[analyzer] Dot shorthands: FunctionReferences have dot shorthand flag.

`FunctionReference`s like `.foo<T>` can also be dot shorthands. This CL adds the flag onto that AST.

Unit test added and co19 tests that have function references are now passing.

Bug: https://github.com/dart-lang/sdk/issues/59835
Change-Id: I8c85e7915b665de5c4de2b249b22c6e8d8fc364d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/426001
Reviewed-by: Paul Berry <paulberry@google.com>
Commit-Queue: Kallen Tu <kallentu@google.com>

pkg/analyzer/lib/src/dart/ast/ast.dart

@@ -8700,9 +8700,10 @@ abstract final class FunctionReference
   ///
   /// In error-free code, this is either a [SimpleIdentifier] (indicating a
   /// function that is in scope), a [PrefixedIdentifier] (indicating a either
-  /// function imported via prefix or a static method in a class), or a
+  /// function imported via prefix or a static method in a class), a
   /// [PropertyAccess] (indicating a static method in a class imported via
-  /// prefix). In code with errors, this could be other kinds of expressions.
+  /// prefix), or a [DotShorthandPropertyAccess] (indicating a static method in
+  /// a class). In code with errors, this could be other kinds of expressions.
   /// For example, `(...)<int>` parses as a [FunctionReference] whose referent
   /// is a [ParenthesizedExpression].
   Expression get function;
@@ -8720,6 +8721,7 @@ abstract final class FunctionReference
 }
 
 final class FunctionReferenceImpl extends CommentReferableExpressionImpl
+    with DotShorthandMixin
     implements FunctionReference {
   ExpressionImpl _function;
 

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

@@ -2967,11 +2967,22 @@ class ResolverVisitor extends ThrowingAstVisitor<void>
 
   @override
   void visitFunctionReference(
-    FunctionReference node, {
+    covariant FunctionReferenceImpl node, {
     TypeImpl contextType = UnknownInferredType.instance,
   }) {
     inferenceLogWriter?.enterExpression(node, contextType);
-    _functionReferenceResolver.resolve(node as FunctionReferenceImpl);
+
+    // If [isDotShorthand] is set, cache the context type for resolution.
+    if (isDotShorthand(node)) {
+      pushDotShorthandContext(node, SharedTypeSchemaView(contextType));
+    }
+
+    _functionReferenceResolver.resolve(node);
+
+    if (isDotShorthand(node)) {
+      popDotShorthandContext();
+    }
+
     inferenceLogWriter?.exitExpression(node);
   }
 

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

@@ -398,6 +398,38 @@ DotShorthandPropertyAccess
 ''');
   }
 
+  test_functionReference() async {
+    await assertNoErrorsInCode(r'''
+class C<T> {
+  static String foo<X>() => "C<$X>";
+
+  @override
+  bool operator ==(Object other) {
+    return false;
+  }
+}
+
+void test<T extends num>() {
+  C() == .foo<T>;
+}
+
+main() {
+  test<int>();
+}
+''');
+
+    var identifier = findNode.singleDotShorthandPropertyAccess;
+    assertResolvedNodeText(identifier, r'''
+DotShorthandPropertyAccess
+  period: .
+  propertyName: SimpleIdentifier
+    token: foo
+    element: <testLibraryFragment>::@class::C::@method::foo#element
+    staticType: String Function<X>()
+  staticType: String Function<X>()
+''');
+  }
+
   test_futureOr() async {
     await assertNoErrorsInCode('''
 import 'dart:async';