add fix for unnecessary_const lints

See: https://github.com/dart-lang/linter/issues/1374.

Change-Id: Ieeddf25718ddde77a9e52cb93cbcf34ca2c1f81f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/95542
Commit-Queue: Phil Quitslund <pquitslund@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analysis_server/lib/src/services/correction/fix.dart

@@ -79,6 +79,7 @@ bool hasFix(ErrorCode errorCode) =>
             errorCode.name == LintNames.prefer_conditional_assignment ||
             errorCode.name == LintNames.prefer_const_declarations ||
             errorCode.name == LintNames.unnecessary_brace_in_string_interp ||
+            errorCode.name == LintNames.unnecessary_const ||
             errorCode.name == LintNames.unnecessary_lambdas ||
             errorCode.name == LintNames.unnecessary_this));
 
@@ -243,6 +244,8 @@ class DartFixKind {
   static const REMOVE_UNNECESSARY_CAST = const FixKind(
       'REMOVE_UNNECESSARY_CAST', 50, "Remove unnecessary cast",
       appliedTogetherMessage: "Remove all unnecessary casts in file");
+  static const REMOVE_UNNECESSARY_CONST = const FixKind(
+      'REMOVE_UNNECESSARY_CONST', 50, "Remove unnecessary const keyword");
   static const REMOVE_UNUSED_CATCH_CLAUSE = const FixKind(
       'REMOVE_UNUSED_CATCH_CLAUSE', 50, "Remove unused 'catch' clause");
   static const REMOVE_UNUSED_CATCH_STACK = const FixKind(

pkg/analysis_server/lib/src/services/correction/fix_internal.dart

@@ -610,6 +610,9 @@ class FixProcessor {
       if (name == LintNames.unnecessary_brace_in_string_interp) {
         await _addFix_removeInterpolationBraces();
       }
+      if (name == LintNames.unnecessary_const) {
+        await _addFix_removeConstKeyword();
+      }
       if (name == LintNames.unnecessary_lambdas) {
         await _addFix_replaceWithTearOff();
       }
@@ -2690,6 +2693,18 @@ class FixProcessor {
     }
   }
 
+  Future<void> _addFix_removeConstKeyword() async {
+    final instanceCreationExpression = node;
+    if (instanceCreationExpression is InstanceCreationExpression) {
+      final constToken = instanceCreationExpression.keyword;
+      var changeBuilder = _newDartChangeBuilder();
+      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
+        builder.addDeletion(range.startStart(constToken, constToken.next));
+      });
+      _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_UNNECESSARY_CONST);
+    }
+  }
+
   Future<void> _addFix_removeDeadCode() async {
     AstNode coveringNode = this.coveredNode;
     if (coveringNode is Expression) {
@@ -4294,6 +4309,7 @@ class LintNames {
   static const String type_init_formals = 'type_init_formals';
   static const String unnecessary_brace_in_string_interp =
       'unnecessary_brace_in_string_interp';
+  static const String unnecessary_const = 'unnecessary_const';
   static const String unnecessary_lambdas = 'unnecessary_lambdas';
   static const String unnecessary_override = 'unnecessary_override';
   static const String unnecessary_this = 'unnecessary_this';

pkg/analysis_server/test/src/services/correction/fix/remove_unnecessary_const_test.dart

@@ -0,0 +1,40 @@
+// Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:analysis_server/src/services/correction/fix.dart';
+import 'package:analysis_server/src/services/correction/fix_internal.dart';
+import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import 'fix_processor.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(UnnecessaryConstTest);
+  });
+}
+
+@reflectiveTest
+class UnnecessaryConstTest extends FixProcessorLintTest {
+  @override
+  FixKind get kind => DartFixKind.REMOVE_UNNECESSARY_CONST;
+
+  @override
+  String get lintCode => LintNames.unnecessary_const;
+
+  test_constConstructor() async {
+    await resolveTestUnit('''
+class A { const A(); }
+m(){
+  const a = /*LINT*/const A();
+}
+''');
+    await assertHasFix('''
+class A { const A(); }
+m(){
+  const a = /*LINT*/A();
+}
+''');
+  }
+}

pkg/analysis_server/test/src/services/correction/fix/test_all.dart

@@ -74,6 +74,7 @@ import 'remove_this_expression_test.dart' as remove_this_expression;
 import 'remove_type_annotation_test.dart' as remove_type_annotation;
 import 'remove_type_arguments_test.dart' as remove_type_arguments;
 import 'remove_unnecessary_cast_test.dart' as remove_unnecessary_cast;
+import 'remove_unnecessary_const_test.dart' as remove_unnecessary_const;
 import 'remove_unused_catch_clause_test.dart' as remove_unused_catch_clause;
 import 'remove_unused_catch_stack_test.dart' as remove_unused_catch_stack;
 import 'remove_unused_import_test.dart' as remove_unused_import;
@@ -159,6 +160,7 @@ main() {
     remove_type_annotation.main();
     remove_type_arguments.main();
     remove_unnecessary_cast.main();
+    remove_unnecessary_const.main();
     remove_unused_catch_clause.main();
     remove_unused_catch_stack.main();
     remove_unused_import.main();