Unified: Extract Swift conditional compilation blocks

Extract conditional compilation blocks as if expressions. Members can now be nested inside conditional compilation blocks. Rename `member` to `direct_member` as this is now usually the wrong thing to access. A new predicate on the QL side finds all members, both direct and indirect ones through conditional compilation blocks.
paldepind · Nov 3, 2026 · Nov 3, 2026 · Nov 3, 2026 · Nov 3, 2026 · Nov 3, 2026
commit fe0d3be191e49319d23bea1136226bb0978edd27
@@ -68,6 +68,8 @@ supertypes:
     - do_while_stmt
     - defer_stmt
     - labeled_stmt
+    - associated_type_declaration
+    - initializer_declaration
   callable:
     subtypes:
       - top_level
@@ -93,6 +95,7 @@ supertypes:
       - class_like_declaration
       - type_alias_declaration
       - associated_type_declaration
+      - if_expr # For conditional compilation
       - unsupported_node
       - unhandled_node
     fields:
@@ -261,7 +264,10 @@ named:
   block:
     stmt*: stmt
 
+  # An if expression or a conditional compilation directive (which we view as a
+  # compile-time evaluated if expression).
   if_expr:
+    modifier*: modifier
     condition: expr
     then?: expr
     else?: expr
@@ -499,7 +505,7 @@ named:
     type_parameter*: type_parameter
     type_constraint*: type_constraint
     base_type*: base_type
-    member*: member
+    direct_member*: member
 
   # One of the base types of a class declaration.
   #

@@ -38,6 +38,9 @@ struct SwiftContext {
     /// True while translating a pattern. Optional chaining in this context is
     /// represented as an `Optional.some` call rather than being unwrapped.
     in_pattern: bool,
+    /// When iterating over the clauses of a conditional compilation block, this
+    /// holds the tail of the clauses that have already been translated.
+    conditional_compilation_tail: Option<yeast::OutputId>,
 }
 
 impl SwiftContext {
@@ -64,11 +67,29 @@ fn implicit_parameterless_initializer(
     ctx: &mut yeast::build::BuildCtx<'_, SwiftContext>,
     members: &[yeast::OutputId],
 ) -> Option<yeast::OutputId> {
-    let has_explicit_initializer = members.iter().any(|member| {
-        ctx.output
-            .get_node(*member)
-            .is_some_and(|node| node.kind_name() == "constructor_declaration")
-    });
+    // Search for an initializer while recursing into nodes for conditional
+    // compilation blocks.
+    fn find_initializer(ast: &yeast::OutputAst, id: yeast::OutputId) -> Option<yeast::OutputId> {
+        let node = ast.get_node(id)?;
+        match node.kind_name() {
+            "constructor_declaration" => Some(id),
+            name => {
+                let fields: &[&str] = match name {
+                    "if_expr" => &["then", "else"], // look into conditional compilation
+                    "block" => &["stmt"],           // look into blocks in branches
+                    _ => &[],
+                };
+                fields.iter().find_map(|field| {
+                    node.field_children(ast.field_id_for_name(field)?)
+                        .iter()
+                        .find_map(|child| find_initializer(ast, *child))
+                })
+            }
+        }
+    }
+    let has_explicit_initializer = members
+        .iter()
+        .any(|member| find_initializer(ctx.output, *member).is_some());
     (!has_explicit_initializer).then(|| {
         tree!((constructor_declaration
             modifier: (modifier "generated")
@@ -529,7 +550,7 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
                     modifier: [(modifier "chained_declaration") if { ctx.is_chained }]
                     modifier: (modifier "enum_case")
                     name_node: (identifier #{name})
-                    member: {constructor}))
+                    direct_member: {constructor}))
             }
         ),
         rule!(
@@ -872,6 +893,53 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
             =>
             (parameter pattern: (identifier #{name}))
         ),
+        // ---- Conditioal compilation blocks ----
+        // Conditional compilation blocks (`#if … #elseif … #else … #endif`) are
+        // represented with a `ifConfigDecl` node for the entire block and an
+        // `ifConfigClause` for each branch. We translate them into nested
+        // `if_expr` nodes.
+
+        // When a conditional compilation block contains a switch case it
+        // appears within a `switch` -- we do not support this yet.
+        rule!(
+            (ifConfigDecl clauses: (ifConfigClause elements: (switchCase)))
+            =>
+            (unsupported_node)
+        ),
+        // A conditional compilation block is translated into `if_expr` nodes
+        // with branches occurring nested within the else branch.
+        rule!(
+            (ifConfigDecl clauses: _* @@clauses) @@declaration
+            =>
+            expr {
+                ctx.conditional_compilation_tail = None;
+                for clause in clauses.into_iter().rev() {
+                    ctx.conditional_compilation_tail = ctx.translate(clause)?.into_iter().next();
+                }
+                let result = ctx.conditional_compilation_tail.ok_or("conditional compilation has no clauses")?;
+                ctx.set_node_source_range(result, ctx.source_range(declaration))
+            }
+        ),
+        // A single clause is mapped to an if expression with the tail of
+        // already processed clauses (stored in `conditional_compilation_tail`)
+        // inserted into the else branch.
+        rule!(
+            (ifConfigClause condition: @condition elements: _* @items)
+            =>
+            (if_expr
+                // Mark this `if_expr` as coming from conditional compilation.
+                modifier: (modifier "conditional_compilation")
+                condition: {condition}
+                then: (block stmt: {items})
+                else: {ctx.conditional_compilation_tail})
+        ),
+        // A conditional compilation clause without a condition (a final `#else`
+        // block).
+        rule!(
+            (ifConfigClause elements: _* @items)
+            =>
+            (block stmt: {items})
+        ),
         // ---- Control flow ----
         // An `if`/`else` expression. Conditions are joined via `and_chain`; the
         // then-body and optional else-body (another block, or an `ifExpr` for an
@@ -1333,8 +1401,8 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
                     type_constraint: {parameter_constraints}
                     type_constraint: {declaration_constraints}
                     base_type: {bases.into_iter().map(|ty| tree!((base_type type: {ty})))}
-                    member: {members}
-                    member: {implicit_initializer}))
+                    direct_member: {members}
+                    direct_member: {implicit_initializer}))
             }
         ),
         // Enum class declaration: same as a regular class but with an enum body.
@@ -1358,7 +1426,7 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
                 type_constraint: {parameter_constraints}
                 type_constraint: {declaration_constraints}
                 base_type: {bases.into_iter().map(|ty| tree!((base_type type: {ty})))}
-                member: {members})
+                direct_member: {members})
         ),
         // A `struct` declaration, including an implicit parameter-less `init`
         // when no explicit initializer is present.
@@ -1384,8 +1452,8 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
                     type_constraint: {parameter_constraints}
                     type_constraint: {declaration_constraints}
                     base_type: {bases.into_iter().map(|ty| tree!((base_type type: {ty})))}
-                    member: {members}
-                    member: {implicit_initializer}))
+                    direct_member: {members}
+                    direct_member: {implicit_initializer}))
             }
         ),
         // Protocol declaration
@@ -1406,7 +1474,7 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
                 type_parameter: {params}
                 type_constraint: {declaration_constraints}
                 base_type: {bases.into_iter().map(|ty| tree!((base_type type: {ty})))}
-                member: {members})
+                direct_member: {members})
         ),
         // An `extension Foo.Bar { … }` is likewise a `class_like_declaration`.
         rule!(
@@ -1422,7 +1490,7 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
                 modifier: {mods}
                 extension_target: {extendedType}
                 base_type: {bases.into_iter().map(|ty| tree!((base_type type: {ty})))}
-                member: {members})
+                direct_member: {members})
         ),
         // A member of a type declaration unwraps to the contained declaration.
         rule!((memberBlockItem decl: _* @d) => member* { d }),
@@ -1504,7 +1572,6 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
         rule!((copyExpr) => (unsupported_node)),
         rule!((discardStmt) => (unsupported_node)),
         rule!((fallThroughStmt) => (unsupported_node)),
-        rule!((ifConfigDecl) => (unsupported_node)),
         rule!((implicitlyUnwrappedOptionalType) => (unsupported_node)),
         rule!((inlineArrayType) => (unsupported_node)),
         rule!((keyPathExpr) => (unsupported_node)),

@@ -106,6 +106,11 @@ top_level source="⟨body⟩"
         variable_declaration source="⟨modifier⟩\n⟨modifier⟩ ⟨pattern⟩ = ⟨value⟩"
           modifier:
             modifier "let" source="let"
-            unsupported_node "#if DEBUG\n    @available(*, deprecated)\n#endif" source="#if DEBUG\n    @available(*, deprecated)\n#endif" <-- ERROR: The field variable_declaration.modifier should contain modifier, but got unsupported_node
+            if_expr source="#if ⟨condition⟩\n    ⟨then⟩\n#endif" <-- ERROR: The field variable_declaration.modifier should contain modifier, but got if_expr
+              modifier: modifier "conditional_compilation" source=""
+              condition: identifier "DEBUG" source="DEBUG"
+              then:
+                block source="⟨stmt⟩"
+                  stmt: modifier "@available(*, deprecated)" source="@available(*, deprecated)" <-- ERROR: The field block.stmt should contain stmt, but got modifier
           pattern: identifier "x" source="x"
           value: int_literal "1" source="1"
@@ -78,12 +78,23 @@ top_level source="⟨body⟩"
   body:
     block source="⟨stmt⟩"
       stmt:
-        class_like_declaration source="⟨modifier⟩ ⟨name_node⟩ {\n    ⟨member⟩\n}"
+        class_like_declaration source="⟨modifier⟩ ⟨name_node⟩ {\n    ⟨direct_member⟩\n}"
           modifier: modifier "class" source="class"
           name_node: identifier "C" source="C"
-          member:
-            unsupported_node "#if DEBUG\n        init(x: Int) {}\n        deinit {}\n    #endif" source="#if DEBUG\n        init(x: Int) {}\n        deinit {}\n    #endif"
-            constructor_declaration source=""
-              modifier: modifier "generated" source=""
-              name_node: identifier "init" source=""
-              body: block source=""
+          direct_member:
+            if_expr source="#if ⟨condition⟩\n        ⟨then⟩\n    #endif"
+              modifier: modifier "conditional_compilation" source=""
+              condition: identifier "DEBUG" source="DEBUG"
+              then:
+                block source="⟨stmt⟩\n        ⟨stmt⟩"
+                  stmt:
+                    constructor_declaration source="⟨name_node⟩(⟨parameter⟩) ⟨body⟩"
+                      name_node: identifier "init" source="init"
+                      parameter:
+                        parameter source="⟨external_name_node⟩⟨pattern⟩: ⟨type⟩"
+                          external_name_node: identifier "x" source="x"
+                          type: identifier "Int" source="Int"
+                          pattern: identifier "x" source="x"
+                      body: block "{}" source="{}"
+                    destructor_declaration source="deinit ⟨body⟩"
+                      body: block "{}" source="{}"
@@ -273,17 +273,76 @@ top_level source="⟨body⟩"
   body:
     block source="⟨stmt⟩\n\n⟨stmt⟩\n\n⟨stmt⟩"
       stmt:
-        unsupported_node "#if DEBUG\n    let first = 1\n    let second = 2\n    #if EXTRA\n        func f() {}\n    #elseif OTHER\n    #else\n        let third = 3\n    #endif\n#else\n#endif" source="#if DEBUG\n    let first = 1\n    let second = 2\n    #if EXTRA\n        func f() {}\n    #elseif OTHER\n    #else\n        let third = 3\n    #endif\n#else\n#endif"
-        class_like_declaration source="⟨modifier⟩ ⟨name_node⟩ {\n    ⟨member⟩\n}"
+        if_expr source="#if ⟨condition⟩\n    ⟨then⟩\n⟨else⟩\n#endif"
+          modifier: modifier "conditional_compilation" source=""
+          condition: identifier "DEBUG" source="DEBUG"
+          then:
+            block source="⟨stmt⟩\n    ⟨stmt⟩\n    ⟨stmt⟩"
+              stmt:
+                variable_declaration source="⟨modifier⟩ ⟨pattern⟩ = ⟨value⟩"
+                  modifier: modifier "let" source="let"
+                  pattern: identifier "first" source="first"
+                  value: int_literal "1" source="1"
+                variable_declaration source="⟨modifier⟩ ⟨pattern⟩ = ⟨value⟩"
+                  modifier: modifier "let" source="let"
+                  pattern: identifier "second" source="second"
+                  value: int_literal "2" source="2"
+                if_expr source="#if ⟨condition⟩\n        ⟨then⟩\n    ⟨else⟩\n    #endif"
+                  modifier: modifier "conditional_compilation" source=""
+                  condition: identifier "EXTRA" source="EXTRA"
+                  then:
+                    block source="⟨stmt⟩"
+                      stmt:
+                        function_declaration source="func ⟨name_node⟩() ⟨body⟩"
+                          name_node: identifier "f" source="f"
+                          body: block "{}" source="{}"
+                  else:
+                    if_expr source="#elseif ⟨condition⟩\n    ⟨else⟩"
+                      modifier: modifier "conditional_compilation" source=""
+                      condition: identifier "OTHER" source="OTHER"
+                      then: block source=""
+                      else:
+                        block source="#else\n        ⟨stmt⟩"
+                          stmt:
+                            variable_declaration source="⟨modifier⟩ ⟨pattern⟩ = ⟨value⟩"
+                              modifier: modifier "let" source="let"
+                              pattern: identifier "third" source="third"
+                              value: int_literal "3" source="3"
+          else: block "#else" source="#else"
+        class_like_declaration source="⟨modifier⟩ ⟨name_node⟩ {\n    ⟨direct_member⟩\n}"
           modifier: modifier "protocol" source="protocol"
           name_node: identifier "P" source="P"
-          member: unsupported_node "#if DEBUG\n        associatedtype T\n    #endif" source="#if DEBUG\n        associatedtype T\n    #endif"
+          direct_member:
+            if_expr source="#if ⟨condition⟩\n        ⟨then⟩\n    #endif"
+              modifier: modifier "conditional_compilation" source=""
+              condition: identifier "DEBUG" source="DEBUG"
+              then:
+                block source="⟨stmt⟩"
+                  stmt:
+                    associated_type_declaration source="associatedtype ⟨name_node⟩"
+                      name_node: identifier "T" source="T"
         function_declaration source="func ⟨name_node⟩() ⟨body⟩"
           name_node: identifier "use" source="use"
           body:
             block source="{\n    ⟨stmt⟩\n    ⟨stmt⟩\n}"
               stmt:
-                unsupported_node "#if DEBUG\n        let value = 1\n    #else\n        let value = 2\n    #endif" source="#if DEBUG\n        let value = 1\n    #else\n        let value = 2\n    #endif"
+                if_expr source="#if ⟨condition⟩\n        ⟨then⟩\n    ⟨else⟩\n    #endif"
+                  modifier: modifier "conditional_compilation" source=""
+                  condition: identifier "DEBUG" source="DEBUG"
+                  then:
+                    block source="⟨stmt⟩"
+                      stmt:
+                        variable_declaration source="⟨modifier⟩ ⟨pattern⟩ = ⟨value⟩"
+                          modifier: modifier "let" source="let"
+                          pattern: identifier "value" source="value"
+                          value: int_literal "1" source="1"
+                  else:
+                    block source="#else\n        ⟨stmt⟩"
+                      stmt:
+                        variable_declaration source="⟨modifier⟩ ⟨pattern⟩ = ⟨value⟩"
+                          modifier: modifier "let" source="let"
+                          pattern: identifier "value" source="value"
+                          value: int_literal "2" source="2"
                 if_expr source="if ⟨condition⟩ ⟨then⟩"
                   condition: boolean_literal "true" source="true"
                   then:

@@ -122,12 +122,42 @@ top_level source="⟨body⟩"
   body:
     block source="⟨stmt⟩"
       stmt:
-        class_like_declaration source="⟨modifier⟩ ⟨name_node⟩ {\n    ⟨member⟩\n}"
+        class_like_declaration source="⟨modifier⟩ ⟨name_node⟩ {\n    ⟨direct_member⟩\n}"
           modifier: modifier "class" source="class"
           name_node: identifier "C" source="C"
-          member:
-            unsupported_node "#if DEBUG\n        init(x: Int) {}\n    #elseif RELEASE\n        init(x: String) {}\n    #else\n        init() {}\n    #endif" source="#if DEBUG\n        init(x: Int) {}\n    #elseif RELEASE\n        init(x: String) {}\n    #else\n        init() {}\n    #endif"
-            constructor_declaration source=""
-              modifier: modifier "generated" source=""
-              name_node: identifier "init" source=""
-              body: block source=""
+          direct_member:
+            if_expr source="#if ⟨condition⟩\n        ⟨then⟩\n    ⟨else⟩\n    #endif"
+              modifier: modifier "conditional_compilation" source=""
+              condition: identifier "DEBUG" source="DEBUG"
+              then:
+                block source="⟨stmt⟩"
+                  stmt:
+                    constructor_declaration source="⟨name_node⟩(⟨parameter⟩) ⟨body⟩"
+                      name_node: identifier "init" source="init"
+                      parameter:
+                        parameter source="⟨external_name_node⟩⟨pattern⟩: ⟨type⟩"
+                          external_name_node: identifier "x" source="x"
+                          type: identifier "Int" source="Int"
+                          pattern: identifier "x" source="x"
+                      body: block "{}" source="{}"
+              else:
+                if_expr source="#elseif ⟨condition⟩\n        ⟨then⟩\n    ⟨else⟩"
+                  modifier: modifier "conditional_compilation" source=""
+                  condition: identifier "RELEASE" source="RELEASE"
+                  then:
+                    block source="⟨stmt⟩"
+                      stmt:
+                        constructor_declaration source="⟨name_node⟩(⟨parameter⟩) ⟨body⟩"
+                          name_node: identifier "init" source="init"
+                          parameter:
+                            parameter source="⟨external_name_node⟩⟨pattern⟩: ⟨type⟩"
+                              external_name_node: identifier "x" source="x"
+                              type: identifier "String" source="String"
+                              pattern: identifier "x" source="x"
+                          body: block "{}" source="{}"
+                  else:
+                    block source="#else\n        ⟨stmt⟩"
+                      stmt:
+                        constructor_declaration source="⟨name_node⟩() ⟨body⟩"
+                          name_node: identifier "init" source="init"
+                          body: block "{}" source="{}"