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
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 {
    strpool.strings = strpool.init(mem.c_allocator)
    defer strpool.deinit(&strpool.strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `forward float :: -alias * 2 + seed
        `alias :: 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 / (alias + 1)
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &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, &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 {
    strpool.strings = strpool.init(mem.c_allocator)
    defer strpool.deinit(&strpool.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, &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, &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 {
    strpool.strings = strpool.init(mem.c_allocator)
    defer strpool.deinit(&strpool.strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `alias :: alpha
        `alpha proc(a, b int) void {
        `    (alias)(a, b)
        `    beta(a + b, seed)
        `}
        `beta proc(total int, amount float) void {
        `    alpha(total, 2)
        `}
        `seed := 3
        `main proc() void {
        `    beta(1, 2)
        `    (alias)(3, 4)
        `}
    scan_state := lexer.init(mem.c_allocator)
    defer lexer.deinit(&scan_state)
    try lexer.scan(&scan_state, source, &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, &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 {
    strpool.strings = strpool.init(mem.c_allocator)
    defer strpool.deinit(&strpool.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, &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, &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 {
    strpool.strings = strpool.init(mem.c_allocator)
    defer strpool.deinit(&strpool.strings)
    diagnostic_store := diagnostics.init(mem.c_allocator)
    defer diagnostics.deinit(&diagnostic_store)
    source ::
        `answer :: alias()
        `alias :: 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, &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, &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_error(&result, &diagnostic_store, view.body, .missing_return, ast.node_span(&tree, view.body))
    }
    broken :: ast.package_decl(&tree, 4)
    try expect_kind(&result, broken, .function)
    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
    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 {
    strpool.strings = strpool.init(mem.c_allocator)
    defer strpool.deinit(&strpool.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, &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, &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 {
    strpool.strings = strpool.init(mem.c_allocator)
    defer strpool.deinit(&strpool.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, &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, &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 {
    strpool.strings = strpool.init(mem.c_allocator)
    defer strpool.deinit(&strpool.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, &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, &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 {
    strpool.strings = strpool.init(mem.c_allocator)
    defer strpool.deinit(&strpool.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, &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, &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 {
    strpool.strings = strpool.init(mem.c_allocator)
    defer strpool.deinit(&strpool.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 }
        `unreachable 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, &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, &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_body :: ast.function_decl(&tree, ast.package_decl(&tree, 6)).body
    _ = try expect_error(&result, &diagnostic_store, missing_body, .missing_return, 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))
}