diff --git a/README.md b/README.md
index 3443a9d..f0c39ae 100644
--- a/README.md
+++ b/README.md
@@ -10,4 +10,8 @@ bro build
 
 The parser supports arithmetic expressions with nested parenthesized groups, such as `a + (b - c) * 2 / 3`. Groups control precedence without adding AST nodes; inner expression spans exclude the grouping parentheses.
 
-Function calls are postfix expressions: `f()`, `f(a, b)`, and `factory()(x)`. Calls bind tighter than unary and binary arithmetic and can appear in initializers or as expression statements inside function bodies. Argument lists allow a trailing comma; newlines remain statement boundaries. Name resolution and argument/type checking belong to semantic analysis.
+Function calls are postfix expressions: `f()`, `f(a, b)`, and `factory()(x)`. Calls bind tighter than unary and binary arithmetic and can appear in initializers or as expression statements inside function bodies. Argument lists allow a trailing comma; newlines remain statement boundaries. Argument/type checking belongs to semantic analysis and is not yet implemented.
+
+Name resolution (`@source/sema`) runs after parsing. It predeclares package names and function-body locals, allowing forward references and mutually recursive functions. Parameters and locals share a function scope; signatures resolve names in the enclosing package scope. Shadowing is forbidden, including reuse of builtin type names (`int`, `float`, `string`, `void`); sibling function scopes may independently reuse names.
+
+`sema.resolve` returns an owned binding table indexed by AST `NodeId`, without modifying the AST. `sema.binding` identifies a declaration, builtin type, or invalid binding carrying its diagnostic ID; nodes with no binding return `.none`. Release the result with `sema.deinit`. Unknown names and duplicate declarations add source-spanned diagnostics; invalid syntax retains its existing diagnostic identity. Same-scope duplicates retain the first declaration for recovery, while forbidden inner declarations invalidate that name's uses rather than silently binding them to an outer declaration. Type checking and read-before-initialization checks remain separate, unimplemented stages.
diff --git a/source/ast/ast.hon b/source/ast/ast.hon
index a0efcfd..e33f64e 100644
--- a/source/ast/ast.hon
+++ b/source/ast/ast.hon
@@ -345,6 +345,10 @@ add_invalid_decl proc(builder @mut Builder, span Span, diagnostic DiagnosticId)
     }, span)
 }
 
+node_count proc(tree @Tree) usize {
+    return tree.storage.nodes.items.len
+}
+
 package_decl_count proc(tree @Tree) usize {
     root :: get_node(&tree.storage, tree.root)
     debug.assert(root.kind == .package)
diff --git a/source/diagnostics/diagnostics.hon b/source/diagnostics/diagnostics.hon
index ae9fd85..dfcfc60 100644
--- a/source/diagnostics/diagnostics.hon
+++ b/source/diagnostics/diagnostics.hon
@@ -14,6 +14,8 @@ Code :: enum {
     float_must_end_with_digit,
     unterminated_string,
     unexpected_token,
+    duplicate_name,
+    unknown_name,
 }
 
 Diagnostic :: struct {
diff --git a/source/main.hon b/source/main.hon
index 7222c9a..12ab112 100644
--- a/source/main.hon
+++ b/source/main.hon
@@ -6,6 +6,7 @@ import "@source/strpool"
 import "@source/lexer"
 import "@source/ast"
 import "@source/parser"
+import "@source/sema"
 
 ast_renderer :: import "@source/ast/renderer"
 
@@ -20,6 +21,7 @@ test import "@source/lexer"
 test import "@source/ast"
 test import "@source/ast/renderer"
 test import "@source/parser"
+test import "@source/sema"
 
 program ::
     `# literals
@@ -30,11 +32,13 @@ program ::
     `a := 1 + 2 * 3
     `b :: -3 / 2 + 1
     `
-    `empty proc() void {}
-    `grouped proc(a, b T, c U) void {
-    `    value int :: 1
+    `grouped proc(left, right int, extra float) void {
+    `    value int :: later + left
+    `    later int :: right
     `    empty()
+    `    grouped(value, later, extra)
     `}
+    `empty proc() void {}
 
 main proc() void! {
     strpool.STRINGS = strpool.init(mem.c_allocator)
@@ -55,6 +59,9 @@ main proc() void! {
     )
     defer ast.deinit(&tree)
 
+    resolution := try sema.resolve(&tree, &diagnostic_store, mem.c_allocator)
+    defer sema.deinit(&resolution)
+
     renderer := ast_renderer.init(mem.c_allocator)
     defer ast_renderer.deinit(&renderer)
     try ast_renderer.render(&renderer, &tree)
diff --git a/source/sema/resolve.hon b/source/sema/resolve.hon
new file mode 100644
index 0000000..9a68723
--- /dev/null
+++ b/source/sema/resolve.hon
@@ -0,0 +1,247 @@
+import "@std/debug"
+import "@std/mem"
+import "@std/hashmap"
+import "@std/strmap"
+
+import "@source/ast"
+import "@source/diagnostics"
+
+BuiltinType :: enum { int, float, string, void }
+
+@hide:file
+builtins strmap.StaticStringMap(BuiltinType) :: strmap.init([
+    { "int", .int },
+    { "float", .float },
+    { "string", .string },
+    { "void", .void },
+])
+
+BindingKind :: enum { none, declaration, builtin, invalid }
+
+BindingData :: union {
+    declaration ast.NodeId
+    builtin BuiltinType
+    diagnostic diagnostics.DiagnosticId
+}
+
+Binding :: struct {
+    kind BindingKind = .none
+    data BindingData = BindingData{ diagnostic = diagnostics.NO_DIAGNOSTIC }
+}
+
+@hide:file
+Storage :: struct {
+    bindings []mut Binding
+    allocator mem.Allocator
+}
+
+Resolution :: struct { storage Storage }
+
+@hide:file
+Scope :: struct {
+    names hashmap.StringHashMap(Binding)
+    parent ?@Scope
+}
+
+@hide:file
+State :: struct {
+    tree @ast.Tree
+    diagnostics @mut diagnostics.Store
+    bindings []mut Binding
+    allocator mem.Allocator
+}
+
+resolve proc(
+    tree @ast.Tree,
+    diagnostic_store @mut diagnostics.Store,
+    allocator mem.Allocator,
+) Resolution ! (mem.AllocError | diagnostics.CapacityError) {
+    bindings :: try mem.alloc(Binding, allocator, ast.node_count(tree))
+    errdefer mem.free(allocator, bindings)
+    for (0..bindings.len) |i| bindings[i] = Binding{}
+
+    state := State{
+        tree = tree,
+        diagnostics = diagnostic_store,
+        bindings = bindings,
+        allocator = allocator,
+    }
+
+    package_scope := Scope{ names = hashmap.init(allocator), parent = null }
+    defer hashmap.deinit(&package_scope.names)
+    for (0..ast.package_decl_count(tree)) |i| {
+        id :: ast.package_decl(tree, i)
+        match ast.decl_kind(tree, id) {
+            .statement: try predeclare(&state, &package_scope, id, ast.statement_decl(tree, id).name)
+            .function: try predeclare(&state, &package_scope, id, ast.function_decl(tree, id).name)
+            .invalid: {}
+        }
+    }
+
+    for (0..ast.package_decl_count(tree)) |i| {
+        id :: ast.package_decl(tree, i)
+        match ast.decl_kind(tree, id) {
+            .statement: try resolve_statement_decl(&state, &package_scope, id)
+            .function: try resolve_function(&state, &package_scope, id)
+            .invalid: resolve_invalid(&state, id)
+        }
+    }
+
+    return Resolution{ storage = Storage{ bindings = bindings, allocator = allocator } }
+}
+
+deinit proc(resolution @mut Resolution) void {
+    mem.free(resolution.storage.allocator, resolution.storage.bindings)
+}
+
+binding proc(resolution @Resolution, id ast.NodeId) Binding {
+    debug.assert(usize(id) < resolution.storage.bindings.len)
+    return resolution.storage.bindings[usize(id)]
+}
+
+@hide:file
+lookup proc(scope ?@Scope, name []u8) ?Binding {
+    if scope |current| {
+        if hashmap.get(&current.names, name) |found| return found
+        return lookup(current.parent, name)
+    }
+    if strmap.get(&builtins, name) |type| {
+        return Binding{ kind = .builtin, data = BindingData{ builtin = type } }
+    }
+    return null
+}
+
+@hide:file
+put_name proc(scope @mut Scope, name []u8, value Binding) void ! mem.AllocError {
+    hashmap.put(&scope.names, name, value) catch |err| {
+        match err {
+            .key_exists: unreachable
+            else: return err
+        }
+    }
+}
+
+@hide:file
+predeclare proc(
+    state @mut State,
+    scope @mut Scope,
+    id ast.NodeId,
+    name_span ast.Span,
+) void ! (mem.AllocError | diagnostics.CapacityError) {
+    name :: ast.source_text(state.tree, name_span)
+    if hashmap.get(&scope.names, name) |_| {
+        diagnostic :: try diagnostics.add(state.diagnostics, .duplicate_name, name_span)
+        state.bindings[usize(id)] = Binding{
+            kind = .invalid,
+            data = BindingData{ diagnostic = diagnostic },
+        }
+        return
+    }
+
+    value := Binding{ kind = .declaration, data = BindingData{ declaration = id } }
+    if lookup(scope.parent, name) |_| {
+        diagnostic :: try diagnostics.add(state.diagnostics, .duplicate_name, name_span)
+        # Poison the inner name rather than silently binding uses to its ancestor.
+        value = Binding{ kind = .invalid, data = BindingData{ diagnostic = diagnostic } }
+    }
+    try put_name(scope, name, value)
+    state.bindings[usize(id)] = value
+}
+
+@hide:file
+resolve_function proc(
+    state @mut State,
+    package_scope @Scope,
+    id ast.NodeId,
+) void ! (mem.AllocError | diagnostics.CapacityError) {
+    tree :: state.tree
+    function :: ast.function_decl(tree, id)
+    # Signatures cannot see parameters or body-local declarations.
+    try resolve_expr(state, package_scope, function.return_type)
+    for (0..ast.function_param_count(tree, id)) |i| {
+        parameter :: ast.function_param(tree, id, i)
+        try resolve_expr(state, package_scope, ast.param(tree, parameter).type)
+    }
+
+    scope := Scope{ names = hashmap.init(state.allocator), parent = package_scope }
+    defer hashmap.deinit(&scope.names)
+    for (0..ast.function_param_count(tree, id)) |i| {
+        parameter :: ast.function_param(tree, id, i)
+        try predeclare(state, &scope, parameter, ast.param(tree, parameter).name)
+    }
+    for (0..ast.block_statement_count(tree, function.body)) |i| {
+        statement :: ast.block_statement(tree, function.body, i)
+        if ast.stmt_kind(tree, statement) == .declaration {
+            try predeclare(state, &scope, statement, ast.statement_decl(tree, statement).name)
+        }
+    }
+
+    for (0..ast.block_statement_count(tree, function.body)) |i| {
+        statement :: ast.block_statement(tree, function.body, i)
+        match ast.stmt_kind(tree, statement) {
+            .declaration: try resolve_statement_decl(state, &scope, statement)
+            .expression: try resolve_expr(state, &scope, ast.statement_expr(tree, statement))
+            .invalid: resolve_invalid(state, statement)
+        }
+    }
+}
+
+@hide:file
+resolve_statement_decl proc(
+    state @mut State,
+    scope @Scope,
+    id ast.NodeId,
+) void ! (mem.AllocError | diagnostics.CapacityError) {
+    declaration :: ast.statement_decl(state.tree, id)
+    if (declaration.type) |type| try resolve_expr(state, scope, type)
+    try resolve_expr(state, scope, declaration.initializer)
+}
+
+@hide:file
+resolve_invalid proc(state @mut State, id ast.NodeId) void {
+    if (state.bindings[usize(id)].kind != .none) return
+    state.bindings[usize(id)] = Binding{
+        kind = .invalid,
+        data = BindingData{ diagnostic = ast.invalid(state.tree, id).diagnostic },
+    }
+}
+
+@hide:file
+resolve_expr proc(
+    state @mut State,
+    scope @Scope,
+    id ast.NodeId,
+) void ! (mem.AllocError | diagnostics.CapacityError) {
+    # Grouped parameters share their type node, including any diagnostic it owns.
+    if (state.bindings[usize(id)].kind != .none) return
+    tree :: state.tree
+    match ast.expr_kind(tree, id) {
+        .literal_int, .literal_float, .literal_string: {}
+        .identifier: {
+            span :: ast.node_span(tree, id)
+            name :: ast.source_text(tree, span)
+            if lookup(scope, name) |found| {
+                state.bindings[usize(id)] = found
+            } else {
+                diagnostic :: try diagnostics.add(state.diagnostics, .unknown_name, span)
+                state.bindings[usize(id)] = Binding{
+                    kind = .invalid,
+                    data = BindingData{ diagnostic = diagnostic },
+                }
+            }
+        }
+        .unary: try resolve_expr(state, scope, ast.unary_expr(tree, id).operand)
+        .binary: {
+            expression :: ast.binary_expr(tree, id)
+            try resolve_expr(state, scope, expression.left)
+            try resolve_expr(state, scope, expression.right)
+        }
+        .call: {
+            try resolve_expr(state, scope, ast.call_expr(tree, id).callee)
+            for (0..ast.call_arg_count(tree, id)) |i| {
+                try resolve_expr(state, scope, ast.call_arg(tree, id, i))
+            }
+        }
+        .invalid: resolve_invalid(state, id)
+    }
+}
diff --git a/source/sema/resolve.test.hon b/source/sema/resolve.test.hon
new file mode 100644
index 0000000..5564d5e
--- /dev/null
+++ b/source/sema/resolve.test.hon
@@ -0,0 +1,253 @@
+import "@std/mem"
+import "@std/testing"
+
+import "@source/diagnostics"
+import "@source/strpool"
+import "@source/lexer"
+import "@source/parser"
+import "@source/ast"
+
+resolves_forward_references_recursion_and_builtin_signatures 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 ::
+        `first :: later
+        `alpha proc(p int, q float, s string) void {
+        `    before :: -after * p + beta(after)
+        `    after :: later
+        `}
+        `beta proc(p int) void {
+        `    after :: p
+        `    alpha(after, 1.0, "x")
+        `}
+        `later int :: 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(scan_state.tokens.items, source, &diagnostic_store, mem.c_allocator)
+    defer ast.deinit(&tree)
+    resolution := try resolve(&tree, &diagnostic_store, mem.c_allocator)
+    defer deinit(&resolution)
+
+    first :: ast.package_decl(&tree, 0)
+    alpha :: ast.package_decl(&tree, 1)
+    beta :: ast.package_decl(&tree, 2)
+    later :: ast.package_decl(&tree, 3)
+    alpha_view :: ast.function_decl(&tree, alpha)
+    beta_view :: ast.function_decl(&tree, beta)
+    before :: ast.block_statement(&tree, alpha_view.body, 0)
+    after :: ast.block_statement(&tree, alpha_view.body, 1)
+    p :: ast.function_param(&tree, alpha, 0)
+    q :: ast.function_param(&tree, alpha, 1)
+    s :: ast.function_param(&tree, alpha, 2)
+    sibling_p :: ast.function_param(&tree, beta, 0)
+    sibling_after :: ast.block_statement(&tree, beta_view.body, 0)
+    first_ref :: ast.statement_decl(&tree, first).initializer
+    after_ref :: ast.statement_decl(&tree, after).initializer
+    references [2]ast.NodeId :: [first_ref, after_ref]
+    for references |id| {
+        try testing.expect_equal(BindingKind.declaration, binding(&resolution, id).kind)
+        try testing.expect_equal(later, binding(&resolution, id).data.declaration)
+    }
+    add :: ast.binary_expr(&tree, ast.statement_decl(&tree, before).initializer)
+    multiply :: ast.binary_expr(&tree, add.left)
+    forward_ref :: ast.unary_expr(&tree, multiply.left).operand
+    try testing.expect_equal(BindingKind.declaration, binding(&resolution, forward_ref).kind)
+    try testing.expect_equal(after, binding(&resolution, forward_ref).data.declaration)
+    try testing.expect_equal(BindingKind.declaration, binding(&resolution, multiply.right).kind)
+    try testing.expect_equal(p, binding(&resolution, multiply.right).data.declaration)
+    beta_ref :: ast.call_expr(&tree, add.right).callee
+    try testing.expect_equal(BindingKind.declaration, binding(&resolution, beta_ref).kind)
+    try testing.expect_equal(beta, binding(&resolution, beta_ref).data.declaration)
+    argument :: ast.call_arg(&tree, add.right, 0)
+    try testing.expect_equal(BindingKind.declaration, binding(&resolution, argument).kind)
+    try testing.expect_equal(after, binding(&resolution, argument).data.declaration)
+    recursive_call :: ast.statement_expr(&tree, ast.block_statement(&tree, beta_view.body, 1))
+    alpha_ref :: ast.call_expr(&tree, recursive_call).callee
+    try testing.expect_equal(BindingKind.declaration, binding(&resolution, alpha_ref).kind)
+    try testing.expect_equal(alpha, binding(&resolution, alpha_ref).data.declaration)
+    sibling_ref :: ast.call_arg(&tree, recursive_call, 0)
+    try testing.expect_equal(BindingKind.declaration, binding(&resolution, sibling_ref).kind)
+    try testing.expect_equal(sibling_after, binding(&resolution, sibling_ref).data.declaration)
+    sibling_param_ref :: ast.statement_decl(&tree, sibling_after).initializer
+    try testing.expect_equal(BindingKind.declaration, binding(&resolution, sibling_param_ref).kind)
+    try testing.expect_equal(sibling_p, binding(&resolution, sibling_param_ref).data.declaration)
+    parameter_types [2]ast.NodeId :: [ast.param(&tree, p).type, ast.param(&tree, sibling_p).type]
+    for parameter_types |id| {
+        try testing.expect_equal(BindingKind.builtin, binding(&resolution, id).kind)
+        try testing.expect_equal(BuiltinType.int, binding(&resolution, id).data.builtin)
+    }
+    if (ast.statement_decl(&tree, later).type) |type| {
+        try testing.expect_equal(BindingKind.builtin, binding(&resolution, type).kind)
+        try testing.expect_equal(BuiltinType.int, binding(&resolution, type).data.builtin)
+    } else {
+        return .expectation_failed
+    }
+    try testing.expect_equal(BindingKind.builtin, binding(&resolution, ast.param(&tree, q).type).kind)
+    try testing.expect_equal(BuiltinType.float, binding(&resolution, ast.param(&tree, q).type).data.builtin)
+    try testing.expect_equal(BindingKind.builtin, binding(&resolution, ast.param(&tree, s).type).kind)
+    try testing.expect_equal(BuiltinType.string, binding(&resolution, ast.param(&tree, s).type).data.builtin)
+    return_types [2]ast.NodeId :: [alpha_view.return_type, beta_view.return_type]
+    for return_types |id| {
+        try testing.expect_equal(BindingKind.builtin, binding(&resolution, id).kind)
+        try testing.expect_equal(BuiltinType.void, binding(&resolution, id).data.builtin)
+    }
+    try testing.expect_equal(0, diagnostics.count(&diagnostic_store))
+}
+
+rejects_shadowing_and_duplicates_without_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 ::
+        `collide proc(outer int, p int, p int) outer {
+        `    outer :: missing
+        `    outer :: 1
+        `    p :: 1
+        `    int :: 1
+        `    pkg :: 1
+        `    outer
+        `    p
+        `    int
+        `    pkg
+        `}
+        `outer :: 1
+        `pkg :: 1
+        `same :: 1
+        `same :: same
+    scan_state := lexer.init(mem.c_allocator)
+    defer lexer.deinit(&scan_state)
+    try lexer.scan(&scan_state, source, &diagnostic_store)
+    tree := try parser.parse(scan_state.tokens.items, source, &diagnostic_store, mem.c_allocator)
+    defer ast.deinit(&tree)
+    try testing.expect_equal(0, diagnostics.count(&diagnostic_store))
+    resolution := try resolve(&tree, &diagnostic_store, mem.c_allocator)
+    defer deinit(&resolution)
+
+    function :: ast.package_decl(&tree, 0)
+    view :: ast.function_decl(&tree, function)
+    outer :: ast.package_decl(&tree, 1)
+    first_same :: ast.package_decl(&tree, 3)
+    second_same :: ast.package_decl(&tree, 4)
+    outer_param :: ast.function_param(&tree, function, 0)
+    p :: ast.function_param(&tree, function, 1)
+    duplicate_p :: ast.function_param(&tree, function, 2)
+    first_outer :: ast.block_statement(&tree, view.body, 0)
+    second_outer :: ast.block_statement(&tree, view.body, 1)
+    local_p :: ast.block_statement(&tree, view.body, 2)
+    local_int :: ast.block_statement(&tree, view.body, 3)
+    local_pkg :: ast.block_statement(&tree, view.body, 4)
+    rejected [8]ast.NodeId :: [outer_param, duplicate_p, first_outer, second_outer, local_p, local_int, local_pkg, second_same]
+    for rejected |id| {
+        invalid_binding :: binding(&resolution, id)
+        try testing.expect_equal(BindingKind.invalid, invalid_binding.kind)
+        if (diagnostics.get(&diagnostic_store, invalid_binding.data.diagnostic)) |diagnostic| {
+            try testing.expect_equal(diagnostics.Code.duplicate_name, diagnostic.code)
+            name :: if (id == outer_param or id == duplicate_p) ast.param(&tree, id).name else ast.statement_decl(&tree, id).name
+            try testing.expect_equal(name.start, diagnostic.span.start)
+            try testing.expect_equal(name.end, diagnostic.span.end)
+        } else {
+            return .expectation_failed
+        }
+    }
+    try testing.expect(binding(&resolution, first_outer).data.diagnostic != binding(&resolution, second_outer).data.diagnostic)
+    try testing.expect(binding(&resolution, outer_param).data.diagnostic != binding(&resolution, first_outer).data.diagnostic)
+    try testing.expect(binding(&resolution, duplicate_p).data.diagnostic != binding(&resolution, local_p).data.diagnostic)
+    outer_ref :: ast.statement_expr(&tree, ast.block_statement(&tree, view.body, 5))
+    try testing.expect_equal(BindingKind.invalid, binding(&resolution, outer_ref).kind)
+    try testing.expect_equal(binding(&resolution, outer_param).data.diagnostic, binding(&resolution, outer_ref).data.diagnostic)
+    p_ref :: ast.statement_expr(&tree, ast.block_statement(&tree, view.body, 6))
+    try testing.expect_equal(BindingKind.declaration, binding(&resolution, p_ref).kind)
+    try testing.expect_equal(p, binding(&resolution, p_ref).data.declaration)
+    int_ref :: ast.statement_expr(&tree, ast.block_statement(&tree, view.body, 7))
+    try testing.expect_equal(BindingKind.invalid, binding(&resolution, int_ref).kind)
+    try testing.expect_equal(binding(&resolution, local_int).data.diagnostic, binding(&resolution, int_ref).data.diagnostic)
+    pkg_ref :: ast.statement_expr(&tree, ast.block_statement(&tree, view.body, 8))
+    try testing.expect_equal(BindingKind.invalid, binding(&resolution, pkg_ref).kind)
+    try testing.expect_equal(binding(&resolution, local_pkg).data.diagnostic, binding(&resolution, pkg_ref).data.diagnostic)
+    try testing.expect_equal(BindingKind.declaration, binding(&resolution, view.return_type).kind)
+    try testing.expect_equal(outer, binding(&resolution, view.return_type).data.declaration)
+    parameter_type :: ast.param(&tree, outer_param).type
+    try testing.expect_equal(BindingKind.builtin, binding(&resolution, parameter_type).kind)
+    try testing.expect_equal(BuiltinType.int, binding(&resolution, parameter_type).data.builtin)
+    same_ref :: ast.statement_decl(&tree, second_same).initializer
+    try testing.expect_equal(BindingKind.declaration, binding(&resolution, same_ref).kind)
+    try testing.expect_equal(first_same, binding(&resolution, same_ref).data.declaration)
+    missing :: ast.statement_decl(&tree, first_outer).initializer
+    try testing.expect_equal(BindingKind.invalid, binding(&resolution, missing).kind)
+    if (diagnostics.get(&diagnostic_store, binding(&resolution, missing).data.diagnostic)) |diagnostic| {
+        try testing.expect_equal(diagnostics.Code.unknown_name, diagnostic.code)
+        try testing.expect_equal(ast.node_span(&tree, missing).start, diagnostic.span.start)
+        try testing.expect_equal(ast.node_span(&tree, missing).end, diagnostic.span.end)
+    } else {
+        return .expectation_failed
+    }
+    try testing.expect_equal(9, diagnostics.count(&diagnostic_store))
+}
+
+preserves_syntax_diagnostics_and_resolves_shared_unknown_types_once 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 + absent
+        `    valid :: later
+        `    later :: 1
+        `    discarded(1 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(scan_state.tokens.items, source, &diagnostic_store, mem.c_allocator)
+    defer ast.deinit(&tree)
+    syntax_count :: diagnostics.count(&diagnostic_store)
+    invalid_decl :: ast.package_decl(&tree, 0)
+    try testing.expect_equal(ast.DeclKind.invalid, ast.decl_kind(&tree, invalid_decl))
+    function :: ast.package_decl(&tree, 1)
+    view :: ast.function_decl(&tree, function)
+    empty :: ast.statement_decl(&tree, ast.block_statement(&tree, view.body, 0)).initializer
+    try testing.expect_equal(ast.ExprKind.invalid, ast.expr_kind(&tree, empty))
+    invalid_statement :: ast.block_statement(&tree, view.body, 4)
+    try testing.expect_equal(ast.StmtKind.invalid, ast.stmt_kind(&tree, invalid_statement))
+    resolution := try resolve(&tree, &diagnostic_store, mem.c_allocator)
+    defer deinit(&resolution)
+
+    invalid_nodes [3]ast.NodeId :: [invalid_decl, empty, invalid_statement]
+    for invalid_nodes |id| {
+        invalid_view :: ast.invalid(&tree, id)
+        invalid_binding :: binding(&resolution, id)
+        try testing.expect_equal(BindingKind.invalid, invalid_binding.kind)
+        try testing.expect_equal(invalid_view.diagnostic, invalid_binding.data.diagnostic)
+    }
+    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(binding(&resolution, shared_type).data.diagnostic, binding(&resolution, ast.param(&tree, b).type).data.diagnostic)
+    bad :: ast.binary_expr(&tree, ast.statement_decl(&tree, ast.block_statement(&tree, view.body, 1)).initializer)
+    unknown_nodes [3]ast.NodeId :: [shared_type, bad.left, bad.right]
+    for unknown_nodes |id| {
+        invalid_binding :: binding(&resolution, id)
+        try testing.expect_equal(BindingKind.invalid, invalid_binding.kind)
+        if (diagnostics.get(&diagnostic_store, invalid_binding.data.diagnostic)) |diagnostic| {
+            try testing.expect_equal(diagnostics.Code.unknown_name, diagnostic.code)
+            try testing.expect_equal(ast.node_span(&tree, id).start, diagnostic.span.start)
+            try testing.expect_equal(ast.node_span(&tree, id).end, diagnostic.span.end)
+        } else {
+            return .expectation_failed
+        }
+    }
+    try testing.expect(binding(&resolution, bad.left).data.diagnostic != binding(&resolution, bad.right).data.diagnostic)
+    valid :: ast.block_statement(&tree, view.body, 2)
+    later :: ast.block_statement(&tree, view.body, 3)
+    valid_ref :: ast.statement_decl(&tree, valid).initializer
+    try testing.expect_equal(BindingKind.declaration, binding(&resolution, valid_ref).kind)
+    try testing.expect_equal(later, binding(&resolution, valid_ref).data.declaration)
+    try testing.expect_equal(syntax_count + 3, diagnostics.count(&diagnostic_store))
+}