Fix "Convert to a primary constructor" on generic classes.

It would incorrectly put the primary constructor parameter list before
the type's type parameter list, like:

```dart
// Before:
class C<T> {
  C();
}

// After:
class C()<T> {
}
```

This fixes it to follow the type parameter list if there is one.

Change-Id: Ib49c7df7923e9feed11f87579fefc8300c56c4a6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/506760
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Auto-Submit: Bob Nystrom <rnystrom@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Bob Nystrom <rnystrom@google.com>

pkg/analysis_server/lib/src/services/correction/dart/convert_to_primary_constructor.dart

@@ -68,13 +68,16 @@ class ConvertToPrimaryConstructor extends ResolvedCorrectionProducer {
       if (constructor.constKeyword != null && !containerData.isEnum) {
         builder.addSimpleInsertion(containerData.name.offset, 'const ');
       }
-      builder.addInsertion(containerData.name.end, (builder) {
-        if (constructor.name case var name?) {
-          builder.write('.');
-          builder.write(name.lexeme);
-        }
-        builder.write(_parameterText(constructor.parameters));
-      });
+      builder.addInsertion(
+        containerData.typeParameters?.end ?? containerData.name.end,
+        (builder) {
+          if (constructor.name case var name?) {
+            builder.write('.');
+            builder.write(name.lexeme);
+          }
+          builder.write(_parameterText(constructor.parameters));
+        },
+      );
 
       // Remove the constructor that was converted.
       //
@@ -104,39 +107,24 @@ class ConvertToPrimaryConstructor extends ResolvedCorrectionProducer {
   /// Returns information about the declaration in which the [constructor] is
   /// declared.
   _ContainerData? _getContainerData(ConstructorDeclaration constructor) {
-    Token name;
-    bool hasPrimaryConstructor;
-    int nonRedirectingGenerativeConstructorCount;
-    bool isEnum = false;
-    var parent = constructor.parent;
-    switch (parent) {
-      case BlockClassBody body:
-        parent = body.parent;
-      case BlockEnumBody body:
-        parent = body.parent;
-    }
-    switch (parent) {
-      case ClassDeclaration(:var namePart):
-        name = namePart.typeName;
-        hasPrimaryConstructor = namePart is PrimaryConstructorDeclaration;
-        nonRedirectingGenerativeConstructorCount =
-            _nonRedirectingGenerativeConstructorCount(parent.classMembers);
-      case EnumDeclaration(:var namePart):
-        name = namePart.typeName;
-        hasPrimaryConstructor = namePart is PrimaryConstructorDeclaration;
-        nonRedirectingGenerativeConstructorCount =
-            _nonRedirectingGenerativeConstructorCount(parent.classMembers);
-        isEnum = true;
-      default:
-        return null;
-    }
-    return _ContainerData(
-      name: name,
-      hasPrimaryConstructor: hasPrimaryConstructor,
-      hasMultipleNonRedirectingGenerativeConstructors:
-          nonRedirectingGenerativeConstructorCount > 1,
-      isEnum: isEnum,
-    );
+    var parent = switch (constructor.parent) {
+      BlockClassBody body => body.parent,
+      BlockEnumBody body => body.parent,
+      var parent => parent,
+    };
+
+    return switch (parent) {
+      ClassDeclaration(:var namePart) ||
+      EnumDeclaration(:var namePart) => _ContainerData(
+        name: namePart.typeName,
+        typeParameters: namePart.typeParameters,
+        hasPrimaryConstructor: namePart is PrimaryConstructorDeclaration,
+        hasMultipleNonRedirectingGenerativeConstructors:
+            _nonRedirectingGenerativeConstructorCount(parent.classMembers) > 1,
+        isEnum: parent is EnumDeclaration,
+      ),
+      _ => null,
+    };
   }
 
   /// Returns the number of non-redirecting generative constructors in the list
@@ -163,6 +151,10 @@ class _ContainerData {
   /// The name of the class or enum.
   Token name;
 
+  /// The type parameters on the class or enum or `null` if the type isn't
+  /// generic.
+  TypeParameterList? typeParameters;
+
   /// Whether the class or enum already has a primary constructor.
   bool hasPrimaryConstructor;
 
@@ -175,6 +167,7 @@ class _ContainerData {
 
   _ContainerData({
     required this.name,
+    required this.typeParameters,
     required this.hasPrimaryConstructor,
     required this.hasMultipleNonRedirectingGenerativeConstructors,
     required this.isEnum,

pkg/analysis_server/test/src/services/correction/assist/convert_to_primary_constructor_test.dart

@@ -20,6 +20,18 @@ class ConvertToPrimaryConstructorClassTest extends AssistProcessorTest {
   @override
   AssistKind get kind => DartAssistKind.convertToPrimaryConstructor;
 
+  Future<void> test_genericClass() async {
+    await resolveTestCode('''
+class C<T> {
+  C^();
+}
+''');
+    await assertHasAssist('''
+class C<T>() {
+}
+''');
+  }
+
   Future<void> test_noParameters_noBody_named() async {
     await resolveTestCode('''
 class C {
@@ -483,6 +495,20 @@ class ConvertToPrimaryConstructorEnumTest extends AssistProcessorTest {
   @override
   AssistKind get kind => DartAssistKind.convertToPrimaryConstructor;
 
+  Future<void> test_genericEnum() async {
+    await resolveTestCode('''
+enum C<T> {
+  a;
+  C^();
+}
+''');
+    await assertHasAssist('''
+enum C<T>() {
+  a;
+}
+''');
+  }
+
   Future<void> test_noParameters_noBody() async {
     await resolveTestCode('''
 enum E {