@@ -13,6 +13,7 @@ supertypes:
     - binary_expr
     - unary_expr
     - call_expr
+    - macro_call_expr
     - member_access_expr
     - super_expr
     - function_expr
@@ -171,6 +172,13 @@ named:
     callee: expr
     argument*: argument
 
+  # A macro call expression, such as `#expect(x == y)` in Swift or
+  # `assert!(x == y)` in Rust.
+  macro_call_expr:
+    macro_name_node: identifier
+    type_argument*: expr
+    argument*: argument
+
   argument:
     modifier*: modifier
     name_node?: identifier

@@ -712,6 +712,31 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
             =>
             (argument name_node: (identifier #{lbl})? value: {val})
         ),
+        // An additional labeled trailing closure, such as the `c: { ... }` in
+        // `foo { 42 } c: { ... }`, is turned into an argument to the function.
+        rule!(
+            (multipleTrailingClosureElement label: @@label closure: @closure)
+            =>
+            (argument name_node: (identifier #{label}) value: {closure})
+        ),
+        rule!(
+            (macroExpansionExpr
+                macroName: @@name
+                genericArgumentClause: (genericArgumentClause arguments: (genericArgument argument: @type_args)*)?
+                arguments: _* @args
+                trailingClosure: _? @trailing
+                additionalTrailingClosures: _* @additional)
+            =>
+            macro_call_expr {
+                let mut arguments = args;
+                arguments.extend(trailing.into_iter().map(|trailing| tree!((argument value: {trailing}))));
+                arguments.extend(additional);
+                tree!((macro_call_expr
+                    macro_name_node: (identifier #{name})
+                    type_argument: {type_args}
+                    argument: {arguments}))
+            }
+        ),
         // Member access (`list.append`). The `declName` is itself a
         // `declReferenceExpr`; pull its `baseName` out as the member identifier.
         // A leading-dot access (`.foo`) has no explicit base — the base is an
@@ -1196,10 +1221,6 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
                 }
             }
         ),
-        // Selector expression: `#selector(inner)` -- not yet supported
-        // (swift-syntax represents `#selector`/`#keyPath` and other macro
-        // expansions uniformly as a `macroExpansionExpr`).
-        rule!((macroExpansionExpr) => (unsupported_node)),
         // A nominal type's `inheritanceClause` (`: Base, Proto`) becomes a list
         // of `base_type`s, one per inherited type. Each declaration keyword
         // gets its own rule; the bodies are identical but for the keyword.

@@ -0,0 +1,164 @@
+#expect(value == 42)
+
+#custom<Int>(value) {
+  value
+} completion: {
+  value
+}
+
+#Preview {
+  let previewValue = 42
+  previewValue
+}
+
+---
+
+sourceFile
+  endOfFileToken: endOfFile
+  statements:
+    codeBlockItem
+      item:
+        macroExpansionExpr
+          leftParen: (
+          rightParen: )
+          arguments:
+            labeledExpr
+              expression:
+                infixOperatorExpr
+                  operator:
+                    binaryOperatorExpr
+                      operator: binaryOperator "=="
+                  leftOperand:
+                    declReferenceExpr
+                      baseName: identifier "value"
+                  rightOperand:
+                    integerLiteralExpr
+                      literal: integerLiteral "42"
+          additionalTrailingClosures:
+          macroName: identifier "expect"
+          pound: #
+    codeBlockItem
+      item:
+        macroExpansionExpr
+          leftParen: (
+          rightParen: )
+          arguments:
+            labeledExpr
+              expression:
+                declReferenceExpr
+                  baseName: identifier "value"
+          additionalTrailingClosures:
+            multipleTrailingClosureElement
+              colon: :
+              label: identifier "completion"
+              closure:
+                closureExpr
+                  leftBrace: {
+                  rightBrace: }
+                  statements:
+                    codeBlockItem
+                      item:
+                        declReferenceExpr
+                          baseName: identifier "value"
+          trailingClosure:
+            closureExpr
+              leftBrace: {
+              rightBrace: }
+              statements:
+                codeBlockItem
+                  item:
+                    declReferenceExpr
+                      baseName: identifier "value"
+          genericArgumentClause:
+            genericArgumentClause
+              arguments:
+                genericArgument
+                  argument:
+                    identifierType
+                      name: identifier "Int"
+              leftAngle: <
+              rightAngle: >
+          macroName: identifier "custom"
+          pound: #
+    codeBlockItem
+      item:
+        macroExpansionExpr
+          arguments:
+          additionalTrailingClosures:
+          trailingClosure:
+            closureExpr
+              leftBrace: {
+              rightBrace: }
+              statements:
+                codeBlockItem
+                  item:
+                    variableDecl
+                      attributes:
+                      modifiers:
+                      bindingSpecifier: let
+                      bindings:
+                        patternBinding
+                          initializer:
+                            initializerClause
+                              equal: =
+                              value:
+                                integerLiteralExpr
+                                  literal: integerLiteral "42"
+                          pattern:
+                            identifierPattern
+                              identifier: identifier "previewValue"
+                codeBlockItem
+                  item:
+                    declReferenceExpr
+                      baseName: identifier "previewValue"
+          macroName: identifier "Preview"
+          pound: #
+
+---
+
+top_level source="⟨body⟩"
+  body:
+    block source="⟨stmt⟩\n\n⟨stmt⟩\n\n⟨stmt⟩"
+      stmt:
+        macro_call_expr source="#⟨macro_name_node⟩(⟨argument⟩)"
+          macro_name_node: identifier "expect" source="expect"
+          argument:
+            argument source="⟨value⟩"
+              value:
+                binary_expr source="⟨left⟩ ⟨operator⟩ ⟨right⟩"
+                  left: identifier "value" source="value"
+                  operator: infix_operator "==" source="=="
+                  right: int_literal "42" source="42"
+        macro_call_expr source="#⟨macro_name_node⟩<⟨type_argument⟩>(⟨argument⟩) ⟨argument⟩ ⟨argument⟩"
+          macro_name_node: identifier "custom" source="custom"
+          type_argument: identifier "Int" source="Int"
+          argument:
+            argument source="⟨value⟩"
+              value: identifier "value" source="value"
+            argument source="⟨value⟩"
+              value:
+                function_expr source="{\n  ⟨body⟩\n}"
+                  body:
+                    block source="⟨stmt⟩"
+                      stmt: identifier "value" source="value"
+            argument source="⟨name_node⟩: ⟨value⟩"
+              name_node: identifier "completion" source="completion"
+              value:
+                function_expr source="{\n  ⟨body⟩\n}"
+                  body:
+                    block source="⟨stmt⟩"
+                      stmt: identifier "value" source="value"
+        macro_call_expr source="#⟨macro_name_node⟩ ⟨argument⟩"
+          macro_name_node: identifier "Preview" source="Preview"
+          argument:
+            argument source="⟨value⟩"
+              value:
+                function_expr source="{\n  ⟨body⟩\n}"
+                  body:
+                    block source="⟨stmt⟩\n  ⟨stmt⟩"
+                      stmt:
+                        variable_declaration source="⟨modifier⟩ ⟨pattern⟩ = ⟨value⟩"
+                          modifier: modifier "let" source="let"
+                          pattern: identifier "previewValue" source="previewValue"
+                          value: int_literal "42" source="42"
+                        identifier "previewValue" source="previewValue"
@@ -0,0 +1,12 @@
+#expect(value == 42)
+
+#custom<Int>(value) {
+  value
+} completion: {
+  value
+}
+
+#Preview {
+  let previewValue = 42
+  previewValue
+}
@@ -35,4 +35,6 @@ top_level source="⟨body⟩"
         variable_declaration source="⟨modifier⟩ ⟨pattern⟩ = ⟨value⟩"
           modifier: modifier "let" source="let"
           pattern: identifier "currentLine" source="currentLine"
-          value: unsupported_node "#line" source="#line"
+          value:
+            macro_call_expr source="#⟨macro_name_node⟩"
+              macro_name_node: identifier "line" source="line"
@@ -956,6 +956,34 @@
     }
   }
 
+  /** A class representing `macro_call_expr` nodes. */
+  class MacroCallExpr extends @unified_macro_call_expr, F::Expr {
+    /** Gets the name of the primary QL class for this element. */
+    final override string getAPrimaryQlClass() { result = "MacroCallExpr" }
+
+    /** Gets the node corresponding to the field `argument`. */
+    final F::Argument getArgument(int i) { unified_macro_call_expr_argument(this, i, result) }
+
+    /** Gets the node corresponding to the field `argument`. */
+    final F::Argument getAnArgument() { result = this.getArgument(_) }
+
+    /** Gets the node corresponding to the field `macro_name_node`. */
+    final F::Identifier getMacroNameNode() { unified_macro_call_expr_def(this, result) }
+
+    /** Gets the node corresponding to the field `type_argument`. */
+    final F::Expr getTypeArgument(int i) { unified_macro_call_expr_type_argument(this, i, result) }
+
+    /** Gets the node corresponding to the field `type_argument`. */
+    final F::Expr getATypeArgument() { result = this.getTypeArgument(_) }
+
+    /** Gets a field or child node of this node. */
+    final override F::AstNode getAFieldOrChild() {
+      unified_macro_call_expr_argument(this, _, result) or
+      unified_macro_call_expr_def(this, result) or
+      unified_macro_call_expr_type_argument(this, _, result)
+    }
+  }
+
   /** A class representing `map_literal` nodes. */
   class MapLiteral extends @unified_map_literal, F::Expr {
     /** Gets the name of the primary QL class for this element. */
@@ -1717,6 +1745,12 @@
       or
       result = node.(LabeledStmt).getStmt() and i = -1 and name = "getStmt"
       or
+      result = node.(MacroCallExpr).getArgument(i) and name = "getArgument"
+      or
+      result = node.(MacroCallExpr).getMacroNameNode() and i = -1 and name = "getMacroNameNode"
+      or
+      result = node.(MacroCallExpr).getTypeArgument(i) and name = "getTypeArgument"
+      or
       result = node.(MapLiteral).getElement(i) and name = "getElement"
       or
       result = node.(MemberAccessExpr).getBase() and i = -1 and name = "getBase"
@@ -1938,6 +1972,8 @@
 
   final class LabeledStmt = F::LabeledStmt;
 
+  final class MacroCallExpr = F::MacroCallExpr;
+
   final class MapLiteral = F::MapLiteral;
 
   final class Member = F::Member;

@@ -440,7 +440,7 @@ unified_equality_type_constraint_def(
   int right: @unified_expr ref
 );
 
-@unified_expr = @unified_array_literal | @unified_binary_expr | @unified_block | @unified_break_expr | @unified_bulk_importing_pattern | @unified_call_expr | @unified_conditional_pattern | @unified_continue_expr | @unified_expr_pattern | @unified_function_expr | @unified_generic_type_expr | @unified_if_expr | @unified_key_value_pair | @unified_map_literal | @unified_member_access_expr | @unified_named_pattern | @unified_or_pattern | @unified_pattern_guard_expr | @unified_return_expr | @unified_string_interpolation_expr | @unified_switch_expr | @unified_throw_expr | @unified_token_boolean_literal | @unified_token_builtin_expr | @unified_token_empty_expr | @unified_token_float_literal | @unified_token_identifier | @unified_token_ignore_pattern | @unified_token_inferred_type_expr | @unified_token_int_literal | @unified_token_regex_literal | @unified_token_string_literal | @unified_token_super_expr | @unified_token_unhandled_node | @unified_token_unsupported_node | @unified_try_expr | @unified_tuple_expr | @unified_type_cast_expr | @unified_type_test_expr | @unified_unary_expr | @unified_unresolved_operator_sequence
+@unified_expr = @unified_array_literal | @unified_binary_expr | @unified_block | @unified_break_expr | @unified_bulk_importing_pattern | @unified_call_expr | @unified_conditional_pattern | @unified_continue_expr | @unified_expr_pattern | @unified_function_expr | @unified_generic_type_expr | @unified_if_expr | @unified_key_value_pair | @unified_macro_call_expr | @unified_map_literal | @unified_member_access_expr | @unified_named_pattern | @unified_or_pattern | @unified_pattern_guard_expr | @unified_return_expr | @unified_string_interpolation_expr | @unified_switch_expr | @unified_throw_expr | @unified_token_boolean_literal | @unified_token_builtin_expr | @unified_token_empty_expr | @unified_token_float_literal | @unified_token_identifier | @unified_token_ignore_pattern | @unified_token_inferred_type_expr | @unified_token_int_literal | @unified_token_regex_literal | @unified_token_string_literal | @unified_token_super_expr | @unified_token_unhandled_node | @unified_token_unsupported_node | @unified_try_expr | @unified_tuple_expr | @unified_type_cast_expr | @unified_type_test_expr | @unified_unary_expr | @unified_unresolved_operator_sequence
 
 @unified_expr_or_operator = @unified_expr | @unified_token_infix_operator
 
@@ -631,6 +631,25 @@ unified_labeled_stmt_def(
   int stmt: @unified_stmt ref
 );
 
+#keyset[unified_macro_call_expr, index]
+unified_macro_call_expr_argument(
+  int unified_macro_call_expr: @unified_macro_call_expr ref,
+  int index: int ref,
+  unique int argument: @unified_argument ref
+);
+
+#keyset[unified_macro_call_expr, index]
+unified_macro_call_expr_type_argument(
+  int unified_macro_call_expr: @unified_macro_call_expr ref,
+  int index: int ref,
+  unique int type_argument: @unified_expr ref
+);
+
+unified_macro_call_expr_def(
+  unique int id: @unified_macro_call_expr,
+  int macro_name_node: @unified_token_identifier ref
+);
+
 #keyset[unified_map_literal, index]
 unified_map_literal_element(
   int unified_map_literal: @unified_map_literal ref,
@@ -1006,7 +1025,7 @@ unified_trivia_tokeninfo(
   string value: string ref
 );
 
-@unified_ast_node = @unified_accessor_declaration | @unified_argument | @unified_array_literal | @unified_associated_type_declaration | @unified_base_type | @unified_binary_expr | @unified_block | @unified_bound_type_constraint | @unified_break_expr | @unified_bulk_importing_pattern | @unified_call_expr | @unified_catch_clause | @unified_class_like_declaration | @unified_conditional_pattern | @unified_constructor_declaration | @unified_continue_expr | @unified_defer_stmt | @unified_destructor_declaration | @unified_do_while_stmt | @unified_equality_type_constraint | @unified_expr_pattern | @unified_for_each_stmt | @unified_function_declaration | @unified_function_expr | @unified_generic_type_expr | @unified_guard_if_stmt | @unified_if_expr | @unified_import_declaration | @unified_initializer_declaration | @unified_key_value_pair | @unified_labeled_stmt | @unified_map_literal | @unified_member_access_expr | @unified_named_pattern | @unified_operator_syntax_declaration | @unified_or_pattern | @unified_parameter | @unified_pattern_guard_expr | @unified_return_expr | @unified_string_interpolation_expr | @unified_switch_case | @unified_switch_expr | @unified_throw_expr | @unified_token | @unified_top_level | @unified_trivia_token | @unified_try_expr | @unified_tuple_expr | @unified_type_alias_declaration | @unified_type_cast_expr | @unified_type_parameter | @unified_type_test_expr | @unified_unary_expr | @unified_unresolved_operator_sequence | @unified_variable_declaration | @unified_while_stmt
+@unified_ast_node = @unified_accessor_declaration | @unified_argument | @unified_array_literal | @unified_associated_type_declaration | @unified_base_type | @unified_binary_expr | @unified_block | @unified_bound_type_constraint | @unified_break_expr | @unified_bulk_importing_pattern | @unified_call_expr | @unified_catch_clause | @unified_class_like_declaration | @unified_conditional_pattern | @unified_constructor_declaration | @unified_continue_expr | @unified_defer_stmt | @unified_destructor_declaration | @unified_do_while_stmt | @unified_equality_type_constraint | @unified_expr_pattern | @unified_for_each_stmt | @unified_function_declaration | @unified_function_expr | @unified_generic_type_expr | @unified_guard_if_stmt | @unified_if_expr | @unified_import_declaration | @unified_initializer_declaration | @unified_key_value_pair | @unified_labeled_stmt | @unified_macro_call_expr | @unified_map_literal | @unified_member_access_expr | @unified_named_pattern | @unified_operator_syntax_declaration | @unified_or_pattern | @unified_parameter | @unified_pattern_guard_expr | @unified_return_expr | @unified_string_interpolation_expr | @unified_switch_case | @unified_switch_expr | @unified_throw_expr | @unified_token | @unified_top_level | @unified_trivia_token | @unified_try_expr | @unified_tuple_expr | @unified_type_alias_declaration | @unified_type_cast_expr | @unified_type_parameter | @unified_type_test_expr | @unified_unary_expr | @unified_unresolved_operator_sequence | @unified_variable_declaration | @unified_while_stmt
 
 unified_ast_node_location(
   unique int node: @unified_ast_node ref,