[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]>

Author: DanTup

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) {