[analysis_server] Use generic function syntax for function parameters…

… in "Extract Method"

This fixes an issue where parameters that used the new function syntax and had no parameter names would produce code like `void f(String )` where the type would be interpreted as a parameter name and typed `dynamic`.

Fixes Dart-Code/Dart-Code#5350

Change-Id: Ifcbe64dadb88cc0fd9b4fa3637045bcdc343f3f7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/397900
Reviewed-by: Brian Wilkerson <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>

pkg/analysis_server/lib/src/services/refactoring/legacy/extract_method.dart

@@ -353,12 +353,14 @@ final class ExtractMethodRefactoringImpl extends RefactoringImpl
             sb.write(' ');
           }
         }
-        // name
-        sb.write(parameter.name);
         // optional function-typed parameter parameters
         if (parameter.parameters != null) {
+          sb.write('Function');
           sb.write(parameter.parameters);
+          sb.write(' ');
         }
+        // name
+        sb.write(parameter.name);
       }
       sb.write(')');
     }
@@ -1849,8 +1851,10 @@ extension on LibraryElement {
           parametersBuffer.write(', ');
         }
         parametersBuffer.write(parameterType);
-        parametersBuffer.write(' ');
-        parametersBuffer.write(parameter.name);
+        if (parameter.name.isNotEmpty) {
+          parametersBuffer.write(' ');
+          parametersBuffer.write(parameter.name);
+        }
       }
       parametersBuffer.write(')');
       return getTypeSource(type.returnType, librariesToImport);

pkg/analysis_server/test/services/refactoring/legacy/extract_method_test.dart

@@ -3377,7 +3377,7 @@ class C {
     return d;
   }
 
-  int res(int callback(int x, int y), int b) {
+  int res(int Function(int x, int y) callback, int b) {
     int c = callback(b, 2);
     return c;
   }
@@ -3604,6 +3604,53 @@ int res() {
 ''');
   }
 
+  Future<void> test_statements_topFunction_parameters_function() async {
+    await indexTestUnit('''
+Future<void> f(void f(String x), String a) async {
+// start
+  f(a);
+// end
+}
+''');
+    _createRefactoringForStartEndComments();
+    // apply refactoring
+    return _assertSuccessfulRefactoring('''
+Future<void> f(void f(String x), String a) async {
+// start
+  res(f, a);
+// end
+}
+
+void res(void Function(String x) f, String a) {
+  f(a);
+}
+''');
+  }
+
+  Future<void>
+  test_statements_topFunction_parameters_function_functionSyntax() async {
+    await indexTestUnit('''
+Future<void> f(void Function(String) f, String a) async {
+// start
+  f(a);
+// end
+}
+''');
+    _createRefactoringForStartEndComments();
+    // apply refactoring
+    return _assertSuccessfulRefactoring('''
+Future<void> f(void Function(String) f, String a) async {
+// start
+  res(f, a);
+// end
+}
+
+void res(void Function(String) f, String a) {
+  f(a);
+}
+''');
+  }
+
   Future<void> test_statements_topFunction_parameters_recordType() async {
     await indexTestUnit('''
 void f((int, String) r) {