Elements. Fixes after https://dart-review.googlesource.com/c/sdk/+/405660

Bug: https://buganizer.corp.google.com/issues/392069763
Change-Id: Iecbfc55433890c4e5e606dc9b1f2bc005b9b6684
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/405800
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analyzer/lib/src/dart/element/inheritance_manager3.dart

@@ -1397,7 +1397,7 @@ class Name {
     }
 
     if (name.startsWith('_')) {
-      var libraryUri = element.firstFragment.libraryFragment!.source.uri;
+      var libraryUri = element.library2!.uri;
       return Name(libraryUri, name);
     } else {
       return Name(null, name);

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

@@ -91,12 +91,13 @@ class ExtensionMemberResolver {
   /// returns [ExtensionResolutionError.ambiguous].
   ExtensionResolutionResult findExtension(
       TypeImpl type, SyntacticEntity nameEntity, Name name) {
-    var aaa = _resolver.libraryFragment.accessibleExtensions2;
-    var bbb = aaa.havingMemberWithBaseName(name).toList();
-    var extensions = bbb.applicableTo(
-      targetLibrary: _resolver.definingLibrary,
-      targetType: type,
-    );
+    var extensions = _resolver.libraryFragment.accessibleExtensions2
+        .havingMemberWithBaseName(name)
+        .toList()
+        .applicableTo(
+          targetLibrary: _resolver.definingLibrary,
+          targetType: type,
+        );
 
     if (extensions.isEmpty) {
       return ExtensionResolutionError.none;

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

@@ -1653,6 +1653,73 @@ MethodInvocation
 ''');
   }
 
+  test_instance_method_fromInstance_privateName() async {
+    await assertNoErrorsInCode('''
+extension E on int {
+  void _foo() {}
+}
+
+void f() {
+  0._foo();
+}
+''');
+    var invocation = findNode.methodInvocation('_foo();');
+    assertResolvedNodeText(invocation, r'''
+MethodInvocation
+  target: IntegerLiteral
+    literal: 0
+    staticType: int
+  operator: .
+  methodName: SimpleIdentifier
+    token: _foo
+    staticElement: <testLibraryFragment>::@extension::E::@method::_foo
+    element: <testLibraryFragment>::@extension::E::@method::_foo#element
+    staticType: void Function()
+  argumentList: ArgumentList
+    leftParenthesis: (
+    rightParenthesis: )
+  staticInvokeType: void Function()
+  staticType: void
+''');
+  }
+
+  test_instance_method_fromInstance_privateName_inPart() async {
+    newFile('$testPackageLibPath/a.dart', r'''
+part of 'test.dart';
+
+extension E on int {
+  void _foo() {}
+}
+''');
+
+    await assertNoErrorsInCode('''
+part 'a.dart';
+
+void f() {
+  0._foo();
+}
+''');
+
+    var invocation = findNode.methodInvocation('_foo();');
+    assertResolvedNodeText(invocation, r'''
+MethodInvocation
+  target: IntegerLiteral
+    literal: 0
+    staticType: int
+  operator: .
+  methodName: SimpleIdentifier
+    token: _foo
+    staticElement: <testLibrary>::@fragment::package:test/a.dart::@extension::E::@method::_foo
+    element: <testLibrary>::@fragment::package:test/a.dart::@extension::E::@method::_foo#element
+    staticType: void Function()
+  argumentList: ArgumentList
+    leftParenthesis: (
+    rightParenthesis: )
+  staticInvokeType: void Function()
+  staticType: void
+''');
+  }
+
   test_instance_method_specificSubtypeMatchLocal() async {
     await assertNoErrorsInCode('''
 class A {}