[vm] Fix crash when expression evaluating with extension type with type parameter is available

Fixes #59653

Tested: Manually; added pkg/vm_service/test/issue_59653_test.dart and existing tests / CI.
Change-Id: I0969720c4d7c50e8756406477abe791891877abb
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/405381
Commit-Queue: Jens Johansen <[email protected]>
Reviewed-by: Alexander Markov <[email protected]>
Reviewed-by: Derek Xu <[email protected]>

Author: jensjoha

pkg/pkg.status

@@ -163,6 +163,7 @@ vm_service/test/issue_27287_test: SkipByDesign # Debugger is disabled in AOT mod
 vm_service/test/issue_30555_test: SkipByDesign # Debugger is disabled in AOT mode.
 vm_service/test/issue_56911_test: SkipByDesign # Debugger is disabled in AOT mode.
 vm_service/test/issue_57040_test: SkipByDesign # Debugger is disabled in AOT mode.
+vm_service/test/issue_59653_test: SkipByDesign # Debugger is disabled in AOT mode.
 vm_service/test/issue_59661_test: SkipByDesign # Debugger is disabled in AOT mode.
 vm_service/test/kill_paused_test: SkipByDesign # Debugger is disabled in AOT mode.
 vm_service/test/library_dependency_test: SkipByDesign # Uses 'dart:mirrors' library.

pkg/vm_service/test/issue_59653_test.dart

@@ -0,0 +1,64 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:developer';
+import 'common/service_test_common.dart';
+import 'common/test_helper.dart';
+
+// AUTOGENERATED START
+//
+// Update these constants by running:
+//
+// dart pkg/vm_service/test/update_line_numbers.dart pkg/vm_service/test/issue_59653_test.dart
+//
+const LINE_A = 36;
+// AUTOGENERATED END
+
+abstract interface class SharedTypeStructure {}
+
+extension type SharedTypeSchemaView<TypeStructure extends SharedTypeStructure>(
+    TypeStructure _typeStructure) implements Object {}
+
+class C extends SharedTypeStructure {
+  @override
+  String toString() => 'C!';
+}
+
+class ClassWithTypeAnalyzer<TypeStructure extends SharedTypeStructure> {
+  SharedTypeSchemaView<TypeStructure> dispatchExpression(
+    SharedTypeSchemaView<TypeStructure> schema,
+  ) {
+    return schema;
+  }
+
+  void analyzeExpression(SharedTypeSchemaView<TypeStructure> schema) {
+    debugger(); // LINE_A
+  }
+}
+
+void code() {
+  final classWithTypeAnalyzer = ClassWithTypeAnalyzer<C>();
+  classWithTypeAnalyzer.analyzeExpression(SharedTypeSchemaView(C()));
+}
+
+final tests = <IsolateTest>[
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_A),
+  testExpressionEvaluationAndAvailableVariables('analyzeExpression', [
+    'this',
+    'schema',
+  ], [
+    ('1', '1'),
+    ('dispatchExpression(schema).toString()', 'C!'),
+  ]),
+];
+
+void main([args = const <String>[]]) => runIsolateTests(
+      args,
+      tests,
+      'issue_59653_test.dart',
+      testeeConcurrent: code,
+      pauseOnStart: false,
+      pauseOnExit: true,
+    );

runtime/vm/compiler/frontend/kernel_translation_helper.cc

@@ -3586,6 +3586,14 @@ void TypeTranslator::BuildTypeParameterType() {
     const intptr_t class_type_parameter_count =
         active_class_->klass->NumTypeParameters();
     if (class_type_parameter_count > parameter_index) {
+      if (H.GetExpressionEvaluationClass().ptr() ==
+          active_class_->klass->ptr()) {
+        ASSERT(H.GetExpressionEvaluationClass().NumTypeParameters() ==
+               active_class_->klass->NumTypeParameters());
+        result_ = H.GetExpressionEvaluationRealClass().TypeParameterAt(
+            parameter_index, nullability);
+        return;
+      }
       result_ =
           active_class_->klass->TypeParameterAt(parameter_index, nullability);
       return;