[analyzer] Dot shorthands: Report error when instantiating abstract class.

This CL reports `INSTANTIATE_ABSTRACT_CLASS` when we are trying to instantiate an abstract class (with a non-factory constructor).

co19 tests and unit tests passing.

Bug: #59835
Change-Id: I5eded14f558d528265d82fd63cc0af3d9b052eac
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/426682
Reviewed-by: Chloe Stefantsova <[email protected]>
Commit-Queue: Kallen Tu <[email protected]>

Author: kallentu

pkg/analyzer/lib/src/dart/resolver/instance_creation_expression_resolver.dart

@@ -73,12 +73,12 @@ class InstanceCreationExpressionResolver {
 
     // TODO(kallentu): Support other context types
     if (dotShorthandContextType is InterfaceTypeImpl) {
+      InterfaceElementImpl2? contextElement = dotShorthandContextType.element3;
       // This branch will be true if we're resolving an explicitly marked
       // const constructor invocation. It's completely unresolved, unlike a
       // rewritten [DotShorthandConstructorInvocation] that resulted from
       // resolving a [DotShorthandInvocation].
       if (node.element == null) {
-        var contextElement = dotShorthandContextType.element3;
         if (contextElement.getNamedConstructor2(node.constructorName.name)
             case ConstructorElementImpl2 element?
             when element.isAccessibleIn2(_resolver.definingLibrary)) {
@@ -93,7 +93,15 @@ class InstanceCreationExpressionResolver {
       }
 
       var typeArguments = node.typeArguments;
-      if (typeArguments != null) {
+      if (contextElement is ClassElementImpl2 && contextElement.isAbstract) {
+        var constructorElement = node.element;
+        if (constructorElement != null && !constructorElement.isFactory) {
+          _resolver.errorReporter.atNode(
+            node,
+            CompileTimeErrorCode.INSTANTIATE_ABSTRACT_CLASS,
+          );
+        }
+      } else if (typeArguments != null) {
         _resolver.errorReporter.atNode(
           typeArguments,
           CompileTimeErrorCode

pkg/analyzer/test/src/dart/resolution/dot_shorthand_constructor_invocation_test.dart

@@ -18,6 +18,52 @@ main() {
 @reflectiveTest
 class DotShorthandConstructorInvocationResolutionTest
     extends PubPackageResolutionTest {
+  test_abstract_instantiation() async {
+    await assertErrorsInCode(
+      r'''
+Function getFunction() {
+  return .new();
+}
+''',
+      [error(CompileTimeErrorCode.INSTANTIATE_ABSTRACT_CLASS, 34, 6)],
+    );
+  }
+
+  test_abstract_instantiation_factory() async {
+    await assertNoErrorsInCode(r'''
+void main() async {
+  var iter = [1, 2];
+  await for (var x in .fromIterable(iter)) {
+    print(x);
+  }
+}
+''');
+
+    var node = findNode.singleDotShorthandConstructorInvocation;
+    assertResolvedNodeText(node, r'''
+DotShorthandConstructorInvocation
+  period: .
+  constructorName: SimpleIdentifier
+    token: fromIterable
+    element: ConstructorMember
+      baseElement: dart:async::@fragment::dart:async/stream.dart::@class::Stream::@constructor::fromIterable#element
+      substitution: {T: int}
+    staticType: null
+  argumentList: ArgumentList
+    leftParenthesis: (
+    arguments
+      SimpleIdentifier
+        token: iter
+        correspondingParameter: ParameterMember
+          baseElement: dart:async::@fragment::dart:async/stream.dart::@class::Stream::@constructor::fromIterable::@parameter::data#element
+          substitution: {T: int}
+        element: iter@26
+        staticType: List<int>
+    rightParenthesis: )
+  staticType: Stream<int>
+''');
+  }
+
   test_chain_method() async {
     await assertNoErrorsInCode(r'''
 class C {