diagnostic for static extension member access

Change-Id: I5380fa6240434ff398cdbd7efeae32b11336cf69
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/109681
Commit-Queue: Phil Quitslund <pquitslund@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analyzer/lib/error/error.dart

@@ -65,6 +65,7 @@ const List<ErrorCode> errorCodeValues = const [
   CheckedModeCompileTimeErrorCode.VARIABLE_TYPE_MISMATCH,
   CompileTimeErrorCode.ABSTRACT_SUPER_MEMBER_REFERENCE,
   CompileTimeErrorCode.ACCESS_PRIVATE_ENUM_FIELD,
+  CompileTimeErrorCode.ACCESS_STATIC_EXTENSION_MEMBER,
   CompileTimeErrorCode.AMBIGUOUS_EXPORT,
   CompileTimeErrorCode.AMBIGUOUS_EXTENSION_METHOD_ACCESS,
   CompileTimeErrorCode.AMBIGUOUS_SET_OR_MAP_LITERAL_BOTH,

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

@@ -299,6 +299,10 @@ class MethodInvocationResolver {
     return invokeType;
   }
 
+  /// Ask the type system to instantiate the given type to its bounds.
+  DartType _instantiateToBounds(DartType type) =>
+      _resolver.typeSystem.instantiateToBounds(type);
+
   bool _isCoreFunction(DartType type) {
     // TODO(scheglov) Can we optimize this?
     return type is InterfaceType && type.isDartCoreFunction;
@@ -413,6 +417,23 @@ class MethodInvocationResolver {
     return null;
   }
 
+  void _resolveExtension(MethodInvocation node, ExtensionElement extension,
+      SimpleIdentifier nameNode, String name) {
+    ExecutableElement member = extension.getMethod(name) ??
+        extension.getGetter(name) ??
+        extension.getSetter(name);
+    if (member.isStatic) {
+      _setDynamicResolution(node);
+      _resolver.errorReporter.reportErrorForNode(
+        CompileTimeErrorCode.ACCESS_STATIC_EXTENSION_MEMBER,
+        nameNode,
+      );
+      return;
+    }
+    nameNode.staticElement = member;
+    return;
+  }
+
   void _resolveExtensionOverride(MethodInvocation node,
       ExtensionOverride override, SimpleIdentifier nameNode, String name) {
     ExtensionElement element = override.extensionName.staticElement;
@@ -499,12 +520,7 @@ class MethodInvocationResolver {
     List<ExtensionElement> extensions =
         _getApplicableExtensions(receiverType, name);
     if (extensions.length == 1) {
-      var extension = extensions[0];
-      Element member = extension.getMethod(name) ??
-          extension.getGetter(name) ??
-          extension.getSetter(name);
-      nameNode.staticElement = member;
-      return;
+      return _resolveExtension(node, extensions[0], nameNode, name);
     } else if (extensions.length > 1) {
       ExtensionElement extension =
           _chooseMostSpecificExtension(extensions, receiverType);
@@ -521,11 +537,7 @@ class MethodInvocationResolver {
         );
         return;
       } else {
-        ExecutableElement member = extension.getMethod(name) ??
-            extension.getGetter(name) ??
-            extension.getSetter(name);
-        nameNode.staticElement = member;
-        return;
+        return _resolveExtension(node, extension, nameNode, name);
       }
     }
 
@@ -788,10 +800,6 @@ class MethodInvocationResolver {
     _reportInvocationOfNonFunction(node);
   }
 
-  /// Ask the type system to instantiate the given type to its bounds.
-  DartType _instantiateToBounds(DartType type) =>
-      _resolver.typeSystem.instantiateToBounds(type);
-
   /// Ask the type system for a subtype check.
   bool _subtypeOf(DartType type1, DartType type2) =>
       _resolver.typeSystem.isSubtypeOf(type1, type2);

pkg/analyzer/lib/src/error/codes.dart

@@ -125,6 +125,15 @@ class CompileTimeErrorCode extends ErrorCode {
           "The private fields of an enum can't be accessed, even within the "
               "same library.");
 
+  /**
+   * No parameters.
+   */
+  //todo (pq): refactor to reuse StaticTypeWarningCode.INSTANCE_ACCESS_TO_STATIC_MEMBER.
+  static const CompileTimeErrorCode ACCESS_STATIC_EXTENSION_MEMBER =
+      const CompileTimeErrorCode('ACCESS_STATIC_EXTENSION_MEMBER',
+          "Static extension members can't be accessed.",
+          correction: "Try removing the static member access.");
+
   /**
    * 14.2 Exports: It is a compile-time error if a name <i>N</i> is re-exported
    * by a library <i>L</i> and <i>N</i> is introduced into the export namespace

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

@@ -115,6 +115,23 @@ f() {
     expect(invocation.methodName.staticElement, declaration.declaredElement);
   }
 
+  test_method_resolvesToStatic() async {
+    await assertErrorsInCode('''
+class A { }
+
+extension A1_Ext on A {
+  static void a() { }
+}
+
+f() {
+  A a = A();
+  a.a();
+}
+''', [
+      error(CompileTimeErrorCode.ACCESS_STATIC_EXTENSION_MEMBER, 85, 1),
+    ]);
+  }
+
   test_method_specificSubtypeMatchLocal() async {
     await assertNoErrorsInCode('''
 class A { }