Analyzer: Move TOP_LEVEL_CYCLE to be a compile-time error

Also remove duplication with RECURSIVE_COMPILE_TIME_CONSTANT.

Also write some tests for TOP_LEVEL_CYCLE.

Change-Id: I33cb765236a83bd925f9f0c6e65ac9398761c699
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/155701
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

Author: srawlins

pkg/analyzer/lib/error/error.dart

@@ -329,6 +329,7 @@ const List<ErrorCode> errorCodeValues = [
   CompileTimeErrorCode.SUPER_INITIALIZER_IN_OBJECT,
   CompileTimeErrorCode.SWITCH_CASE_COMPLETES_NORMALLY,
   CompileTimeErrorCode.THROW_OF_INVALID_TYPE,
+  CompileTimeErrorCode.TOP_LEVEL_CYCLE,
   CompileTimeErrorCode.TYPE_ALIAS_CANNOT_REFERENCE_ITSELF,
   CompileTimeErrorCode.TYPE_ARGUMENT_NOT_MATCHING_BOUNDS,
   // ignore: deprecated_member_use_from_same_package
@@ -838,7 +839,6 @@ const List<ErrorCode> errorCodeValues = [
   StrongModeCode.IMPLICIT_DYNAMIC_RETURN,
   StrongModeCode.IMPLICIT_DYNAMIC_TYPE,
   StrongModeCode.IMPLICIT_DYNAMIC_VARIABLE,
-  StrongModeCode.TOP_LEVEL_CYCLE,
   StrongModeCode.TOP_LEVEL_FUNCTION_LITERAL_BLOCK,
   StrongModeCode.TOP_LEVEL_IDENTIFIER_NO_TYPE,
   StrongModeCode.TOP_LEVEL_INSTANCE_GETTER,

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

@@ -6254,6 +6254,19 @@ class CompileTimeErrorCode extends AnalyzerErrorCode {
       "The type '{0}' of the thrown expression must be assignable to 'Object'.",
       hasPublishedDocs: true);
 
+  /**
+   * Parameters:
+   * 0: the element whose type could not be inferred.
+   * 1: The [TopLevelInferenceError]'s arguments that led to the cycle.
+   */
+  static const CompileTimeErrorCode TOP_LEVEL_CYCLE = CompileTimeErrorCode(
+      'TOP_LEVEL_CYCLE',
+      "The type of '{0}' can't be inferred because it depends on itself "
+          "through the cycle: {1}.",
+      correction:
+          "Try adding an explicit type to one or more of the variables in the "
+          "cycle in order to break the cycle.");
+
   /**
    * Parameters:
    * 0: the name of the type used in the instance creation that should be
@@ -10853,14 +10866,6 @@ class StrongModeCode extends ErrorCode {
    */
   /* TODO(leafp) Delete most of these.
    */
-  static const StrongModeCode TOP_LEVEL_CYCLE = StrongModeCode(
-      ErrorType.COMPILE_TIME_ERROR,
-      'TOP_LEVEL_CYCLE',
-      "The type of '{0}' can't be inferred because it depends on itself "
-          "through the cycle: {1}.",
-      correction:
-          "Try adding an explicit type to one or more of the variables in the "
-          "cycle in order to break the cycle.");
 
   static const StrongModeCode TOP_LEVEL_FUNCTION_LITERAL_BLOCK = StrongModeCode(
       ErrorType.HINT,

pkg/analyzer/lib/src/task/strong/checker.dart

@@ -1059,8 +1059,12 @@ class _TopLevelInitializerValidator extends RecursiveAstVisitor<void> {
       TopLevelInferenceError error = variable.typeInferenceError;
       if (error != null) {
         if (error.kind == TopLevelInferenceErrorKind.dependencyCycle) {
-          _codeChecker._recordMessage(
-              n, StrongModeCode.TOP_LEVEL_CYCLE, [_name, error.arguments]);
+          // Errors on const should have been reported with
+          // [CompileTimeErrorCode.RECURSIVE_COMPILE_TIME_CONSTANT].
+          if (!variable.isConst) {
+            _codeChecker._recordMessage(n, CompileTimeErrorCode.TOP_LEVEL_CYCLE,
+                [_name, error.arguments]);
+          }
         } else {
           _codeChecker._recordMessage(
               n, StrongModeCode.TOP_LEVEL_IDENTIFIER_NO_TYPE, [_name, e.name]);

pkg/analyzer/test/src/diagnostics/recursive_compile_time_constant_test.dart

@@ -21,9 +21,7 @@ const x = y + 1;
 const y = x + 1;
 ''', [
       error(CompileTimeErrorCode.RECURSIVE_COMPILE_TIME_CONSTANT, 6, 1),
-      error(StrongModeCode.TOP_LEVEL_CYCLE, 10, 1),
       error(CompileTimeErrorCode.RECURSIVE_COMPILE_TIME_CONSTANT, 23, 1),
-      error(StrongModeCode.TOP_LEVEL_CYCLE, 27, 1),
     ]);
   }
 
@@ -72,7 +70,6 @@ class C {
 const x = x;
 ''', [
       error(CompileTimeErrorCode.RECURSIVE_COMPILE_TIME_CONSTANT, 6, 1),
-      error(StrongModeCode.TOP_LEVEL_CYCLE, 10, 1),
     ]);
   }
 
@@ -85,7 +82,6 @@ const elems = const [
 ];
 ''', [
       error(CompileTimeErrorCode.RECURSIVE_COMPILE_TIME_CONSTANT, 6, 5),
-      error(StrongModeCode.TOP_LEVEL_CYCLE, 39, 5),
     ]);
   }
 }

pkg/analyzer/test/src/diagnostics/test_all.dart

@@ -525,6 +525,7 @@ import 'switch_expression_not_assignable_test.dart'
     as switch_expression_not_assignable;
 import 'throw_of_invalid_type_test.dart' as throw_of_invalid_type;
 import 'todo_test.dart' as todo_test;
+import 'top_level_cycle_test.dart' as top_level_cycle;
 import 'top_level_instance_getter_test.dart' as top_level_instance_getter;
 import 'top_level_instance_method_test.dart' as top_level_instance_method;
 import 'type_alias_cannot_reference_itself_test.dart'
@@ -949,6 +950,7 @@ main() {
     switch_expression_not_assignable.main();
     throw_of_invalid_type.main();
     todo_test.main();
+    top_level_cycle.main();
     top_level_instance_getter.main();
     top_level_instance_method.main();
     type_alias_cannot_reference_itself.main();

pkg/analyzer/test/src/diagnostics/top_level_cycle_test.dart

@@ -0,0 +1,47 @@
+// Copyright (c) 2020, 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:analyzer/src/error/codes.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import '../dart/resolution/driver_resolution.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(TopLevelCycleTest);
+  });
+}
+
+@reflectiveTest
+class TopLevelCycleTest extends DriverResolutionTest {
+  test_cycle() async {
+    await assertErrorsInCode(r'''
+var x = y + 1;
+var y = x + 1;
+''', [
+      error(CompileTimeErrorCode.TOP_LEVEL_CYCLE, 8, 1),
+      error(CompileTimeErrorCode.TOP_LEVEL_CYCLE, 23, 1),
+    ]);
+  }
+
+  test_singleVariable() async {
+    await assertErrorsInCode(r'''
+var x = x;
+''', [
+      error(CompileTimeErrorCode.TOP_LEVEL_CYCLE, 8, 1),
+    ]);
+  }
+
+  test_singleVariable_fromList() async {
+    await assertErrorsInCode(r'''
+var elems = [
+  [
+    1, elems, 3,
+  ],
+];
+''', [
+      error(CompileTimeErrorCode.TOP_LEVEL_CYCLE, 25, 5),
+    ]);
+  }
+}

tests/language/const/syntax_test.dart

@@ -95,15 +95,11 @@ const A2 = A3 + 1;
 //    ^^
 // [analyzer] COMPILE_TIME_ERROR.RECURSIVE_COMPILE_TIME_CONSTANT
 // [cfe] Can't infer the type of 'A2': circularity found during type inference.
-//         ^^
-// [analyzer] COMPILE_TIME_ERROR.TOP_LEVEL_CYCLE
 //            ^
 // [cfe] Constant evaluation error:
 const A3 = A2 + 1;
 //    ^^
 // [analyzer] COMPILE_TIME_ERROR.RECURSIVE_COMPILE_TIME_CONSTANT
-//         ^^
-// [analyzer] COMPILE_TIME_ERROR.TOP_LEVEL_CYCLE
 
 class C0 {
   static const X = const C1();

tests/language_2/const/syntax_test.dart

@@ -92,15 +92,11 @@ const A2 = A3 + 1;
 //    ^^
 // [analyzer] COMPILE_TIME_ERROR.RECURSIVE_COMPILE_TIME_CONSTANT
 // [cfe] Can't infer the type of 'A2': circularity found during type inference.
-//         ^^
-// [analyzer] COMPILE_TIME_ERROR.TOP_LEVEL_CYCLE
 //            ^
 // [cfe] Constant evaluation error:
 const A3 = A2 + 1;
 //    ^^
 // [analyzer] COMPILE_TIME_ERROR.RECURSIVE_COMPILE_TIME_CONSTANT
-//         ^^
-// [analyzer] COMPILE_TIME_ERROR.TOP_LEVEL_CYCLE
 
 class C0 {
   static const X = const C1();