unified: Emit constructor parameters

Emit an initializer's parameters on the `constructor_declaration`,
captured from the `initializerDecl` signature (as for `functionDecl`).
The tree-sitter path dropped them -- its positional `(parameter)*`
capture missed the field-attached parameters -- and the mapping matched
that for corpus parity; swift-syntax exposes them cleanly, so emitting
them is a correctness improvement.

Adds a focused `constructor-with-parameters` corpus case and updates
`class-with-initializer` to witness the restored parameters.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

unified/extractor/src/languages/swift/swift.rs

@@ -1089,18 +1089,18 @@ fn translation_rules() -> Vec<Rule<SwiftContext>> {
         // A member of a type declaration unwraps to the contained declaration.
         rule!((memberBlockItem decl: _* @d) => member* { d }),
         // Init declaration → constructor_declaration. Body statements optional;
-        // body itself is also optional (protocol requirement).
-        //
-        // PARITY(tree-sitter): the parameters are not emitted, because the
-        // tree-sitter path dropped them (its `(parameter)*` capture missed the
-        // field-attached parameters). Emitting them is a future improvement.
+        // body itself is also optional (protocol requirement). The parameters
+        // nest under `signature` (as for `functionDecl`).
         rule!(
             (initializerDecl
                 modifiers: _* @mods
+                signature: (functionSignature
+                    parameterClause: (functionParameterClause parameters: _* @params))
                 body: (codeBlock statements: _* @body_stmts)?)
             =>
             (constructor_declaration
                 modifier: {mods}
+                parameter: {params}
                 body: (block stmt: {body_stmts}))
         ),
         // Deinit declaration → destructor_declaration. Body statements optional.

unified/extractor/tests/corpus/swift/types/class-with-initializer.output

@@ -103,6 +103,11 @@ top_level
                 named_type_expr
                   name: identifier "Int"
             constructor_declaration
+              parameter:
+                parameter
+                  pattern:
+                    name_pattern
+                      identifier: identifier "x"
               body:
                 block
                   stmt:

unified/extractor/tests/corpus/swift/types/constructor-with-parameters.output

@@ -0,0 +1,82 @@
+struct Size {
+  init(width w: Int, height h: Int) {}
+}
+
+---
+
+sourceFile
+  endOfFileToken: endOfFile
+  statements:
+    codeBlockItem
+      item:
+        structDecl
+          attributes:
+          name: identifier "Size"
+          memberBlock:
+            memberBlock
+              leftBrace: {
+              rightBrace: }
+              members:
+                memberBlockItem
+                  decl:
+                    initializerDecl
+                      attributes:
+                      body:
+                        codeBlock
+                          leftBrace: {
+                          rightBrace: }
+                          statements:
+                      modifiers:
+                      signature:
+                        functionSignature
+                          parameterClause:
+                            functionParameterClause
+                              leftParen: (
+                              rightParen: )
+                              parameters:
+                                functionParameter
+                                  colon: :
+                                  attributes:
+                                  modifiers:
+                                  trailingComma: ,
+                                  type:
+                                    identifierType
+                                      name: identifier "Int"
+                                  firstName: identifier "width"
+                                  secondName: identifier "w"
+                                functionParameter
+                                  colon: :
+                                  attributes:
+                                  modifiers:
+                                  type:
+                                    identifierType
+                                      name: identifier "Int"
+                                  firstName: identifier "height"
+                                  secondName: identifier "h"
+                      initKeyword: init
+          modifiers:
+          structKeyword: struct
+
+---
+
+top_level
+  body:
+    block
+      stmt:
+        class_like_declaration
+          modifier: modifier "struct"
+          name: identifier "Size"
+          member:
+            constructor_declaration
+              parameter:
+                parameter
+                  external_name: identifier "width"
+                  pattern:
+                    name_pattern
+                      identifier: identifier "w"
+                parameter
+                  external_name: identifier "height"
+                  pattern:
+                    name_pattern
+                      identifier: identifier "h"
+              body: block "init(width w: Int, height h: Int) {}"

unified/extractor/tests/corpus/swift/types/constructor-with-parameters.swift

@@ -0,0 +1,3 @@
+struct Size {
+  init(width w: Int, height h: Int) {}
+}