main proc() void {
        `    make()
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    answer :: ast.package_decl(&tree, 0)
    alias_decl :: ast.package_decl(&tree, 1)
    make :: ast.package_decl(&tree, 2)
    unused :: ast.package_decl(&tree, 3)
    try expect_kind(&result, answer, .int)
    try expect_kind(&result, ast.statement_decl(&tree, answer).initializer, .int)
    try expect_kind(&result, alias_decl, .function)
    try testing.expect_equal(make, type_of(&result, alias_decl).function)
    functions [2]ast.NodeId :: [make, unused]
    returns [2]TypeKind :: [.int, .float]
    for functions |function, index| {
        view :: ast.function_decl(&tree, function)
        try expect_kind(&result, function, .function)
        try testing.expect_equal(function, type_of(&result, function).function)
        try expect_kind(&result, view.return_type, returns[index])
        _ = try expect_fallthrough(&result, &diagnostic_store, function, ast.node_span(&tree, view.body))
    }
    broken :: ast.package_decl(&tree, 4)
    try expect_kind(&result, broken, .function)
    try testing.expect_equal(null, fallthrough_diagnostic(&result, broken))
    broken_body :: ast.function_decl(&tree, broken).body
    bad_operand :: ast.statement_expr(&tree, ast.block_statement(&tree, broken_body, 0))
    _ = try expect_error(&result, &diagnostic_store, bad_operand, .invalid_operand, ast.node_span(&tree, bad_operand))
    main_body :: ast.function_decl(&tree, ast.package_decl(&tree, 5)).body
    try testing.expect_equal(null, fallthrough_diagnostic(&result, ast.package_decl(&tree, 5)))
    call :: ast.statement_expr(&tree, ast.block_statement(&tree, main_body, 0))
    try expect_kind(&result, call, .int)
    try testing.expect_equal(2, code_count(&diagnostic_store, .missing_return))
    try testing.expect_equal(3, diagnostics.count(&diagnostic_store))
}

checks_arguments_even_for_wrong_arity_noncallable_and_chained_callees test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `sink proc(a int, b float) void {}
        `noop proc() void {}
        `fixed int :: 1
        `main proc() void {
        `    sink(1, 2, -"extra")
        `    sink()
        `    fixed(-"arg")
        `    sink(1, "wrong")
        `    sink(1, fixed)
        `    noop()()
        `    sink(2, 3)
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    body :: ast.function_decl(&tree, ast.package_decl(&tree, 3)).body
    for usize(0)..usize(2) |index| {
        call :: ast.statement_expr(&tree, ast.block_statement(&tree, body, index))
        _ = try expect_error(&result, &diagnostic_store, call, .argument_count_mismatch, ast.node_span(&tree, call))
    }
    long_call :: ast.statement_expr(&tree, ast.block_statement(&tree, body, 0))
    extra :: ast.call_arg(&tree, long_call, 2)
    _ = try expect_error(&result, &diagnostic_store, extra, .invalid_operand, ast.node_span(&tree, extra))
    try expect_kind(&result, ast.call_arg(&tree, long_call, 0), .int)
    try expect_kind(&result, ast.call_arg(&tree, long_call, 1), .float)
    noncall :: ast.statement_expr(&tree, ast.block_statement(&tree, body, 2))
    noncall_callee :: ast.call_expr(&tree, noncall).callee
    _ = try expect_error(&result, &diagnostic_store, noncall, .not_callable, ast.node_span(&tree, noncall_callee))
    bad_argument :: ast.call_arg(&tree, noncall, 0)
    _ = try expect_error(&result, &diagnostic_store, bad_argument, .invalid_operand, ast.node_span(&tree, bad_argument))
    for usize(3)..usize(5) |index| {
        call :: ast.statement_expr(&tree, ast.block_statement(&tree, body, index))
        argument :: ast.call_arg(&tree, call, 1)
        diagnostic :: try expect_error(&result, &diagnostic_store, argument, .type_mismatch, ast.node_span(&tree, argument))
        try testing.expect_equal(diagnostic, type_of(&result, call).diagnostic)
    }
    chained :: ast.statement_expr(&tree, ast.block_statement(&tree, body, 5))
    inner :: ast.call_expr(&tree, chained).callee
    try expect_kind(&result, inner, .void)
    _ = try expect_error(&result, &diagnostic_store, chained, .not_callable, ast.node_span(&tree, inner))
    good_call :: ast.statement_expr(&tree, ast.block_statement(&tree, body, 6))
    try expect_kind(&result, good_call, .void)
    try expect_kind(&result, ast.call_arg(&tree, good_call, 1), .float)
    try expect_kind(&result, ast.package_decl(&tree, 2), .int)
    try testing.expect_equal(2, code_count(&diagnostic_store, .argument_count_mismatch))
    try testing.expect_equal(2, code_count(&diagnostic_store, .not_callable))
    try testing.expect_equal(2, code_count(&diagnostic_store, .invalid_operand))
    try testing.expect_equal(2, code_count(&diagnostic_store, .type_mismatch))
    try testing.expect_equal(8, diagnostics.count(&diagnostic_store))
}

terminates_unanchored_cycles_and_keeps_grounded_cycles_typed test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `a :: b
        `b :: a
        `dependent :: a
        `self :: self
        `anchored float :: partner
        `partner :: anchored
        `fixed int :: fixed
        `good :: 2
        `numeric :: numeric + 1
        `demand float :: contextual_a
        `contextual_a :: contextual_b
        `contextual_b :: contextual_a
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    try testing.expect_equal(0, diagnostics.count(&diagnostic_store))
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    a :: ast.package_decl(&tree, 0)
    b :: ast.package_decl(&tree, 1)
    dependent :: ast.package_decl(&tree, 2)
    shared :: type_of(&result, a).diagnostic
    cycle [3]ast.NodeId :: [a, b, dependent]
    for cycle |declaration| {
        try testing.expect_equal(TypeKind.invalid, type_of(&result, declaration).kind)
        try testing.expect_equal(shared, type_of(&result, declaration).diagnostic)
        expression :: ast.statement_decl(&tree, declaration).initializer
        try testing.expect_equal(TypeKind.invalid, type_of(&result, expression).kind)
        try testing.expect_equal(shared, type_of(&result, expression).diagnostic)
    }
    if (diagnostics.get(&diagnostic_store, shared)) |diagnostic| {
        try testing.expect_equal(diagnostics.Code.cannot_infer_type, diagnostic.code)
        a_name :: ast.statement_decl(&tree, a).name
        b_name :: ast.statement_decl(&tree, b).name
        try testing.expect(
            (diagnostic.span.start == a_name.start and diagnostic.span.end == a_name.end)
            or (diagnostic.span.start == b_name.start and diagnostic.span.end == b_name.end),
        )
    } else {
        return .expectation_failed
    }
    self :: ast.package_decl(&tree, 3)
    self_error :: try expect_error(&result, &diagnostic_store, self, .cannot_infer_type, ast.statement_decl(&tree, self).name)
    try testing.expect(self_error != shared)
    try testing.expect_equal(self_error, type_of(&result, ast.statement_decl(&tree, self).initializer).diagnostic)
    for usize(4)..usize(6) |index| {
        declaration :: ast.package_decl(&tree, index)
        try expect_kind(&result, declaration, .float)
        try expect_kind(&result, ast.statement_decl(&tree, declaration).initializer, .float)
    }
    try expect_kind(&result, ast.package_decl(&tree, 6), .int)
    try expect_kind(&result, ast.statement_decl(&tree, ast.package_decl(&tree, 6)).initializer, .int)
    try expect_kind(&result, ast.package_decl(&tree, 7), .int)
    numeric :: ast.package_decl(&tree, 8)
    try expect_kind(&result, numeric, .int)
    try expect_kind(&result, ast.statement_decl(&tree, numeric).initializer, .int)
    for usize(9)..usize(12) |index| {
        declaration :: ast.package_decl(&tree, index)
        try expect_kind(&result, declaration, .float)
        try expect_kind(&result, ast.statement_decl(&tree, declaration).initializer, .float)
    }
    try testing.expect_equal(2, diagnostics.count(&diagnostic_store))
}

preserves_existing_syntax_name_and_duplicate_ids_while_checking_siblings test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `@ broken
        `main proc(a, b Missing) void {
        `    empty :: ()
        `    bad :: absent + -"sibling"
        `    unknown(-"argument")
        `    valid float :: later
        `    later := 1
        `    discarded(1 2)
        `}
        `same :: 1
        `same :: -"initializer"
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    previous_count :: diagnostics.count(&diagnostic_store)
    function :: ast.package_decl(&tree, 1)
    body :: ast.function_decl(&tree, function).body
    invalid_decl :: ast.package_decl(&tree, 0)
    empty_decl :: ast.block_statement(&tree, body, 0)
    empty :: ast.statement_decl(&tree, empty_decl).initializer
    invalid_statement :: ast.block_statement(&tree, body, 5)
    bad_decl :: ast.block_statement(&tree, body, 1)
    bad_expr :: ast.statement_decl(&tree, bad_decl).initializer
    bad :: ast.binary_expr(&tree, bad_expr)
    unknown_call :: ast.statement_expr(&tree, ast.block_statement(&tree, body, 2))
    unknown_callee :: ast.call_expr(&tree, unknown_call).callee
    duplicate :: ast.package_decl(&tree, 3)
    a :: ast.function_param(&tree, function, 0)
    b :: ast.function_param(&tree, function, 1)
    shared_type :: ast.param(&tree, a).type
    try testing.expect_equal(shared_type, ast.param(&tree, b).type)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    syntax_nodes [3]ast.NodeId :: [invalid_decl, empty, invalid_statement]
    for syntax_nodes |id| {
        try testing.expect_equal(TypeKind.invalid, type_of(&result, id).kind)
        try testing.expect_equal(ast.invalid(&tree, id).diagnostic, type_of(&result, id).diagnostic)
    }
    try testing.expect_equal(type_of(&result, empty).diagnostic, type_of(&result, empty_decl).diagnostic)
    resolved_invalid [4]ast.NodeId :: [shared_type, bad.left, unknown_callee, duplicate]
    for resolved_invalid |id| {
        try testing.expect_equal(sema.BindingKind.invalid, sema.binding(&resolution, id).kind)
        try testing.expect_equal(TypeKind.invalid, type_of(&result, id).kind)
        try testing.expect_equal(sema.binding(&resolution, id).data.diagnostic, type_of(&result, id).diagnostic)
    }
    try testing.expect_equal(type_of(&result, shared_type).diagnostic, type_of(&result, a).diagnostic)
    try testing.expect_equal(type_of(&result, shared_type).diagnostic, type_of(&result, b).diagnostic)
    try testing.expect_equal(type_of(&result, bad.left).diagnostic, type_of(&result, bad_expr).diagnostic)
    try testing.expect_equal(type_of(&result, bad.left).diagnostic, type_of(&result, bad_decl).diagnostic)
    try testing.expect_equal(type_of(&result, unknown_callee).diagnostic, type_of(&result, unknown_call).diagnostic)
    _ = try expect_error(&result, &diagnostic_store, bad.right, .invalid_operand, ast.node_span(&tree, bad.right))
    argument :: ast.call_arg(&tree, unknown_call, 0)
    _ = try expect_error(&result, &diagnostic_store, argument, .invalid_operand, ast.node_span(&tree, argument))
    duplicate_initializer :: ast.statement_decl(&tree, duplicate).initializer
    _ = try expect_error(&result, &diagnostic_store, duplicate_initializer, .invalid_operand, ast.node_span(&tree, duplicate_initializer))
    for usize(3)..usize(5) |index| {
        declaration :: ast.block_statement(&tree, body, index)
        try expect_kind(&result, declaration, .float)
        try expect_kind(&result, ast.statement_decl(&tree, declaration).initializer, .float)
    }
    try expect_kind(&result, ast.package_decl(&tree, 2), .int)
    try testing.expect_equal(3, code_count(&diagnostic_store, .unknown_name))
    try testing.expect_equal(1, code_count(&diagnostic_store, .duplicate_name))
    try testing.expect_equal(3, code_count(&diagnostic_store, .invalid_operand))
    try testing.expect_equal(previous_count + 3, diagnostics.count(&diagnostic_store))
}

returns_supply_numeric_context_and_resolve_forward_local_and_parameter_names test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `fraction proc() float {
        `    return -later / 2
        `    later := seed
        `}
        `identity proc(value int) int { return value }
        `wrapper proc() void { return noop() }
        `noop proc() void { return }
        `text proc() string { return "honey" }
        `seed :: 3
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    expected [5]TypeKind :: [.float, .int, .void, .void, .string]
    for (expected) |kind, index| {
        function :: ast.package_decl(&tree, index)
        view :: ast.function_decl(&tree, function)
        try expect_kind(&result, function, .function)
        try expect_kind(&result, view.return_type, kind)
        statement :: ast.block_statement(&tree, view.body, 0)
        try expect_kind(&result, statement, .void)
        if (ast.return_stmt(&tree, statement).value) |value| try expect_kind(&result, value, kind)
    }
    fraction :: ast.function_decl(&tree, ast.package_decl(&tree, 0))
    local :: ast.block_statement(&tree, fraction.body, 1)
    try expect_kind(&result, local, .float)
    try expect_kind(&result, ast.package_decl(&tree, 5), .float)
    if (ast.return_stmt(&tree, ast.block_statement(&tree, fraction.body, 0)).value) |value| {
        division :: ast.binary_expr(&tree, value)
        negate :: ast.unary_expr(&tree, division.left)
        try expect_kind(&result, division.left, .float)
        try expect_kind(&result, division.right, .float)
        try testing.expect_equal(local, sema.binding(&resolution, negate.operand).data.declaration)
    } else {
        return .expectation_failed
    }
    identity :: ast.package_decl(&tree, 1)
    identity_body :: ast.function_decl(&tree, identity).body
    if (ast.return_stmt(&tree, ast.block_statement(&tree, identity_body, 0)).value) |value| try testing.expect_equal(ast.function_param(&tree, identity, 0), sema.binding(&resolution, value).data.declaration)
    else return .expectation_failed
    try testing.expect_equal(0, diagnostics.count(&diagnostic_store))
}

return_errors_preserve_identity_check_unreachable_code_and_suppress_missing_return_cascades test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `bare proc() int { return }
        `wrong proc() int { return "text" }
        `void_value proc() void { return 1 }
        `unknown proc() int { return absent }
        `syntax proc() int { return (1 }
        `after_return proc() int {
        `    return 7
        `    -"bad"
        `}
        `fallthrough proc() int {}
        `recovered proc() int {
        `    return 1 stray
        `    valid :: 2
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    for (usize(0)..usize(3)) |index| {
        function :: ast.package_decl(&tree, index)
        view :: ast.function_decl(&tree, function)
        try expect_kind(&result, function, .function)
        statement :: ast.block_statement(&tree, view.body, 0)
        returned :: ast.return_stmt(&tree, statement)
        span :: if (returned.value) |value| ast.node_span(&tree, value) else returned.span
        diagnostic :: try expect_error(&result, &diagnostic_store, statement, .return_type_mismatch, span)
        if (returned.value) |value| try testing.expect_equal(diagnostic, type_of(&result, value).diagnostic)
    }
    for (usize(3)..usize(5)) |index| {
        view :: ast.function_decl(&tree, ast.package_decl(&tree, index))
        statement :: ast.block_statement(&tree, view.body, 0)
        if (ast.return_stmt(&tree, statement).value) |value| {
            original :: type_of(&result, value).diagnostic
            try testing.expect(original != diagnostics.no_diagnostic)
            try testing.expect_equal(original, type_of(&result, statement).diagnostic)
            try testing.expect_equal(original, type_of(&result, view.body).diagnostic)
        } else {
            return .expectation_failed
        }
    }
    unreachable_body :: ast.function_decl(&tree, ast.package_decl(&tree, 5)).body
    try expect_kind(&result, ast.block_statement(&tree, unreachable_body, 0), .void)
    bad :: ast.statement_expr(&tree, ast.block_statement(&tree, unreachable_body, 1))
    _ = try expect_error(&result, &diagnostic_store, bad, .invalid_operand, ast.node_span(&tree, bad))
    missing :: ast.package_decl(&tree, 6)
    missing_body :: ast.function_decl(&tree, missing).body
    _ = try expect_fallthrough(&result, &diagnostic_store, missing, ast.node_span(&tree, missing_body))
    recovered_body :: ast.function_decl(&tree, ast.package_decl(&tree, 7)).body
    try expect_kind(&result, ast.block_statement(&tree, recovered_body, 1), .int)
    try testing.expect_equal(3, code_count(&diagnostic_store, .return_type_mismatch))
    try testing.expect_equal(1, code_count(&diagnostic_store, .missing_return))
    try testing.expect_equal(1, code_count(&diagnostic_store, .unknown_name))
    try testing.expect_equal(2, code_count(&diagnostic_store, .unexpected_token))
    try testing.expect_equal(8, diagnostics.count(&diagnostic_store))
}

checks_bool_comparisons_recursive_returns_and_nested_numeric_context test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `flag bool :: true
        `same :: flag == false
        `different :: true != flag
        `less :: forwarded < 4.0
        `less_equal :: seed <= 5
        `greater :: 6 > seed
        `greater_equal :: seed >= 1
        `equal :: seed == 3
        `not_equal :: seed != 2
        `forwarded :: seed
        `seed := 3
        `identity proc(value bool) bool { return value }
        `factorial proc(n int) int {
        `    if n <= 1 { return 1 }
        `    return n * factorial(n - 1)
        `}
        `fraction proc(value bool) float {
        `    if value {
        `        before :: later
        `        later := 3
        `        return -before / 2
        `    } else if false {
        `        later :: 4
        `        return later
        `    } else {
        `        return 5
        `    }
        `}
        `main proc() bool { return identity(flag) }
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    for (0..usize(9)) |i| {
        declaration :: ast.package_decl(&tree, i)
        try expect_kind(&result, declaration, .bool)
        try expect_kind(&result, ast.statement_decl(&tree, declaration).initializer, .bool)
        if (i < 3) continue
        comparison_view :: ast.binary_expr(&tree, ast.statement_decl(&tree, declaration).initializer)
        try expect_kind(&result, comparison_view.left, .float)
        try expect_kind(&result, comparison_view.right, .float)
    }
    for (usize(9)..usize(11)) |i| try expect_kind(&result, ast.package_decl(&tree, i), .float)
    identity :: ast.package_decl(&tree, 11)
    try expect_kind(&result, ast.param(&tree, ast.function_param(&tree, identity, 0)).type, .bool)
    try expect_kind(&result, ast.function_decl(&tree, identity).return_type, .bool)
    factorial :: ast.package_decl(&tree, 12)
    factorial_view :: ast.function_decl(&tree, factorial)
    try expect_kind(&result, factorial, .function)
    conditional :: ast.if_stmt(&tree, ast.block_statement(&tree, factorial_view.body, 0))
    try expect_kind(&result, conditional.condition, .bool)
    operands :: ast.binary_expr(&tree, conditional.condition)
    try expect_kind(&result, operands.left, .int)
    try expect_kind(&result, operands.right, .int)
    fraction :: ast.function_decl(&tree, ast.package_decl(&tree, 13))
    arms :: ast.if_stmt(&tree, ast.block_statement(&tree, fraction.body, 0))
    for (0..usize(2)) |i| {
        declaration :: ast.block_statement(&tree, arms.then_block, i)
        try expect_kind(&result, declaration, .float)
        try expect_kind(&result, ast.statement_decl(&tree, declaration).initializer, .float)
    }
    if (arms.else_block) |other| {
        nested :: ast.if_stmt(&tree, ast.block_statement(&tree, other, 0))
        try expect_kind(&result, ast.block_statement(&tree, nested.then_block, 0), .float)
    } else {
        return .expectation_failed
    }
    try testing.expect_equal(0, diagnostics.count(&diagnostic_store))
}

rejects_bool_numeric_mixing_and_preserves_invalid_condition_identity test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `sum :: true + false
        `order :: true < false
        `mixed :: true == 1
        `strings :: "x" == "x"
        `wrong_bool bool :: 1
        `wrong_int int :: false
        `main proc() void {
        `    if (1) { okay :: true }
        `    if "text" { okay :: false }
        `    if absent { okay :: true }
        `    if true + false { okay :: false }
        `    if true { return } else { -"bad" }
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    for (0..usize(4)) |i| {
        expression :: ast.statement_decl(&tree, ast.package_decl(&tree, i)).initializer
        _ = try expect_error(&result, &diagnostic_store, expression, .invalid_operand, ast.node_span(&tree, expression))
    }
    for (usize(4)..usize(6)) |i| {
        expression :: ast.statement_decl(&tree, ast.package_decl(&tree, i)).initializer
        _ = try expect_error(&result, &diagnostic_store, expression, .type_mismatch, ast.node_span(&tree, expression))
    }
    function :: ast.package_decl(&tree, 6)
    body :: ast.function_decl(&tree, function).body
    for (0..usize(2)) |i| {
        statement :: ast.block_statement(&tree, body, i)
        condition :: ast.if_stmt(&tree, statement).condition
        diagnostic :: try expect_error(&result, &diagnostic_store, condition, .condition_not_bool, ast.node_span(&tree, condition))
        try testing.expect_equal(diagnostic, type_of(&result, statement).diagnostic)
    }
    unknown :: ast.if_stmt(&tree, ast.block_statement(&tree, body, 2)).condition
    original :: sema.binding(&resolution, unknown).data.diagnostic
    try testing.expect_equal(original, type_of(&result, unknown).diagnostic)
    failed :: ast.if_stmt(&tree, ast.block_statement(&tree, body, 3)).condition
    _ = try expect_error(&result, &diagnostic_store, failed, .invalid_operand, ast.node_span(&tree, failed))
    final_if :: ast.block_statement(&tree, body, 4)
    try expect_kind(&result, final_if, .void)
    final_view :: ast.if_stmt(&tree, final_if)
    if (final_view.else_block) |other| {
        error_expr :: ast.statement_expr(&tree, ast.block_statement(&tree, other, 0))
        _ = try expect_error(&result, &diagnostic_store, error_expr, .invalid_operand, ast.node_span(&tree, error_expr))
    } else {
        return .expectation_failed
    }
    try expect_kind(&result, function, .function)
    try testing.expect_equal(2, code_count(&diagnostic_store, .condition_not_bool))
    try testing.expect_equal(6, code_count(&diagnostic_store, .invalid_operand))
    try testing.expect_equal(2, code_count(&diagnostic_store, .type_mismatch))
    try testing.expect_equal(1, code_count(&diagnostic_store, .unknown_name))
    try testing.expect_equal(11, diagnostics.count(&diagnostic_store))
}

analyzes_return_paths_after_trap_propagation_without_poisoning_signatures test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `both proc(flag bool) int {
        `    if flag { return 1 } else { return 2 }
        `}
        `missing proc() int { if true { return 1 } }
        `bad_arm proc(flag bool) int { if flag { -"bad" } }
        `trap_and_return proc(flag bool) int {
        `    if flag { return 1 } else { bad int :: false }
        `}
        `invalid_condition proc() int { if 1 {} }
        `invalid_expression proc() int { -"bad" }
        `invalid_declaration proc() int { bad bool :: 1 }
        `syntax_trap proc() int {
        `    return 1 stray
        `}
        `after_return proc() int {
        `    return 1
        `    -"bad"
        `}
        `nested proc(a bool, b bool) int {
        `    if a { if b { return 1 } else { return 2 } } else { return 3 }
        `}
        `join proc(flag bool) int {
        `    if flag {} else { return 1 }
        `    return 2
        `}
        `answer :: bad_arm(false)
        `wrong_return proc(flag bool) int {
        `    if flag { return false } else { return 1 }
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    for (0..usize(11)) |i| try expect_kind(&result, ast.package_decl(&tree, i), .function)
    for (usize(1)..usize(3)) |i| {
        function :: ast.package_decl(&tree, i)
        body :: ast.function_decl(&tree, function).body
        _ = try expect_fallthrough(&result, &diagnostic_store, function, ast.node_span(&tree, body))
    }
    bad_body :: ast.function_decl(&tree, ast.package_decl(&tree, 2)).body
    conditional :: ast.block_statement(&tree, bad_body, 0)
    try expect_kind(&result, conditional, .void)
    arm :: ast.if_stmt(&tree, conditional).then_block
    operand :: ast.statement_expr(&tree, ast.block_statement(&tree, arm, 0))
    original :: try expect_error(&result, &diagnostic_store, operand, .invalid_operand, ast.node_span(&tree, operand))
    try testing.expect_equal(original, type_of(&result, arm).diagnostic)
    try testing.expect(fallthrough_diagnostic(&result, ast.package_decl(&tree, 2))? != original)
    condition_body :: ast.function_decl(&tree, ast.package_decl(&tree, 4)).body
    condition :: ast.if_stmt(&tree, ast.block_statement(&tree, condition_body, 0)).condition
    condition_diag :: try expect_error(&result, &diagnostic_store, condition, .condition_not_bool, ast.node_span(&tree, condition))
    try testing.expect_equal(condition_diag, type_of(&result, condition_body).diagnostic)
    recovered :: ast.function_decl(&tree, ast.package_decl(&tree, 7)).body
    syntax :: ast.block_statement(&tree, recovered, 0)
    try testing.expect_equal(ast.invalid(&tree, syntax).diagnostic, type_of(&result, recovered).diagnostic)
    unreachable_body :: ast.function_decl(&tree, ast.package_decl(&tree, 8)).body
    checked_after_return :: ast.statement_expr(&tree, ast.block_statement(&tree, unreachable_body, 1))
    _ = try expect_error(&result, &diagnostic_store, checked_after_return, .invalid_operand, ast.node_span(&tree, checked_after_return))
    try expect_kind(&result, ast.package_decl(&tree, 11), .int)
    wrong_function :: ast.package_decl(&tree, 12)
    try expect_kind(&result, wrong_function, .function)
    wrong_body :: ast.function_decl(&tree, wrong_function).body
    wrong_if :: ast.block_statement(&tree, wrong_body, 0)
    try expect_kind(&result, wrong_if, .void)
    wrong_arm :: ast.if_stmt(&tree, wrong_if).then_block
    wrong_statement :: ast.block_statement(&tree, wrong_arm, 0)
    if (ast.return_stmt(&tree, wrong_statement).value) |value| {
        mismatch :: try expect_error(&result, &diagnostic_store, value, .return_type_mismatch, ast.node_span(&tree, value))
        try testing.expect_equal(mismatch, type_of(&result, wrong_statement).diagnostic)
        try testing.expect_equal(mismatch, type_of(&result, wrong_body).diagnostic)
    } else {
        return .expectation_failed
    }
    for 0..ast.package_decl_count(&tree) |i| {
        function :: ast.package_decl(&tree, i)
        if (i == 1 or i == 2 or ast.decl_kind(&tree, function) != .function) continue
        try testing.expect_equal(null, fallthrough_diagnostic(&result, function))
    }
    try testing.expect_equal(1, code_count(&diagnostic_store, .return_type_mismatch))
    try testing.expect_equal(2, code_count(&diagnostic_store, .missing_return))
    try testing.expect_equal(1, code_count(&diagnostic_store, .condition_not_bool))
}

assignments_preserve_established_types_and_contextualize_numeric_values test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `take_float proc(value float) int { return 1 }
        `main proc() void {
        `    number := 0
        `    number = 1.5
        `    number = number + 1.5
        `    number = take_float(number)
        `    observed :: number
        `    quotient float := 0
        `    quotient = 3 / 2
        `    inferred := 0
        `    context float :: inferred
        `    inferred = 5 / 2
        `    rigid int := 1
        `    quotient = rigid
        `    flag := true
        `    flag = false
        `    text := "before"
        `    text = "after"
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    try testing.expect_equal(0, diagnostics.count(&diagnostic_store))
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    body :: ast.function_decl(&tree, ast.package_decl(&tree, 1)).body
    number :: ast.block_statement(&tree, body, 0)
    observed :: ast.block_statement(&tree, body, 4)
    quotient :: ast.block_statement(&tree, body, 5)
    inferred :: ast.block_statement(&tree, body, 7)
    rigid :: ast.block_statement(&tree, body, 10)
    declarations [3]ast.NodeId :: [number, observed, rigid]
    for declarations |id| {
        try expect_kind(&result, id, .int)
        try expect_kind(&result, ast.statement_decl(&tree, id).initializer, .int)
    }
    try expect_kind(&result, quotient, .float)
    try expect_kind(&result, inferred, .float)
    bad_values [2]usize :: [1, 11]
    for bad_values |index| {
        statement :: ast.block_statement(&tree, body, index)
        assignment :: ast.assignment_stmt(&tree, statement)
        original :: try expect_error(&result, &diagnostic_store, assignment.value, .type_mismatch, ast.node_span(&tree, assignment.value))
        try testing.expect_equal(original, type_of(&result, statement).diagnostic)
        expected :: if (index == 1) TypeKind.int else TypeKind.float
        try expect_kind(&result, assignment.target, expected)
    }
    arithmetic_statement :: ast.block_statement(&tree, body, 2)
    arithmetic :: ast.assignment_stmt(&tree, arithmetic_statement)
    original :: try expect_error(&result, &diagnostic_store, arithmetic.value, .invalid_operand, ast.node_span(&tree, arithmetic.value))
    try testing.expect_equal(original, type_of(&result, arithmetic_statement).diagnostic)
    try expect_kind(&result, arithmetic.target, .int)
    try expect_kind(&result, ast.binary_expr(&tree, arithmetic.value).left, .int)
    call_statement :: ast.block_statement(&tree, body, 3)
    call :: ast.assignment_stmt(&tree, call_statement)
    argument :: ast.call_arg(&tree, call.value, 0)
    call_error :: try expect_error(&result, &diagnostic_store, argument, .type_mismatch, ast.node_span(&tree, argument))
    try testing.expect_equal(call_error, type_of(&result, call_statement).diagnostic)
    try expect_kind(&result, call.target, .int)
    divisions [2]usize :: [6, 9]
    for divisions |index| {
        statement :: ast.block_statement(&tree, body, index)
        assignment :: ast.assignment_stmt(&tree, statement)
        division :: ast.binary_expr(&tree, assignment.value)
        try expect_kind(&result, statement, .void)
        try expect_kind(&result, assignment.target, .float)
        try expect_kind(&result, assignment.value, .float)
        try expect_kind(&result, division.left, .float)
        try expect_kind(&result, division.right, .float)
    }
    scalar_assignments [2]usize :: [13, 15]
    for scalar_assignments |index| {
        statement :: ast.block_statement(&tree, body, index)
        assignment :: ast.assignment_stmt(&tree, statement)
        expected :: if (index == 13) TypeKind.bool else TypeKind.string
        try expect_kind(&result, statement, .void)
        try expect_kind(&result, assignment.target, expected)
        try expect_kind(&result, assignment.value, expected)
    }
    try testing.expect_equal(3, code_count(&diagnostic_store, .type_mismatch))
    try testing.expect_equal(1, code_count(&diagnostic_store, .invalid_operand))
    try testing.expect_equal(0, code_count(&diagnostic_store, .integer_division))
}

assignment_target_errors_preserve_bindings_and_independent_rhs_diagnostics test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `global := 1
        `named proc() void {}
        `main proc(parameter int) void {
        `    constant :: 1
        `    constant = 2
        `    parameter = 2
        `    global = 2
        `    named = named
        `    int = 2
        `    absent = other_missing
        `    constant = -false
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    function :: ast.package_decl(&tree, 2)
    body :: ast.function_decl(&tree, function).body
    for usize(1)..usize(6) |index| {
        statement :: ast.block_statement(&tree, body, index)
        assignment :: ast.assignment_stmt(&tree, statement)
        _ = try expect_error(&result, &diagnostic_store, statement, .invalid_assignment_target, ast.node_span(&tree, assignment.target))
        expected :: if (index == 4) TypeKind.function else TypeKind.int
        try expect_kind(&result, assignment.value, expected)
        if (index != 5) try testing.expect(type_of(&result, assignment.target).kind != .invalid)
    }
    unknown_statement :: ast.block_statement(&tree, body, 6)
    unknown :: ast.assignment_stmt(&tree, unknown_statement)
    target_error :: sema.binding(&resolution, unknown.target).data.diagnostic
    value_error :: sema.binding(&resolution, unknown.value).data.diagnostic
    try testing.expect(target_error != value_error)
    try testing.expect_equal(target_error, type_of(&result, unknown.target).diagnostic)
    try testing.expect_equal(target_error, type_of(&result, unknown_statement).diagnostic)
    try testing.expect_equal(value_error, type_of(&result, unknown.value).diagnostic)
    independent_statement :: ast.block_statement(&tree, body, 7)
    independent :: ast.assignment_stmt(&tree, independent_statement)
    _ = try expect_error(&result, &diagnostic_store, independent.value, .invalid_operand, ast.node_span(&tree, independent.value))
    _ = try expect_error(&result, &diagnostic_store, independent_statement, .invalid_assignment_target, ast.node_span(&tree, independent.target))
    try expect_kind(&result, ast.block_statement(&tree, body, 0), .int)
    try expect_kind(&result, ast.function_param(&tree, function, 0), .int)
    try expect_kind(&result, ast.package_decl(&tree, 0), .int)
    try expect_kind(&result, ast.package_decl(&tree, 1), .function)
    try testing.expect_equal(6, code_count(&diagnostic_store, .invalid_assignment_target))
    try testing.expect_equal(2, code_count(&diagnostic_store, .unknown_name))
    try testing.expect_equal(0, code_count(&diagnostic_store, .type_not_value))
}

function_assignment_checks_complete_signatures_without_retargeting_calls test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `first proc(a int) int { return a }
        `same proc(renamed int) int { return renamed + 1 }
        `wrong_parameter proc(a float) int { return 1 }
        `wrong_result proc(a int) bool { return true }
        `wrong_count proc() int { return 2 }
        `main proc() int {
        `    chosen := first
        `    chosen = same
        `    chosen = wrong_parameter
        `    chosen = wrong_result
        `    chosen = wrong_count
        `    answer :: chosen(7)
        `    return answer
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    try testing.expect_equal(0, diagnostics.count(&diagnostic_store))
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    first :: ast.package_decl(&tree, 0)
    body :: ast.function_decl(&tree, ast.package_decl(&tree, 5)).body
    chosen :: ast.block_statement(&tree, body, 0)
    try expect_kind(&result, chosen, .function)
    try testing.expect_equal(first, type_of(&result, chosen).function)
    try expect_kind(&result, ast.block_statement(&tree, body, 1), .void)
    for usize(2)..usize(5) |index| {
        statement :: ast.block_statement(&tree, body, index)
        assignment :: ast.assignment_stmt(&tree, statement)
        original :: try expect_error(&result, &diagnostic_store, assignment.value, .type_mismatch, ast.node_span(&tree, assignment.value))
        try testing.expect_equal(original, type_of(&result, statement).diagnostic)
        try expect_kind(&result, assignment.target, .function)
        try testing.expect_equal(first, type_of(&result, assignment.target).function)
    }
    answer :: ast.block_statement(&tree, body, 5)
    call :: ast.statement_decl(&tree, answer).initializer
    try expect_kind(&result, answer, .int)
    try expect_kind(&result, call, .int)
    try testing.expect_equal(first, type_of(&result, ast.call_expr(&tree, call).callee).function)
    try testing.expect_equal(3, code_count(&diagnostic_store, .type_mismatch))
    try testing.expect_equal(0, code_count(&diagnostic_store, .argument_count_mismatch))
}

while_checks_nested_bodies_without_claiming_a_zero_iteration_return test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `terminal proc() int { while true { return 1 } }
        `bad_body proc() int { while false { -"bad" } }
        `continues proc() int {
        `    while false { -"bad" }
        `    return 7
        `}
        `bad_condition proc() int { while 1 { -"bad" } }
        `unknown_condition proc() int { while absent { missing_body } }
        `nested proc() void {
        `    counter := 2
        `    while counter > 0 {
        `        inner := 1
        `        while inner > 0 {
        `            inner = inner - 1
        `            counter = counter - 1
        `        }
        `    }
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    terminal :: ast.package_decl(&tree, 0)
    try testing.expect(fallthrough_diagnostic(&result, terminal) == null)
    body :: ast.function_decl(&tree, ast.package_decl(&tree, 1)).body
    _ = try expect_fallthrough(&result, &diagnostic_store, ast.package_decl(&tree, 1), ast.node_span(&tree, body))
    try expect_kind(&result, ast.block_statement(&tree, body, 0), .void)
    continues_body :: ast.function_decl(&tree, ast.package_decl(&tree, 2)).body
    loop_statement :: ast.block_statement(&tree, continues_body, 0)
    loop :: ast.while_stmt(&tree, loop_statement)
    invalid_body :: ast.statement_expr(&tree, ast.block_statement(&tree, loop.body, 0))
    original :: try expect_error(&result, &diagnostic_store, invalid_body, .invalid_operand, ast.node_span(&tree, invalid_body))
    try testing.expect_equal(original, type_of(&result, loop.body).diagnostic)
    try testing.expect_equal(original, type_of(&result, continues_body).diagnostic)
    try expect_kind(&result, loop_statement, .void)
    try expect_kind(&result, ast.block_statement(&tree, continues_body, 1), .void)
    bad_condition_body :: ast.function_decl(&tree, ast.package_decl(&tree, 3)).body
    bad_condition_statement :: ast.block_statement(&tree, bad_condition_body, 0)
    condition :: ast.while_stmt(&tree, bad_condition_statement).condition
    condition_error :: try expect_error(&result, &diagnostic_store, condition, .condition_not_bool, ast.node_span(&tree, condition))
    try testing.expect_equal(condition_error, type_of(&result, bad_condition_statement).diagnostic)
    unknown_body :: ast.function_decl(&tree, ast.package_decl(&tree, 4)).body
    unknown_statement :: ast.block_statement(&tree, unknown_body, 0)
    unknown :: ast.while_stmt(&tree, unknown_statement).condition
    try testing.expect_equal(sema.binding(&resolution, unknown).data.diagnostic, type_of(&result, unknown_statement).diagnostic)
    nested_body :: ast.function_decl(&tree, ast.package_decl(&tree, 5)).body
    try expect_kind(&result, nested_body, .none)
    outer_loop :: ast.while_stmt(&tree, ast.block_statement(&tree, nested_body, 1))
    inner_loop :: ast.while_stmt(&tree, ast.block_statement(&tree, outer_loop.body, 1))
    for usize(0)..usize(2) |index| {
        statement :: ast.block_statement(&tree, inner_loop.body, index)
        assignment :: ast.assignment_stmt(&tree, statement)
        try expect_kind(&result, statement, .void)
        try expect_kind(&result, assignment.target, .int)
        try expect_kind(&result, assignment.value, .int)
    }
    try testing.expect_equal(1, code_count(&diagnostic_store, .missing_return))
    try testing.expect_equal(1, code_count(&diagnostic_store, .condition_not_bool))
    try testing.expect_equal(3, code_count(&diagnostic_store, .invalid_operand))
}

logical_types_preserve_comparison_context_and_assignment_isolation test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `seed :: 3
        `forward :: seed
        `composed :: !(forward < 4.0) and true or false
        `equal :: !(true and false) == (true or false)
        `nested :: !!!true
        `identity proc(value bool) bool { return value }
        `main proc() bool {
        `    count := 1
        `    flag := true
        `    flag = !(count < 2) and identity(true) or false
        `    return flag
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    for (usize(0)..usize(2)) |index| try expect_kind(&result, ast.package_decl(&tree, index), .float)
    for usize(2)..usize(5) |index| {
        declaration :: ast.package_decl(&tree, index)
        try expect_kind(&result, declaration, .bool)
        try expect_kind(&result, ast.statement_decl(&tree, declaration).initializer, .bool)
    }
    composed :: ast.binary_expr(&tree, ast.statement_decl(&tree, ast.package_decl(&tree, 2)).initializer)
    try testing.expect_equal(ast.BinaryOperator.logical_or, composed.operator)
    conjunction :: ast.binary_expr(&tree, composed.left)
    try testing.expect_equal(ast.BinaryOperator.logical_and, conjunction.operator)
    inverted :: ast.unary_expr(&tree, conjunction.left)
    try expect_kind(&result, conjunction.left, .bool)
    comparison_view :: ast.binary_expr(&tree, inverted.operand)
    try expect_kind(&result, comparison_view.left, .float)
    try expect_kind(&result, comparison_view.right, .float)
    nested := ast.statement_decl(&tree, ast.package_decl(&tree, 4)).initializer
    for 0..3 |_| {
        try expect_kind(&result, nested, .bool)
        view :: ast.unary_expr(&tree, nested)
        try testing.expect_equal(ast.UnaryOperator.logical_not, view.operator)
        nested = view.operand
    }
    try expect_kind(&result, nested, .bool)
    body :: ast.function_decl(&tree, ast.package_decl(&tree, 6)).body
    count :: ast.block_statement(&tree, body, 0)
    try expect_kind(&result, count, .int)
    assignment :: ast.assignment_stmt(&tree, ast.block_statement(&tree, body, 2))
    try expect_kind(&result, assignment.value, .bool)
    disjunction :: ast.binary_expr(&tree, assignment.value)
    assignment_conjunction :: ast.binary_expr(&tree, disjunction.left)
    assignment_not :: ast.unary_expr(&tree, assignment_conjunction.left)
    assignment_comparison :: ast.binary_expr(&tree, assignment_not.operand)
    try expect_kind(&result, assignment_comparison.left, .int)
    try expect_kind(&result, assignment_comparison.right, .int)
    try testing.expect_equal(0, diagnostics.count(&diagnostic_store))
}

logical_operand_errors_are_independent_and_skipped_rhs_preserves_bool test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `number :: 1
        `number_alias :: number
        `skipped_unknown :: false and absent
        `skipped_kind :: true or number
        `both_bad :: 1 and "wrong"
        `demanded_unknown :: missing or true
        `demanded_not :: !number_alias
        `nested :: !(false and absent_nested) == true
        `independent :: left_missing and 1
        `identity proc(value bool) bool { return value }
        `skips proc() bool {
        `    local :: true or 1
        `    value := false
        `    value = false and absent_assignment
        `    identity(true or absent_argument)
        `    if true or 1 { value = true }
        `    while false and 1 { value = false }
        `    return false and absent_return
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    for usize(0)..usize(2) |index| {
        declaration :: ast.package_decl(&tree, index)
        try expect_kind(&result, declaration, .int)
        try expect_kind(&result, ast.statement_decl(&tree, declaration).initializer, .int)
    }
    skipped_indices [3]usize :: [2, 3, 7]
    for skipped_indices |index| {
        declaration :: ast.package_decl(&tree, index)
        try expect_kind(&result, declaration, .bool)
        try expect_kind(&result, ast.statement_decl(&tree, declaration).initializer, .bool)
    }
    unknown :: ast.binary_expr(&tree, ast.statement_decl(&tree, ast.package_decl(&tree, 2)).initializer)
    try testing.expect_equal(sema.binding(&resolution, unknown.right).data.diagnostic, type_of(&result, unknown.right).diagnostic)
    _ = try expect_error(&result, &diagnostic_store, unknown.right, .unknown_name, ast.node_span(&tree, unknown.right))
    wrong :: ast.binary_expr(&tree, ast.statement_decl(&tree, ast.package_decl(&tree, 3)).initializer)
    _ = try expect_error(&result, &diagnostic_store, wrong.right, .invalid_operand, ast.node_span(&tree, wrong.right))
    both_declaration :: ast.package_decl(&tree, 4)
    both_id :: ast.statement_decl(&tree, both_declaration).initializer
    both :: ast.binary_expr(&tree, both_id)
    left_error :: try expect_error(&result, &diagnostic_store, both.left, .invalid_operand, ast.node_span(&tree, both.left))
    right_error :: try expect_error(&result, &diagnostic_store, both.right, .invalid_operand, ast.node_span(&tree, both.right))
    try testing.expect(left_error != right_error)
    try testing.expect_equal(left_error, type_of(&result, both_id).diagnostic)
    try testing.expect_equal(left_error, type_of(&result, both_declaration).diagnostic)
    demanded_id :: ast.statement_decl(&tree, ast.package_decl(&tree, 5)).initializer
    demanded :: ast.binary_expr(&tree, demanded_id)
    try testing.expect_equal(sema.binding(&resolution, demanded.left).data.diagnostic, type_of(&result, demanded_id).diagnostic)
    not_id :: ast.statement_decl(&tree, ast.package_decl(&tree, 6)).initializer
    not_view :: ast.unary_expr(&tree, not_id)
    not_error :: try expect_error(&result, &diagnostic_store, not_view.operand, .invalid_operand, ast.node_span(&tree, not_view.operand))
    try testing.expect_equal(not_error, type_of(&result, not_id).diagnostic)
    independent_id :: ast.statement_decl(&tree, ast.package_decl(&tree, 8)).initializer
    independent :: ast.binary_expr(&tree, independent_id)
    try testing.expect_equal(sema.binding(&resolution, independent.left).data.diagnostic, type_of(&result, independent_id).diagnostic)
    _ = try expect_error(&result, &diagnostic_store, independent.right, .invalid_operand, ast.node_span(&tree, independent.right))
    body :: ast.function_decl(&tree, ast.package_decl(&tree, 10)).body
    try expect_kind(&result, body, .none)
    try expect_kind(&result, ast.block_statement(&tree, body, 0), .bool)
    assignment_id :: ast.block_statement(&tree, body, 2)
    assignment :: ast.assignment_stmt(&tree, assignment_id)
    try expect_kind(&result, assignment_id, .void)
    try expect_kind(&result, assignment.value, .bool)
    call :: ast.statement_expr(&tree, ast.block_statement(&tree, body, 3))
    try expect_kind(&result, call, .bool)
    try expect_kind(&result, ast.call_arg(&tree, call, 0), .bool)
    conditional :: ast.if_stmt(&tree, ast.block_statement(&tree, body, 4))
    loop :: ast.while_stmt(&tree, ast.block_statement(&tree, body, 5))
    try expect_kind(&result, conditional.condition, .bool)
    try expect_kind(&result, loop.condition, .bool)
    returned :: ast.block_statement(&tree, body, 6)
    try expect_kind(&result, returned, .void)
    if (ast.return_stmt(&tree, returned).value) |value| try expect_kind(&result, value, .bool)
    else return .expectation_failed
    try testing.expect_equal(7, code_count(&diagnostic_store, .unknown_name))
    try testing.expect_equal(8, code_count(&diagnostic_store, .invalid_operand))
    try testing.expect_equal(15, diagnostics.count(&diagnostic_store))
}

logical_external_mismatches_and_always_demanded_not_preserve_errors test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `accept_bool proc(value bool) bool { return value }
        `accept_int proc(value int) bool { return true }
        `noop proc() void {}
        `wrong_decl int :: true or 1
        `wrong_return proc() int { return false and absent_return }
        `wrong_argument proc() bool { return accept_int(false and absent_argument) }
        `wrong_assignment proc() void {
        `    count := 1
        `    count = true or 1
        `}
        `unary_bad proc() void {
        `    !1.0
        `    !"text"
        `    !accept_bool
        `    !noop()
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    declaration :: ast.package_decl(&tree, 3)
    initializer :: ast.statement_decl(&tree, declaration).initializer
    declaration_error :: try expect_error(&result, &diagnostic_store, initializer, .type_mismatch, ast.node_span(&tree, initializer))
    try testing.expect_equal(declaration_error, type_of(&result, declaration).diagnostic)
    return_body :: ast.function_decl(&tree, ast.package_decl(&tree, 4)).body
    return_id :: ast.block_statement(&tree, return_body, 0)
    if (ast.return_stmt(&tree, return_id).value) |value| {
        return_error :: try expect_error(&result, &diagnostic_store, value, .return_type_mismatch, ast.node_span(&tree, value))
        try testing.expect_equal(return_error, type_of(&result, return_id).diagnostic)
        operand :: ast.binary_expr(&tree, value).right
        try testing.expect_equal(sema.binding(&resolution, operand).data.diagnostic, type_of(&result, operand).diagnostic)
        try testing.expect(return_error != type_of(&result, operand).diagnostic)
    } else {
        return .expectation_failed
    }
    argument_body :: ast.function_decl(&tree, ast.package_decl(&tree, 5)).body
    argument_return :: ast.block_statement(&tree, argument_body, 0)
    if (ast.return_stmt(&tree, argument_return).value) |call| {
        argument :: ast.call_arg(&tree, call, 0)
        argument_error :: try expect_error(&result, &diagnostic_store, argument, .type_mismatch, ast.node_span(&tree, argument))
        try testing.expect_equal(argument_error, type_of(&result, call).diagnostic)
        try testing.expect_equal(argument_error, type_of(&result, argument_return).diagnostic)
    } else {
        return .expectation_failed
    }
    assignment_body :: ast.function_decl(&tree, ast.package_decl(&tree, 6)).body
    assignment_id :: ast.block_statement(&tree, assignment_body, 1)
    assignment :: ast.assignment_stmt(&tree, assignment_id)
    assignment_error :: try expect_error(&result, &diagnostic_store, assignment.value, .type_mismatch, ast.node_span(&tree, assignment.value))
    try testing.expect_equal(assignment_error, type_of(&result, assignment_id).diagnostic)
    try expect_kind(&result, assignment.target, .int)
    try expect_kind(&result, ast.block_statement(&tree, assignment_body, 0), .int)
    unary_body :: ast.function_decl(&tree, ast.package_decl(&tree, 7)).body
    for usize(0)..usize(4) |index| {
        expression :: ast.statement_expr(&tree, ast.block_statement(&tree, unary_body, index))
        operand :: ast.unary_expr(&tree, expression).operand
        original :: try expect_error(&result, &diagnostic_store, operand, .invalid_operand, ast.node_span(&tree, operand))
        try testing.expect_equal(original, type_of(&result, expression).diagnostic)
    }
    for (usize(0)..usize(3)) |index| try expect_kind(&result, ast.package_decl(&tree, index), .function)
    try testing.expect_equal(6, code_count(&diagnostic_store, .invalid_operand))
    try testing.expect_equal(2, code_count(&diagnostic_store, .unknown_name))
    try testing.expect_equal(3, code_count(&diagnostic_store, .type_mismatch))
    try testing.expect_equal(1, code_count(&diagnostic_store, .return_type_mismatch))
    try testing.expect_equal(12, diagnostics.count(&diagnostic_store))
}

short_circuit_skip_paths_do_not_guarantee_a_return test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `expression proc() int { false and missing_expression }
        `declaration proc() int { local :: true or 1 }
        `assignment proc() int {
        `    value := false
        `    value = false and missing_assignment
        `}
        `call proc() int { take(true or 1) }
        `conditional proc() int { if false and missing_condition { return 1 } }
        `loop proc() int { while true or missing_guard { return 1 } }
        `loop_body proc(flag bool) int { while flag { true or 1 } }
        `arms proc(flag bool) int {
        `    if flag { false and missing_arm } else { return 1 }
        `}
        `demanded proc() int { missing_left or true }
        `successful proc() bool { return true or missing_return }
        `take proc(value bool) void {}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    for usize(0)..usize(8) |index| {
        function :: ast.package_decl(&tree, index)
        try expect_kind(&result, function, .function)
        body :: ast.function_decl(&tree, function).body
        _ = try expect_fallthrough(&result, &diagnostic_store, function, ast.node_span(&tree, body))
    }
    expression_body :: ast.function_decl(&tree, ast.package_decl(&tree, 0)).body
    expression :: ast.statement_expr(&tree, ast.block_statement(&tree, expression_body, 0))
    try expect_kind(&result, expression, .bool)
    loop_body :: ast.function_decl(&tree, ast.package_decl(&tree, 6)).body
    loop_id :: ast.block_statement(&tree, loop_body, 0)
    try expect_kind(&result, loop_id, .void)
    demanded_body :: ast.function_decl(&tree, ast.package_decl(&tree, 8)).body
    demanded :: ast.statement_expr(&tree, ast.block_statement(&tree, demanded_body, 0))
    left :: ast.binary_expr(&tree, demanded).left
    original :: sema.binding(&resolution, left).data.diagnostic
    try testing.expect_equal(original, type_of(&result, demanded).diagnostic)
    try testing.expect_equal(original, type_of(&result, demanded_body).diagnostic)
    successful_body :: ast.function_decl(&tree, ast.package_decl(&tree, 9)).body
    try expect_kind(&result, successful_body, .none)
    try expect_kind(&result, ast.block_statement(&tree, successful_body, 0), .void)
    try testing.expect_equal(8, code_count(&diagnostic_store, .missing_return))
    try testing.expect_equal(7, code_count(&diagnostic_store, .unknown_name))
    try testing.expect_equal(3, code_count(&diagnostic_store, .invalid_operand))
    try testing.expect_equal(18, diagnostics.count(&diagnostic_store))
}

loop_controls_follow_lexical_bodies_and_check_unreachable_code test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `scopes proc(flag bool) void {
        `    while flag {
        `        if (flag) break else continue
        `        while flag {
        `            if (flag) continue else break
        `        }
        `        absent
        `    }
        `    break
        `    continue
        `}
        `caller proc() void {
        `    while true {
        `        callee()
        `        break
        `    }
        `}
        `callee proc() void { continue }
        `dead proc() void {
        `    return
        `    break
        `    continue
        `}
        `arms proc() void {
        `    if (false) break else continue
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    scopes_body :: ast.function_decl(&tree, ast.package_decl(&tree, 0)).body
    outer_statement :: ast.block_statement(&tree, scopes_body, 0)
    outer :: ast.while_stmt(&tree, outer_statement)
    outer_if :: ast.if_stmt(&tree, ast.block_statement(&tree, outer.body, 0))
    inner_statement :: ast.block_statement(&tree, outer.body, 1)
    inner :: ast.while_stmt(&tree, inner_statement)
    inner_if :: ast.if_stmt(&tree, ast.block_statement(&tree, inner.body, 0))
    caller_body :: ast.function_decl(&tree, ast.package_decl(&tree, 1)).body
    caller_loop :: ast.while_stmt(&tree, ast.block_statement(&tree, caller_body, 0))
    valid [5]ast.NodeId :: [
        ast.block_statement(&tree, outer_if.then_block, 0),
        ast.block_statement(&tree, outer_if.else_block?, 0),
        ast.block_statement(&tree, inner_if.then_block, 0),
        ast.block_statement(&tree, inner_if.else_block?, 0),
        ast.block_statement(&tree, caller_loop.body, 1),
    ]
    for (valid) |statement| try expect_kind(&result, statement, .void)
    try expect_kind(&result, outer_statement, .void)
    try expect_kind(&result, inner_statement, .void)
    unknown :: ast.statement_expr(&tree, ast.block_statement(&tree, outer.body, 2))
    original :: sema.binding(&resolution, unknown).data.diagnostic
    try testing.expect_equal(original, type_of(&result, unknown).diagnostic)
    outside_break :: ast.block_statement(&tree, scopes_body, 1)
    outside_continue :: ast.block_statement(&tree, scopes_body, 2)
    _ = try expect_error(&result, &diagnostic_store, outside_break, .break_outside_loop, ast.node_span(&tree, outside_break))
    _ = try expect_error(&result, &diagnostic_store, outside_continue, .continue_outside_loop, ast.node_span(&tree, outside_continue))
    callee_body :: ast.function_decl(&tree, ast.package_decl(&tree, 2)).body
    callee_control :: ast.block_statement(&tree, callee_body, 0)
    _ = try expect_error(&result, &diagnostic_store, callee_control, .continue_outside_loop, ast.node_span(&tree, callee_control))
    dead_body :: ast.function_decl(&tree, ast.package_decl(&tree, 3)).body
    dead_break :: ast.block_statement(&tree, dead_body, 1)
    dead_continue :: ast.block_statement(&tree, dead_body, 2)
    _ = try expect_error(&result, &diagnostic_store, dead_break, .break_outside_loop, ast.node_span(&tree, dead_break))
    _ = try expect_error(&result, &diagnostic_store, dead_continue, .continue_outside_loop, ast.node_span(&tree, dead_continue))
    arms_body :: ast.function_decl(&tree, ast.package_decl(&tree, 4)).body
    arms :: ast.if_stmt(&tree, ast.block_statement(&tree, arms_body, 0))
    arm_break :: ast.block_statement(&tree, arms.then_block, 0)
    arm_continue :: ast.block_statement(&tree, arms.else_block?, 0)
    _ = try expect_error(&result, &diagnostic_store, arm_break, .break_outside_loop, ast.node_span(&tree, arm_break))
    _ = try expect_error(&result, &diagnostic_store, arm_continue, .continue_outside_loop, ast.node_span(&tree, arm_continue))
    for (usize(0)..usize(5)) |index| try expect_kind(&result, ast.package_decl(&tree, index), .function)
    try testing.expect_equal(3, code_count(&diagnostic_store, .break_outside_loop))
    try testing.expect_equal(4, code_count(&diagnostic_store, .continue_outside_loop))
    try testing.expect_equal(1, code_count(&diagnostic_store, .unknown_name))
    try testing.expect_equal(8, diagnostics.count(&diagnostic_store))
}

loop_controls_do_not_guarantee_function_returns test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `breaking proc() int { while true { break } }
        `continuing proc() int { while false { continue } }
        `mixed proc(flag bool) int {
        `    while flag {
        `        if (flag) return 42 else break
        `    }
        `}
        `closed proc(flag bool) int {
        `    while flag {
        `        if (flag) break else continue
        `        -"bad"
        `    }
        `    return 42
        `}
        `invalid proc() int { break }
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    for (usize(0)..usize(3)) |index| {
        function :: ast.package_decl(&tree, index)
        body :: ast.function_decl(&tree, function).body
        _ = try expect_fallthrough(&result, &diagnostic_store, function, ast.node_span(&tree, body))
        try expect_kind(&result, ast.block_statement(&tree, body, 0), .void)
    }
    closed_body :: ast.function_decl(&tree, ast.package_decl(&tree, 3)).body
    loop_statement :: ast.block_statement(&tree, closed_body, 0)
    loop :: ast.while_stmt(&tree, loop_statement)
    dead_expression :: ast.statement_expr(&tree, ast.block_statement(&tree, loop.body, 1))
    original :: try expect_error(&result, &diagnostic_store, dead_expression, .invalid_operand, ast.node_span(&tree, dead_expression))
    try testing.expect_equal(original, type_of(&result, closed_body).diagnostic)
    try expect_kind(&result, loop_statement, .void)
    try expect_kind(&result, ast.block_statement(&tree, closed_body, 1), .void)
    invalid_body :: ast.function_decl(&tree, ast.package_decl(&tree, 4)).body
    invalid_control :: ast.block_statement(&tree, invalid_body, 0)
    control_error :: try expect_error(&result, &diagnostic_store, invalid_control, .break_outside_loop, ast.node_span(&tree, invalid_control))
    try testing.expect_equal(control_error, type_of(&result, invalid_body).diagnostic)
    for (usize(0)..usize(5)) |index| try expect_kind(&result, ast.package_decl(&tree, index), .function)
    try testing.expect_equal(3, code_count(&diagnostic_store, .missing_return))
    try testing.expect_equal(1, code_count(&diagnostic_store, .invalid_operand))
    try testing.expect_equal(1, code_count(&diagnostic_store, .break_outside_loop))
    try testing.expect_equal(5, diagnostics.count(&diagnostic_store))
}

range_bounds_receive_integer_context_without_joining_the_range_or_capture test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `limit :: seed
        `seed := 3
        `endpoint proc() int { return 4 }
        `consume proc(value int) void {}
        `main proc() void {
        `    for (-2)..(limit + 1) |item| {
        `        consume(item)
        `        copy :: item
        `        while false { consume(copy) }
        `    }
        `    for (0..=endpoint()) |_| consume(1)
        `    for 0..2 |item| { consume(item) }
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    try expect_kind(&result, ast.package_decl(&tree, 0), .int)
    try expect_kind(&result, ast.package_decl(&tree, 1), .int)
    main_body :: ast.function_decl(&tree, ast.package_decl(&tree, 4)).body
    for (usize(0)..usize(3)) |index| {
        statement :: ast.block_statement(&tree, main_body, index)
        loop :: ast.for_stmt(&tree, statement)
        range_view :: ast.range_expr(&tree, loop.iterable)
        try expect_kind(&result, statement, .void)
        try expect_kind(&result, loop.iterable, .range)
        try expect_kind(&result, range_view.start, .int)
        try expect_kind(&result, range_view.end, .int)
        if (loop.capture) |capture| {
            try expect_kind(&result, capture, .int)
            try testing.expect_equal(capture, sema.binding(&resolution, capture).data.declaration)
            call :: ast.statement_expr(&tree, ast.block_statement(&tree, loop.body, 0))
            item :: ast.call_arg(&tree, call, 0)
            try expect_kind(&result, item, .int)
            try testing.expect_equal(capture, sema.binding(&resolution, item).data.declaration)
        }
    }
    first :: ast.for_stmt(&tree, ast.block_statement(&tree, main_body, 0))
    first_range :: ast.range_expr(&tree, first.iterable)
    try expect_kind(&result, ast.unary_expr(&tree, first_range.start).operand, .int)
    upper :: ast.binary_expr(&tree, first_range.end)
    try expect_kind(&result, upper.left, .int)
    try expect_kind(&result, upper.right, .int)
    try expect_kind(&result, ast.block_statement(&tree, first.body, 1), .int)
    try testing.expect_equal(0, diagnostics.count(&diagnostic_store))
}

range_checks_both_bounds_and_preserves_fixed_declarations_and_source_errors test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `real float :: 2
        `flag :: true
        `forwarded :: flag
        `nothing proc() void {}
        `main proc() void {
        `    for 1.5..2.5 |_| {}
        `    for forwarded.."text" |_| {}
        `    for nothing..nothing() |_| {}
        `    for real..3 |_| {}
        `    for absent_start..absent_end |_| {}
        `    for 0..1 |_| { sibling :: 7 }
        `    for flexible..floating_alias |_| {}
        `}
        `floating float :: floating_alias
        `floating_alias :: flexible
        `flexible := 3
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    try expect_kind(&result, ast.package_decl(&tree, 0), .float)
    try expect_kind(&result, ast.package_decl(&tree, 1), .bool)
    try expect_kind(&result, ast.package_decl(&tree, 2), .bool)
    try expect_kind(&result, ast.package_decl(&tree, 3), .function)
    main_body :: ast.function_decl(&tree, ast.package_decl(&tree, 4)).body
    for (usize(0)..usize(3)) |index| {
        statement :: ast.block_statement(&tree, main_body, index)
        loop :: ast.for_stmt(&tree, statement)
        range_view :: ast.range_expr(&tree, loop.iterable)
        first_error :: try expect_error(&result, &diagnostic_store, range_view.start, .invalid_range_bound, ast.node_span(&tree, range_view.start))
        second_error :: try expect_error(&result, &diagnostic_store, range_view.end, .invalid_range_bound, ast.node_span(&tree, range_view.end))
        try testing.expect(first_error != second_error)
        try testing.expect_equal(type_of(&result, loop.iterable).diagnostic, type_of(&result, statement).diagnostic)
    }
    mixed :: ast.for_stmt(&tree, ast.block_statement(&tree, main_body, 3))
    mixed_range :: ast.range_expr(&tree, mixed.iterable)
    _ = try expect_error(&result, &diagnostic_store, mixed_range.start, .invalid_range_bound, ast.node_span(&tree, mixed_range.start))
    try expect_kind(&result, mixed_range.end, .int)
    unknown :: ast.for_stmt(&tree, ast.block_statement(&tree, main_body, 4))
    unknown_range :: ast.range_expr(&tree, unknown.iterable)
    unknown_bounds [2]ast.NodeId :: [unknown_range.start, unknown_range.end]
    for unknown_bounds |bound| {
        original :: sema.binding(&resolution, bound).data.diagnostic
        _ = try expect_error(&result, &diagnostic_store, bound, .unknown_name, ast.node_span(&tree, bound))
        try testing.expect_equal(original, type_of(&result, bound).diagnostic)
    }
    sibling :: ast.for_stmt(&tree, ast.block_statement(&tree, main_body, 5))
    try expect_kind(&result, sibling.iterable, .range)
    try expect_kind(&result, ast.block_statement(&tree, sibling.body, 0), .int)
    floating_loop :: ast.for_stmt(&tree, ast.block_statement(&tree, main_body, 6))
    floating_range :: ast.range_expr(&tree, floating_loop.iterable)
    floating_start_error :: try expect_error(&result, &diagnostic_store, floating_range.start, .invalid_range_bound, ast.node_span(&tree, floating_range.start))
    floating_end_error :: try expect_error(&result, &diagnostic_store, floating_range.end, .invalid_range_bound, ast.node_span(&tree, floating_range.end))
    try testing.expect(floating_start_error != floating_end_error)
    for (usize(5)..usize(8)) |index| try expect_kind(&result, ast.package_decl(&tree, index), .float)
    try testing.expect_equal(9, code_count(&diagnostic_store, .invalid_range_bound))
    try testing.expect_equal(2, code_count(&diagnostic_store, .unknown_name))
    try testing.expect_equal(0, code_count(&diagnostic_store, .invalid_for_iterable))
    try testing.expect_equal(0, code_count(&diagnostic_store, .cannot_infer_type))
}

range_values_nonrange_iterables_and_capture_modes_have_explicit_errors test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `stored :: 0..3
        `produced proc() int { return 0..3 }
        `consume proc(value int) void {}
        `scalar proc() int { return 2 }
        `main proc() void {
        `    0..3
        `    consume(0..3)
        `    local :: 0..3
        `    for 3 |_| { absent_scalar }
        `    for true |_| {}
        `    for 2.5 |_| {}
        `    for scalar() |_| {}
        `    for stored |_| {}
        `    for 0..3 |@item| { item }
        `    for 0..3 |item, index| { item + index }
        `    for 0..3 |_, _| {}
        `    for 0..3 |@item, _| {}
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    stored :: ast.package_decl(&tree, 0)
    stored_value :: ast.statement_decl(&tree, stored).initializer
    stored_error :: try expect_error(&result, &diagnostic_store, stored_value, .range_value_not_supported, ast.node_span(&tree, stored_value))
    try testing.expect_equal(stored_error, type_of(&result, stored).diagnostic)
    produced_body :: ast.function_decl(&tree, ast.package_decl(&tree, 1)).body
    returned :: ast.return_stmt(&tree, ast.block_statement(&tree, produced_body, 0)).value?
    _ = try expect_error(&result, &diagnostic_store, returned, .range_value_not_supported, ast.node_span(&tree, returned))
    main_body :: ast.function_decl(&tree, ast.package_decl(&tree, 4)).body
    standalone :: ast.statement_expr(&tree, ast.block_statement(&tree, main_body, 0))
    call :: ast.statement_expr(&tree, ast.block_statement(&tree, main_body, 1))
    local_value :: ast.statement_decl(&tree, ast.block_statement(&tree, main_body, 2)).initializer
    values [3]ast.NodeId :: [standalone, ast.call_arg(&tree, call, 0), local_value]
    for values |value| {
        _ = try expect_error(&result, &diagnostic_store, value, .range_value_not_supported, ast.node_span(&tree, value))
    }
    for (usize(3)..usize(7)) |index| {
        statement :: ast.block_statement(&tree, main_body, index)
        loop :: ast.for_stmt(&tree, statement)
        original :: try expect_error(&result, &diagnostic_store, loop.iterable, .invalid_for_iterable, ast.node_span(&tree, loop.iterable))
        try testing.expect_equal(original, type_of(&result, statement).diagnostic)
    }
    stored_loop :: ast.block_statement(&tree, main_body, 7)
    try testing.expect_equal(stored_error, type_of(&result, stored_loop).diagnostic)
    modes [4]diagnostics.Code :: [.range_pointer_capture, .range_index_capture, .range_index_capture, .range_pointer_capture]
    for modes |code, index| {
        statement :: ast.block_statement(&tree, main_body, index + 8)
        _ = try expect_error(&result, &diagnostic_store, statement, code, ast.node_span(&tree, statement))
    }
    indexed :: ast.for_stmt(&tree, ast.block_statement(&tree, main_body, 9))
    try expect_kind(&result, indexed.capture?, .int)
    try expect_kind(&result, indexed.index?, .int)
    try expect_kind(&result, ast.statement_expr(&tree, ast.block_statement(&tree, indexed.body, 0)), .int)
    try testing.expect_equal(5, code_count(&diagnostic_store, .range_value_not_supported))
    try testing.expect_equal(4, code_count(&diagnostic_store, .invalid_for_iterable))
    try testing.expect_equal(2, code_count(&diagnostic_store, .range_pointer_capture))
    try testing.expect_equal(3, code_count(&diagnostic_store, .range_index_capture))
    try testing.expect_equal(1, code_count(&diagnostic_store, .unknown_name))
    try testing.expect_equal(0, code_count(&diagnostic_store, .return_type_mismatch))
    try testing.expect_equal(0, code_count(&diagnostic_store, .type_mismatch))
}

range_captures_are_fixed_readonly_and_assignment_values_do_not_retarget_bounds test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `consume proc(value float) void {}
        `returned proc() float {
        `    for 0..2 |item| { return item }
        `    return 1
        `}
        `main proc() void {
        `    limit := 3
        `    real := 1.5
        `    for 0..limit |item| {
        `        item = 2
        `        if true { item = 1.5 }
        `        while false { item = -"bad" }
        `        real = item
        `        real = limit
        `        consume(item)
        `        copy :: item
        `        consume(copy)
        `    }
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    returned_body :: ast.function_decl(&tree, ast.package_decl(&tree, 1)).body
    returned_loop :: ast.for_stmt(&tree, ast.block_statement(&tree, returned_body, 0))
    returned_value :: ast.return_stmt(&tree, ast.block_statement(&tree, returned_loop.body, 0)).value?
    _ = try expect_error(&result, &diagnostic_store, returned_value, .return_type_mismatch, ast.node_span(&tree, returned_value))
    try expect_kind(&result, returned_loop.capture?, .int)
    main_body :: ast.function_decl(&tree, ast.package_decl(&tree, 2)).body
    limit :: ast.block_statement(&tree, main_body, 0)
    real :: ast.block_statement(&tree, main_body, 1)
    loop_statement :: ast.block_statement(&tree, main_body, 2)
    loop :: ast.for_stmt(&tree, loop_statement)
    try expect_kind(&result, limit, .int)
    try expect_kind(&result, real, .float)
    try expect_kind(&result, loop_statement, .void)
    try expect_kind(&result, loop.iterable, .range)
    try expect_kind(&result, ast.range_expr(&tree, loop.iterable).end, .int)
    try expect_kind(&result, loop.capture?, .int)
    conditional :: ast.if_stmt(&tree, ast.block_statement(&tree, loop.body, 1))
    inner :: ast.while_stmt(&tree, ast.block_statement(&tree, loop.body, 2))
    readonly [3]ast.NodeId :: [
        ast.block_statement(&tree, loop.body, 0),
        ast.block_statement(&tree, conditional.then_block, 0),
        ast.block_statement(&tree, inner.body, 0),
    ]
    for readonly |statement| {
        assignment :: ast.assignment_stmt(&tree, statement)
        _ = try expect_error(&result, &diagnostic_store, statement, .invalid_assignment_target, ast.node_span(&tree, assignment.target))
        try expect_kind(&result, assignment.target, .int)
    }
    dead_value :: ast.assignment_stmt(&tree, readonly[2]).value
    _ = try expect_error(&result, &diagnostic_store, dead_value, .invalid_operand, ast.node_span(&tree, dead_value))
    for (usize(3)..usize(5)) |index| {
        assignment :: ast.assignment_stmt(&tree, ast.block_statement(&tree, loop.body, index))
        _ = try expect_error(&result, &diagnostic_store, assignment.value, .type_mismatch, ast.node_span(&tree, assignment.value))
        try expect_kind(&result, assignment.target, .float)
    }
    for (usize(5)..usize(8)) |index| {
        if (index == 6) continue
        call :: ast.statement_expr(&tree, ast.block_statement(&tree, loop.body, index))
        argument :: ast.call_arg(&tree, call, 0)
        _ = try expect_error(&result, &diagnostic_store, argument, .type_mismatch, ast.node_span(&tree, argument))
    }
    try expect_kind(&result, ast.block_statement(&tree, loop.body, 6), .int)
    try testing.expect_equal(3, code_count(&diagnostic_store, .invalid_assignment_target))
    try testing.expect_equal(4, code_count(&diagnostic_store, .type_mismatch))
    try testing.expect_equal(1, code_count(&diagnostic_store, .return_type_mismatch))
    try testing.expect_equal(1, code_count(&diagnostic_store, .invalid_operand))
    try testing.expect_equal(0, code_count(&diagnostic_store, .invalid_range_bound))
    try testing.expect_equal(0, code_count(&diagnostic_store, .missing_return))
}

range_loop_return_flow_and_controls_are_lexical_and_body_errors_are_isolated test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `missing proc() int { for 0..=0 |_| { return 1 } }
        `bad_body proc() int { for 2..1 |_| { -"bad" } }
        `breaking proc() int { for 0..2 |_| { break } }
        `continuing proc() int { for 2..1 |_| { continue } }
        `closed proc() int {
        `    for 2..1 |_| { -"bad" }
        `    return 7
        `}
        `scopes proc(flag bool) void {
        `    for 0..2 |item| {
        `        if (flag) break else continue
        `        while flag {
        `            if (flag) continue else break
        `            for 0..item |_| { continue }
        `        }
        `        absent
        `    }
        `    while flag { for 0..2 |_| { break } }
        `    break
        `    continue
        `    item
        `}
        `callee proc() void {
        `    break
        `    continue
        `}
        `caller proc() void {
        `    for 0..2 |_| {
        `        callee()
        `        break
        `    }
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    for (usize(0)..usize(4)) |index| {
        function :: ast.package_decl(&tree, index)
        body :: ast.function_decl(&tree, function).body
        try expect_kind(&result, function, .function)
        _ = try expect_fallthrough(&result, &diagnostic_store, function, ast.node_span(&tree, body))
        try expect_kind(&result, ast.block_statement(&tree, body, 0), .void)
    }
    closed_body :: ast.function_decl(&tree, ast.package_decl(&tree, 4)).body
    closed_statement :: ast.block_statement(&tree, closed_body, 0)
    closed_loop :: ast.for_stmt(&tree, closed_statement)
    dead_value :: ast.statement_expr(&tree, ast.block_statement(&tree, closed_loop.body, 0))
    original :: try expect_error(&result, &diagnostic_store, dead_value, .invalid_operand, ast.node_span(&tree, dead_value))
    try testing.expect_equal(original, type_of(&result, closed_body).diagnostic)
    try expect_kind(&result, closed_statement, .void)
    try expect_kind(&result, ast.block_statement(&tree, closed_body, 1), .void)
    scopes_body :: ast.function_decl(&tree, ast.package_decl(&tree, 5)).body
    outer_statement :: ast.block_statement(&tree, scopes_body, 0)
    outer :: ast.for_stmt(&tree, outer_statement)
    conditional :: ast.if_stmt(&tree, ast.block_statement(&tree, outer.body, 0))
    inner_statement :: ast.block_statement(&tree, outer.body, 1)
    inner :: ast.while_stmt(&tree, inner_statement)
    inner_if :: ast.if_stmt(&tree, ast.block_statement(&tree, inner.body, 0))
    nested_statement :: ast.block_statement(&tree, inner.body, 1)
    nested :: ast.for_stmt(&tree, nested_statement)
    controls [5]ast.NodeId :: [
        ast.block_statement(&tree, conditional.then_block, 0),
        ast.block_statement(&tree, conditional.else_block?, 0),
        ast.block_statement(&tree, inner_if.then_block, 0),
        ast.block_statement(&tree, inner_if.else_block?, 0),
        ast.block_statement(&tree, nested.body, 0),
    ]
    for (controls) |statement| try expect_kind(&result, statement, .void)
    try expect_kind(&result, outer_statement, .void)
    try expect_kind(&result, inner_statement, .void)
    try expect_kind(&result, nested_statement, .void)
    absent :: ast.statement_expr(&tree, ast.block_statement(&tree, outer.body, 2))
    try testing.expect_equal(sema.binding(&resolution, absent).data.diagnostic, type_of(&result, absent).diagnostic)
    escaped :: ast.statement_expr(&tree, ast.block_statement(&tree, scopes_body, 4))
    try testing.expect_equal(sema.binding(&resolution, escaped).data.diagnostic, type_of(&result, escaped).diagnostic)
    try testing.expect_equal(4, code_count(&diagnostic_store, .missing_return))
    try testing.expect_equal(2, code_count(&diagnostic_store, .invalid_operand))
    try testing.expect_equal(2, code_count(&diagnostic_store, .unknown_name))
    try testing.expect_equal(2, code_count(&diagnostic_store, .break_outside_loop))
    try testing.expect_equal(2, code_count(&diagnostic_store, .continue_outside_loop))
}

invalid_range_capture_bindings_keep_resolver_diagnostic_ids_without_erasing_headers test {
    strings := strpool.init(mem.c_allocator)
    defer strpool.deinit(&strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `main proc() void {
        `    existing :: 7
        `    for 0..1 |existing| { sibling :: 1 }
        `    for 0..1 |int| { sibling :: 2 }
        `    for 0..1 |item| { item :: 3 }
        `    for 0..1 |item| { copy :: item }
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &strings, &diagnostic_store)
    tree := try parser.parse(mem.c_allocator, scan_state.tokens.items, source, &diagnostic_store)
    defer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &diagnostic_store)
    defer sema.deinit(&resolution)
    previous_count :: diagnostics.count(&diagnostic_store)
    result := try check(mem.c_allocator, &tree, &resolution, &diagnostic_store)
    defer deinit(&result)

    function :: ast.package_decl(&tree, 0)
    body :: ast.function_decl(&tree, function).body
    try expect_kind(&result, function, .function)
    try expect_kind(&result, ast.block_statement(&tree, body, 0), .int)
    for (usize(1)..usize(3)) |index| {
        statement :: ast.block_statement(&tree, body, index)
        loop :: ast.for_stmt(&tree, statement)
        capture :: loop.capture?
        binding :: sema.binding(&resolution, capture)
        try testing.expect_equal(sema.BindingKind.invalid, binding.kind)
        try testing.expect_equal(TypeKind.invalid, type_of(&result, capture).kind)
        try testing.expect_equal(binding.data.diagnostic, type_of(&result, capture).diagnostic)
        try testing.expect_equal(binding.data.diagnostic, type_of(&result, loop.body).diagnostic)
        try expect_kind(&result, statement, .void)
        try expect_kind(&result, loop.iterable, .range)
        try expect_kind(&result, ast.block_statement(&tree, loop.body, 0), .int)
    }
    duplicate_loop :: ast.for_stmt(&tree, ast.block_statement(&tree, body, 3))
    duplicate :: ast.block_statement(&tree, duplicate_loop.body, 0)
    try expect_kind(&result, duplicate_loop.capture?, .int)
    try testing.expect_equal(sema.binding(&resolution, duplicate).data.diagnostic, type_of(&result, duplicate).diagnostic)
    sibling_loop :: ast.for_stmt(&tree, ast.block_statement(&tree, body, 4))
    try expect_kind(&result, sibling_loop.capture?, .int)
    try expect_kind(&result, ast.block_statement(&tree, sibling_loop.body, 0), .int)
    try testing.expect_equal(previous_count, diagnostics.count(&diagnostic_store))
}

@hide:file
ArrayFixture :: struct {
    strings strpool.StringPool
    tree ast.Tree
    resolution sema.Resolution
    diagnostics diagnostics.Store
    result Result
}

@hide:file
array_fixture proc(source []u8) ArrayFixture ! (mem.AllocError | strpool.InternError | diagnostics.CapacityError | lexer.SourceError) {
    strings := strpool.init(mem.c_allocator)
    errdefer strpool.deinit(&strings)
    store := diagnostics.init(mem.c_allocator)
    errdefer diagnostics.deinit(&store)
    scan := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan)
    try lexer.scan(&scan, source, &strings, &store)
    tree := try parser.parse(mem.c_allocator, scan.tokens.items, source, &store)
    errdefer ast.deinit(&tree)
    resolution := try sema.resolve(mem.c_allocator, &tree, &strings, &store)
    errdefer sema.deinit(&resolution)
    result :: try check(mem.c_allocator, &tree, &resolution, &store)
    return ArrayFixture{ strings = strings, tree = tree, resolution = resolution, diagnostics = store, result = result }
}

@hide:file
deinit_array_fixture proc(fixture @mut ArrayFixture) void {
    deinit(&fixture.result)
    sema.deinit(&fixture.resolution)
    ast.deinit(&fixture.tree)
    diagnostics.deinit(&fixture.diagnostics)
    strpool.deinit(&fixture.strings)
}

@hide:file
expect_array proc(result @Result, id ast.NodeId, len usize, mutable bool, element TypeKind) ArrayType ! testing.Error {
    try expect_kind(result, id, .array)
    actual :: array_type(result, type_of(result, id).array_type)
    try testing.expect_equal(len, actual.len)
    try testing.expect_equal(mutable, actual.mutable)
    try testing.expect_equal(element, actual.element.kind)
    return actual
}

fixed_arrays_contextualize_forward_aliases_counts_nested_literals_and_signatures test {
    source ::
        `context [2]f64 :: forwarded
        `forwarded :: seed
        `seed := [1, 2]
        `count :: later * 2 - 1
        `later :: 2
        `nested [_]mut [2]mut i64 := [[1, 2], [3, 4]]
        `empty [_]bool :: []
        `plain :: []
        `copy :: nested
        `index usize :: 0
        `child float :: seed[index]
        `produce proc(value [2]f64) [2]f64 { return value }
        `called :: produce([5, 6])
        `from_result [_]f64 :: called
        `counted [count]i64 :: [1, 2, 3]
    fixture := try array_fixture(source)
    defer deinit_array_fixture(&fixture)
    tree :: &fixture.tree
    result :: &fixture.result
    for (0..usize(3)) |i| _ = try expect_array(result, ast.package_decl(tree, i), 2, false, .float)
    seed :: ast.statement_decl(tree, ast.package_decl(tree, 2)).initializer
    for (0..ast.array_element_count(tree, seed)) |i| try expect_kind(result, ast.array_element(tree, seed, i), .float)
    nested :: ast.package_decl(tree, 5)
    shape :: try expect_array(result, nested, 2, true, .array)
    row :: array_type(result, shape.element.array_type)
    try testing.expect_equal(2, row.len)
    try testing.expect(row.mutable)
    try testing.expect_equal(TypeKind.int, row.element.kind)
    annotation :: ast.statement_decl(tree, nested).type?
    _ = try expect_array(result, annotation, 2, true, .array)
    _ = try expect_array(result, ast.package_decl(tree, 6), 0, false, .bool)
    _ = try expect_array(result, ast.package_decl(tree, 7), 0, false, .int)
    try testing.expect_equal(type_of(result, nested).array_type, type_of(result, ast.package_decl(tree, 8)).array_type)
    indexed :: ast.index_expr(tree, ast.statement_decl(tree, ast.package_decl(tree, 10)).initializer)
    try expect_kind(result, indexed.index, .usize)
    try expect_kind(result, ast.statement_decl(tree, ast.package_decl(tree, 10)).initializer, .float)
    function :: ast.package_decl(tree, 11)
    _ = try expect_array(result, ast.function_param(tree, function, 0), 2, false, .float)
    _ = try expect_array(result, ast.function_decl(tree, function).return_type, 2, false, .float)
    call :: ast.statement_decl(tree, ast.package_decl(tree, 12)).initializer
    argument :: ast.call_arg(tree, call, 0)
    _ = try expect_array(result, argument, 2, false, .float)
    try expect_kind(result, ast.array_element(tree, argument, 0), .float)
    _ = try expect_array(result, ast.package_decl(tree, 13), 2, false, .float)
    _ = try expect_array(result, ast.package_decl(tree, 14), 3, false, .int)
    try testing.expect(array_type_count(result) > 0)
    try testing.expect_equal(0, diagnostics.count(&fixture.diagnostics))
}

nested_array_numeric_context_flows_through_index_children_before_defaults test {
    source ::
        `first float :: later[0][0]
        `later := [[1, 2], [3, 4]]
        `row :: later[0]
        `mixed :: [[1, 2], [3.5, 4]]
        `identity proc(value int) int { return value }
        `another proc(value int) int { return value + 1 }
        `functions :: [identity, another]
    fixture := try array_fixture(source)
    defer deinit_array_fixture(&fixture)
    tree :: &fixture.tree
    result :: &fixture.result
    for usize(1)..usize(4) |i| {
        element_kind TypeKind :: if (i == 2) .float else .array
        type :: try expect_array(result, ast.package_decl(tree, i), 2, false, element_kind)
        if (type.element.kind == .array) try testing.expect_equal(TypeKind.float, array_type(result, type.element.array_type).element.kind)
    }
    matrix :: ast.statement_decl(tree, ast.package_decl(tree, 1)).initializer
    for 0..ast.array_element_count(tree, matrix) |i| {
        row :: ast.array_element(tree, matrix, i)
        for (0..ast.array_element_count(tree, row)) |j| try expect_kind(result, ast.array_element(tree, row, j), .float)
    }
    outer :: ast.statement_decl(tree, ast.package_decl(tree, 0)).initializer
    inner :: ast.index_expr(tree, outer).base
    _ = try expect_array(result, inner, 2, false, .float)
    try expect_kind(result, outer, .float)
    try expect_kind(result, ast.index_expr(tree, outer).index, .usize)
    try expect_kind(result, ast.index_expr(tree, inner).index, .usize)
    _ = try expect_array(result, ast.package_decl(tree, 6), 2, false, .function)
    try testing.expect_equal(0, diagnostics.count(&fixture.diagnostics))
}

fixed_index_errors_are_occurrence_local_and_preserve_sources_and_siblings test {
    source ::
        `fixed i64 :: 0
        `inferred := 0
        `source [2]i64 :: [10, 20]
        `bad :: source[fixed]
        `good :: source[inferred]
        `boolean :: source[true]
        `missing :: source[unknown]
        `tail :: source[1]
    fixture := try array_fixture(source)
    defer deinit_array_fixture(&fixture)
    tree :: &fixture.tree
    result :: &fixture.result
    try expect_kind(result, ast.package_decl(tree, 0), .int)
    try expect_kind(result, ast.package_decl(tree, 1), .usize)
    _ = try expect_array(result, ast.package_decl(tree, 2), 2, false, .int)
    bad_id :: ast.statement_decl(tree, ast.package_decl(tree, 3)).initializer
    bad :: ast.index_expr(tree, bad_id)
    original :: try expect_error(result, &fixture.diagnostics, bad.index, .invalid_index_type, ast.node_span(tree, bad.index))
    try testing.expect_equal(original, type_of(result, bad_id).diagnostic)
    try testing.expect_equal(original, type_of(result, ast.package_decl(tree, 3)).diagnostic)
    _ = try expect_array(result, bad.base, 2, false, .int)
    try expect_kind(result, ast.package_decl(tree, 4), .int)
    boolean :: ast.index_expr(tree, ast.statement_decl(tree, ast.package_decl(tree, 5)).initializer).index
    _ = try expect_error(result, &fixture.diagnostics, boolean, .invalid_index_type, ast.node_span(tree, boolean))
    missing :: ast.index_expr(tree, ast.statement_decl(tree, ast.package_decl(tree, 6)).initializer).index
    try testing.expect_equal(sema.binding(&fixture.resolution, missing).data.diagnostic, type_of(result, missing).diagnostic)
    try expect_kind(result, ast.package_decl(tree, 7), .int)
    try testing.expect_equal(2, code_count(&fixture.diagnostics, .invalid_index_type))
    try testing.expect_equal(1, code_count(&fixture.diagnostics, .unknown_name))
    try testing.expect_equal(3, diagnostics.count(&fixture.diagnostics))
}

array_lengths_require_supported_constexpr_and_finalize_nested_inferred_counts test {
    source ::
        `two :: tail
        `tail :: 2
        `valid [two * 3 - 4]i64 :: [1, 2]
        `zero [3 - 3]i64 :: []
        `nested [_]mut [_]mut i64 := [[1, 2], [3, 4]]
        `negative [-1]i64 :: []
        `fraction [1.5]i64 :: []
        `runtime_count := 2
        `runtime_array [runtime_count]i64 :: [1, 2]
        `count proc() int { return 2 }
        `called [count()]i64 :: [1, 2]
        `a :: b
        `b :: a
        `cycle [a]i64 :: []
        `overflow [18446744073709551615 + 1]i64 :: []
        `wrong [2]i64 :: [1]
        `constraints [2]mut int := [1, 2]
        `floats [0]float :: []
        `voids [0]void :: []
        `missing [absent]i64 :: []
    fixture := try array_fixture(source)
    defer deinit_array_fixture(&fixture)
    tree :: &fixture.tree
    result :: &fixture.result
    _ = try expect_array(result, ast.package_decl(tree, 2), 2, false, .int)
    _ = try expect_array(result, ast.package_decl(tree, 3), 0, false, .int)
    nested :: ast.statement_decl(tree, ast.package_decl(tree, 4))
    shape :: try expect_array(result, nested.type?, 2, true, .array)
    child :: array_type(result, shape.element.array_type)
    try testing.expect_equal(2, child.len)
    try testing.expect(child.mutable)
    _ = try expect_array(result, ast.array_type(tree, nested.type?).element, 2, true, .int)
    invalid_lengths [6]usize :: [5, 6, 8, 10, 13, 14]
    for invalid_lengths |i| {
        annotation :: ast.statement_decl(tree, ast.package_decl(tree, i)).type?
        count :: ast.array_type(tree, annotation).count?
        _ = try expect_error(result, &fixture.diagnostics, annotation, .invalid_array_length, ast.node_span(tree, count))
    }
    wrong :: ast.statement_decl(tree, ast.package_decl(tree, 15)).initializer
    _ = try expect_error(result, &fixture.diagnostics, wrong, .array_length_mismatch, ast.node_span(tree, wrong))
    for usize(16)..usize(19) |i| {
        annotation :: ast.statement_decl(tree, ast.package_decl(tree, i)).type?
        child_id :: ast.array_type(tree, annotation).element
        _ = try expect_error(result, &fixture.diagnostics, annotation, .invalid_array_element_type, ast.node_span(tree, child_id))
    }
    missing :: ast.statement_decl(tree, ast.package_decl(tree, 19)).type?
    count :: ast.array_type(tree, missing).count?
    try testing.expect_equal(sema.binding(&fixture.resolution, count).data.diagnostic, type_of(result, missing).diagnostic)
    try testing.expect_equal(6, code_count(&fixture.diagnostics, .invalid_array_length))
    try testing.expect_equal(1, code_count(&fixture.diagnostics, .array_length_mismatch))
    try testing.expect_equal(3, code_count(&fixture.diagnostics, .invalid_array_element_type))
}

indexed_writes_require_mutable_local_root_and_each_array_level_but_copies_are_values test {
    source ::
        `global [1]mut i64 := [1]
        `main proc(parameter [1]mut i64) void {
        `    mutable [1]mut i64 := [1]
        `    mutable[0] = 2
        `    copied := mutable
        `    copied[0] = 3
        `    inferred := [1]
        `    inferred[0] = 4
        `    inferred = [5]
        `    constant [1]mut i64 :: [1]
        `    constant[0] = 6
        `    parameter[0] = 7
        `    global[0] = 8
        `    outer_readonly [1][1]mut i64 := [[1]]
        `    (outer_readonly[0])[0] = 9
        `    inner_readonly [1]mut [1]i64 := [[1]]
        `    (inner_readonly[0])[0] = 10
        `    both [1]mut [1]mut i64 := [[1]]
        `    (both[0])[0] = 11
        `    both[0] = [12]
        `    mismatch [1]mut i64 := inner_readonly[0]
        `}
    fixture := try array_fixture(source)
    defer deinit_array_fixture(&fixture)
    tree :: &fixture.tree
    result :: &fixture.result
    body :: ast.function_decl(tree, ast.package_decl(tree, 1)).body
    valid [6]usize :: [1, 3, 6, 16, 17, 2]
    for valid |i| {
        id :: ast.block_statement(tree, body, i)
        kind TypeKind :: if (i == 2) .array else .void
        try expect_kind(result, id, kind)
    }
    invalid [6]usize :: [5, 8, 9, 10, 12, 14]
    for invalid |i| {
        id :: ast.block_statement(tree, body, i)
        target :: ast.assignment_stmt(tree, id).target
        _ = try expect_error(result, &fixture.diagnostics, id, .invalid_index_assignment, ast.node_span(tree, target))
        try expect_kind(result, target, .int)
        try expect_kind(result, ast.index_expr(tree, target).index, .usize)
    }
    mismatch :: ast.statement_decl(tree, ast.block_statement(tree, body, 18)).initializer
    _ = try expect_error(result, &fixture.diagnostics, mismatch, .type_mismatch, ast.node_span(tree, mismatch))
    _ = try expect_array(result, ast.block_statement(tree, body, 4), 1, false, .int)
    _ = try expect_array(result, ast.function_param(tree, ast.package_decl(tree, 1), 0), 1, true, .int)
    try testing.expect_equal(6, code_count(&fixture.diagnostics, .invalid_index_assignment))
    try testing.expect_equal(1, code_count(&fixture.diagnostics, .type_mismatch))
}

usize_arithmetic_ranges_and_readonly_captures_keep_the_bound_family test {
    source ::
        `limit usize :: 18446744073709551615
        `arithmetic usize :: (limit - 2) * 1 + 1
        `ordered :: 0 < limit
        `equal :: limit == 18446744073709551615
        `negated :: -limit
        `divided :: limit / 2
        `fixed i64 :: 1
        `mixed :: fixed + limit
        `main proc() void {
        `    source [2]i64 :: [1, 2]
        `    for 0..limit |index| {
        `        source[index]
        `        index = 1
        `    }
        `    for 0..2 |index| { source[index] }
        `    for limit..=limit |_| {}
        `}
    fixture := try array_fixture(source)
    defer deinit_array_fixture(&fixture)
    tree :: &fixture.tree
    result :: &fixture.result
    try expect_kind(result, ast.package_decl(tree, 0), .usize)
    try expect_kind(result, ast.package_decl(tree, 1), .usize)
    try expect_kind(result, ast.package_decl(tree, 2), .bool)
    try expect_kind(result, ast.package_decl(tree, 3), .bool)
    for usize(4)..usize(8) |i| {
        if (i == 6) continue
        value :: ast.statement_decl(tree, ast.package_decl(tree, i)).initializer
        code diagnostics.Code :: if (i == 5) .integer_division else .invalid_operand
        _ = try expect_error(result, &fixture.diagnostics, value, code, ast.node_span(tree, value))
    }
    body :: ast.function_decl(tree, ast.package_decl(tree, 8)).body
    unsigned_loop :: ast.for_stmt(tree, ast.block_statement(tree, body, 1))
    try expect_kind(result, unsigned_loop.capture?, .usize)
    try testing.expect_equal(TypeKind.usize, type_of(result, unsigned_loop.iterable).range_element)
    interval :: ast.range_expr(tree, unsigned_loop.iterable)
    try expect_kind(result, interval.start, .usize)
    try expect_kind(result, interval.end, .usize)
    read :: ast.statement_expr(tree, ast.block_statement(tree, unsigned_loop.body, 0))
    try expect_kind(result, read, .int)
    try expect_kind(result, ast.index_expr(tree, read).index, .usize)
    readonly :: ast.block_statement(tree, unsigned_loop.body, 1)
    target :: ast.assignment_stmt(tree, readonly).target
    _ = try expect_error(result, &fixture.diagnostics, readonly, .invalid_assignment_target, ast.node_span(tree, target))
    try expect_kind(result, target, .usize)
    signed_loop :: ast.for_stmt(tree, ast.block_statement(tree, body, 2))
    try expect_kind(result, signed_loop.capture?, .int)
    signed_read :: ast.statement_expr(tree, ast.block_statement(tree, signed_loop.body, 0))
    bad_index :: ast.index_expr(tree, signed_read).index
    _ = try expect_error(result, &fixture.diagnostics, bad_index, .invalid_index_type, ast.node_span(tree, bad_index))
    try testing.expect_equal(TypeKind.int, type_of(result, signed_loop.iterable).range_element)
    _ = try expect_array(result, ast.block_statement(tree, body, 0), 2, false, .int)
    ignored :: ast.for_stmt(tree, ast.block_statement(tree, body, 3))
    try testing.expect_equal(TypeKind.usize, type_of(result, ignored.iterable).range_element)
    try testing.expect_equal(1, code_count(&fixture.diagnostics, .invalid_index_type))
    try testing.expect_equal(0, code_count(&fixture.diagnostics, .invalid_range_bound))
}

array_assignment_rhs_is_contextual_but_does_not_retarget_established_sources test {
    source ::
        `main proc() void {
        `    target [2]mut f64 := [1, 2]
        `    seed := 3
        `    source [2]i64 :: [4, 5]
        `    target = [seed, 6]
        `    target = source
        `    target = [1]
        `    matrix [1]mut [2]mut i64 := [[1, 2]]
        `    matrix[0] = [7, 8]
        `    matrix[0] = [true, false]
        `    unknown [1]mut i64 := [absent]
        `    unknown[0] = 9
        `    good := 10
        `}
    fixture := try array_fixture(source)
    defer deinit_array_fixture(&fixture)
    tree :: &fixture.tree
    result :: &fixture.result
    body :: ast.function_decl(tree, ast.package_decl(tree, 0)).body
    _ = try expect_array(result, ast.block_statement(tree, body, 0), 2, true, .float)
    try expect_kind(result, ast.block_statement(tree, body, 1), .int)
    _ = try expect_array(result, ast.block_statement(tree, body, 2), 2, false, .int)
    contextual :: ast.assignment_stmt(tree, ast.block_statement(tree, body, 3)).value
    _ = try expect_error(result, &fixture.diagnostics, ast.array_element(tree, contextual, 0), .type_mismatch, ast.node_span(tree, ast.array_element(tree, contextual, 0)))
    try expect_kind(result, ast.array_element(tree, contextual, 1), .float)
    copied :: ast.assignment_stmt(tree, ast.block_statement(tree, body, 4)).value
    _ = try expect_error(result, &fixture.diagnostics, copied, .type_mismatch, ast.node_span(tree, copied))
    wrong_len :: ast.assignment_stmt(tree, ast.block_statement(tree, body, 5)).value
    _ = try expect_error(result, &fixture.diagnostics, wrong_len, .array_length_mismatch, ast.node_span(tree, wrong_len))
    try expect_kind(result, ast.block_statement(tree, body, 7), .void)
    literal :: ast.statement_decl(tree, ast.block_statement(tree, body, 9)).initializer
    missing :: ast.array_element(tree, literal, 0)
    original :: sema.binding(&fixture.resolution, missing).data.diagnostic
    try testing.expect_equal(original, type_of(result, literal).diagnostic)
    try testing.expect_equal(original, type_of(result, ast.block_statement(tree, body, 9)).diagnostic)
    try testing.expect_equal(original, type_of(result, ast.block_statement(tree, body, 10)).diagnostic)
    try expect_kind(result, ast.block_statement(tree, body, 11), .int)
}

array_signature_identity_includes_recursive_counts_and_mutability test {
    source ::
        `accept proc(value [1]mut i64) [1]mut i64 { return value }
        `different_count proc(value [2]mut i64) [1]mut i64 { return [1] }
        `different_mutability proc(value [1]i64) [1]mut i64 { return [1] }
        `functions :: [accept, different_count, different_mutability]
        `wrong_return proc() [1]mut i64 {
        `    value [1]i64 :: [1]
        `    return value
        `}
        `take proc(value [2]i64) void {}
        `caller proc() void {
        `    take([1])
        `    take([true, false])
        `}
    fixture := try array_fixture(source)
    defer deinit_array_fixture(&fixture)
    tree :: &fixture.tree
    result :: &fixture.result
    functions :: ast.statement_decl(tree, ast.package_decl(tree, 3)).initializer
    for usize(1)..usize(3) |i| {
        value :: ast.array_element(tree, functions, i)
        _ = try expect_error(result, &fixture.diagnostics, value, .type_mismatch, ast.node_span(tree, value))
        try expect_kind(result, ast.package_decl(tree, i), .function)
    }
    wrong :: ast.package_decl(tree, 4)
    wrong_body :: ast.function_decl(tree, wrong).body
    value :: ast.return_stmt(tree, ast.block_statement(tree, wrong_body, 1)).value?
    _ = try expect_error(result, &fixture.diagnostics, value, .return_type_mismatch, ast.node_span(tree, value))
    _ = try expect_array(result, ast.block_statement(tree, wrong_body, 0), 1, false, .int)
    try expect_kind(result, wrong, .function)
    caller :: ast.function_decl(tree, ast.package_decl(tree, 6)).body
    call :: ast.statement_expr(tree, ast.block_statement(tree, caller, 0))
    argument :: ast.call_arg(tree, call, 0)
    _ = try expect_error(result, &fixture.diagnostics, argument, .array_length_mismatch, ast.node_span(tree, argument))
    second :: ast.statement_expr(tree, ast.block_statement(tree, caller, 1))
    literal :: ast.call_arg(tree, second, 0)
    for 0..ast.array_element_count(tree, literal) |i| {
        child :: ast.array_element(tree, literal, i)
        _ = try expect_error(result, &fixture.diagnostics, child, .type_mismatch, ast.node_span(tree, child))
    }
    try expect_kind(result, ast.package_decl(tree, 5), .function)
}

inferred_counts_follow_forward_fixed_aliases_empty_shapes_and_reject_local_counts test {
    source ::
        `forward [_]i64 :: later
        `later [_]i64 :: [1, 2]
        `zero [_]mut bool := []
        `nested [_][_]bool :: [[], []]
        `unsigned usize :: 5
        `main proc() void {
        `    local_count :: 2
        `    unsupported [local_count]i64 :: [1, 2]
        `    values [2]i64 :: [1, 2]
        `    for 0..(unsigned + 1) |index| { values[index] }
        `}
    fixture := try array_fixture(source)
    defer deinit_array_fixture(&fixture)
    tree :: &fixture.tree
    result :: &fixture.result
    for 0..usize(2) |i| {
        declaration :: ast.statement_decl(tree, ast.package_decl(tree, i))
        _ = try expect_array(result, declaration.type?, 2, false, .int)
        _ = try expect_array(result, ast.package_decl(tree, i), 2, false, .int)
    }
    _ = try expect_array(result, ast.package_decl(tree, 2), 0, true, .bool)
    shape :: try expect_array(result, ast.package_decl(tree, 3), 2, false, .array)
    child :: array_type(result, shape.element.array_type)
    try testing.expect_equal(0, child.len)
    try testing.expect_equal(TypeKind.bool, child.element.kind)
    body :: ast.function_decl(tree, ast.package_decl(tree, 5)).body
    unsupported :: ast.statement_decl(tree, ast.block_statement(tree, body, 1)).type?
    count :: ast.array_type(tree, unsupported).count?
    _ = try expect_error(result, &fixture.diagnostics, unsupported, .invalid_array_length, ast.node_span(tree, count))
    try expect_kind(result, ast.block_statement(tree, body, 0), .int)
    loop :: ast.for_stmt(tree, ast.block_statement(tree, body, 3))
    try expect_kind(result, loop.capture?, .usize)
    try testing.expect_equal(TypeKind.usize, type_of(result, loop.iterable).range_element)
    read :: ast.statement_expr(tree, ast.block_statement(tree, loop.body, 0))
    try expect_kind(result, read, .int)
    try testing.expect_equal(1, code_count(&fixture.diagnostics, .invalid_array_length))
    try testing.expect_equal(1, diagnostics.count(&fixture.diagnostics))
}