[ffigen] Fix function type param name bug

pkgs/ffigen/CHANGELOG.md

@@ -9,6 +9,8 @@
   `Declarations.includeMemberSet`, `Declarations.useOriginalName`,
   `Declarations.renameWithMap`, `Declarations.useMemberOriginalName`, and
   `Declarations.renameMemberWithMap`.
+- Fix [a bug](https://github.com/dart-lang/native/issues/2795) where function
+  pointer param names could collide with keywords.
 - Fix [a bug](https://github.com/dart-lang/native/issues/2782) where unnamed
   enum constants were being multiply defined.
 - Fix [a bug](https://github.com/dart-lang/native/issues/2761) in imported

pkgs/ffigen/lib/src/code_generator/func_type.dart

@@ -30,8 +30,13 @@ class FunctionType extends Type with HasLocalScope {
     String? varArgWrapper,
   }) {
     final params = varArgWrapper != null ? parameters : dartTypeParameters;
-    String paramToString(Parameter p) =>
-        '${typeToString(p.type)} ${writeArgumentNames ? p.originalName : ""}';
+    String paramToString(Parameter p) {
+      final name = writeArgumentNames && p.originalName.isNotEmpty
+          ? p.name
+          : '';
+      return '${typeToString(p.type)} $name';
+    }
+
     String? varArgPack;
     if (varArgWrapper != null && varArgParameters.isNotEmpty) {
       final varArgPackBuf = StringBuffer();

pkgs/ffigen/test/collision_tests/expected_bindings/_expected_reserved_keyword_collision_bindings.dart

@@ -36,6 +36,13 @@ class NativeLibrary {
   set import(int value) => _import.value = value;
 }
 
+final class Repro2795 extends ffi.Struct {
+  external ffi.Pointer<
+    ffi.NativeFunction<ffi.Void Function(ffi.Pointer<ffi.Void> in$)>
+  >
+  var$1;
+}
+
 final class abstract$ extends ffi.Opaque {}
 
 enum export$ {

pkgs/ffigen/test/collision_tests/reserved_keyword_collision.h

@@ -8,3 +8,8 @@ enum export { covariant };
 void implements(int dynamic, int in, int deferred) {}
 int import = 123;
 typedef void var;
+
+// Regression test for https://github.com/dart-lang/native/issues/2795
+struct Repro2795 {
+  void (*var)(void* in);
+};