Issue 36890. Ignore the name that contains the caret during completion.

The previous implementation worked fine in tests, when we asked for
completion where the user does, but that's not what happens during
actual completion. Actually the 'offset' is at the start of the
identifier.

R=brianwilkerson@google.com

Bug: #36890
Change-Id: I5ceaff055580a18fe34d2c17ccacef8f4c7663b3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/108282
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

Author: scheglov

pkg/analyzer_plugin/lib/src/utilities/change_builder/dart/syntactic_scope.dart

@@ -300,7 +300,7 @@ class SyntacticScopeNamesCollector extends RecursiveAstVisitor<void> {
 
   void _addName(SimpleIdentifier node) {
     if (node == null) return;
-    if (node.end == offset) return;
+    if (node.offset <= offset && offset <= node.end) return;
 
     names.add(node.name);
   }

pkg/analyzer_plugin/test/src/utilities/change_builder/dart/import_library_element_test.dart

@@ -205,21 +205,34 @@ class C {
     );
   }
 
-  test_formalParameter() async {
-    newFile('/home/test/lib/a.dart', content: 'class A {}');
-    newFile('/home/test/lib/b.dart', content: r'''
-export 'a.dart';
-''');
+  test_formalParameter_end() async {
+    newFile('/home/test/lib/a.dart', content: 'class AAA {}');
     await _assertImportLibraryElement(
       initialCode: r'''
-f(A^) {}
+f(AAA^) {}
 ''',
       uriStr: 'package:test/a.dart',
-      name: 'A',
+      name: 'AAA',
+      expectedCode: r'''
+import 'package:test/a.dart';
+
+f(AAA) {}
+''',
+    );
+  }
+
+  test_formalParameter_start() async {
+    newFile('/home/test/lib/a.dart', content: 'class AAA {}');
+    await _assertImportLibraryElement(
+      initialCode: r'''
+f(^AAA) {}
+''',
+      uriStr: 'package:test/a.dart',
+      name: 'AAA',
       expectedCode: r'''
 import 'package:test/a.dart';
 
-f(A) {}
+f(AAA) {}
 ''',
     );
   }

pkg/analyzer_plugin/test/src/utilities/change_builder/dart/syntactic_scope_test.dart

@@ -352,6 +352,18 @@ N1 N2(N3 N4(N5 N6 ^1, N7), N8 ^2) {
 ''');
   }
 
+  test_FormalParameter_nameOnly() {
+    _assertScopeNames(code: r'''
+N1 N2(^1N3^2) {
+  ^3
+}
+''', expected: r'''
+1: {}
+2: {}
+3: N3
+''');
+  }
+
   test_ForStatement2_ForEachPartsWithDeclaration() {
     _enableExperiments();
     _assertScopeNames(code: r'''