Issue 37401. Support for const Set default values in mocks.

Bug: #37401
Change-Id: Ia65a0e6204f64a308dd27810759a8b7416244248
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/108841
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Vijay Menon <[email protected]>

Author: scheglov

pkg/dev_compiler/lib/src/analyzer/code_generator.dart

@@ -4511,6 +4511,10 @@ class CodeGenerator extends Object
         return _emitConstList(type.typeArguments[0],
             value.toListValue().map(_emitDartObject).toList());
       }
+      if (type.element == types.setType.element) {
+        return _emitConstSet(type.typeArguments[0],
+            value.toSetValue().map(_emitDartObject).toList());
+      }
       if (type.element == types.mapType.element) {
         var entries = <js_ast.Expression>[];
         value.toMapValue().forEach((key, value) {
@@ -5811,6 +5815,12 @@ class CodeGenerator extends Object
     return _emitType(type.instantiate(typeArgs));
   }
 
+  js_ast.Expression _emitConstSet(
+      DartType elementType, List<js_ast.Expression> elements) {
+    return cacheConst(
+        runtimeCall('constSet([#], #)', [elements, _emitType(elementType)]));
+  }
+
   js_ast.Expression _emitSetImplType(InterfaceType type, {bool identity}) {
     var typeArgs = type.typeArguments;
     if (typeArgs.isEmpty) return _emitType(type);