Deprecate FallThroughError.

The error has not been thrown since Dart 2.0,
where being able to reach the end of a switch case
became a compile-time error.

TEST=Removes tests depending on discontinued behavior.

Change-Id: I76292e7c73f2b3aaf071bbb290e97db493b75477
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/261860
Reviewed-by: Michael Thomsen <[email protected]>
Commit-Queue: Lasse Nielsen <[email protected]>
Auto-Submit: Lasse Nielsen <[email protected]>
Reviewed-by: Brian Quinlan <[email protected]>

Author: lrhn

CHANGELOG.md

@@ -70,6 +70,11 @@
 [#34233]: https://github.com/dart-lang/sdk/issues/34233
 [`DEFAULT_BUFFER_SIZE`]: https://api.dart.dev/stable/2.17.6/dart-convert/JsonUtf8Encoder/DEFAULT_BUFFER_SIZE-constant.html
 
+#### `dart:core`
+
+- Deprecated `FallThroughError`. Has not been thrown since Dart 2.0.
+  See [#24233][].
+
 #### `dart:developer`
 
 - **Breaking change** [#34233][]: The previously deprecated APIs

pkg/test_runner/lib/src/static_error.dart

@@ -312,7 +312,7 @@ class StaticError implements Comparable<StaticError> {
         return false;
     }
 
-    throw FallThroughError();
+    throw UnsupportedError("ErrorSource ${source.name}");
   }
 
   String toString() {

runtime/tests/concurrency/generate_stress_test_list.dart

@@ -68,7 +68,7 @@ Future<List<String>> findValidTests(List<String> directories, bool nnbd) async {
       'The following tests were filtered due to using blacklisted things:');
 
   for (int i = 0; i < testFiles.length; ++i) {
-    testFiles[i] = path.relative(testFiles[i], from: thisDir);
+    testFiles[i] = path.relative(testFiles[i], from: thisDirectory);
   }
   if (File(tempFile).existsSync()) {
     File(tempFile).deleteSync();

runtime/tests/concurrency/stress_test_list.json

@@ -2555,7 +2555,6 @@
     "../../../tests/language/switch/case_expression_with_assignment_runtime_test.dart",
     "../../../tests/language/switch/case_runtime_test.dart",
     "../../../tests/language/switch/case_static_const_test.dart",
-    "../../../tests/language/switch/fallthru_runtime_test.dart",
     "../../../tests/language/switch/infinite_switch_label_test.dart",
     "../../../tests/language/switch/label2_test.dart",
     "../../../tests/language/switch/label_test.dart",
@@ -5888,7 +5887,6 @@
     "../../../tests/language_2/switch/case_expression_with_assignment_runtime_test.dart",
     "../../../tests/language_2/switch/case_runtime_test.dart",
     "../../../tests/language_2/switch/case_static_const_test.dart",
-    "../../../tests/language_2/switch/fallthru_runtime_test.dart",
     "../../../tests/language_2/switch/infinite_switch_label_test.dart",
     "../../../tests/language_2/switch/label2_test.dart",
     "../../../tests/language_2/switch/label_test.dart",

runtime/vm/exceptions.cc

@@ -1143,11 +1143,6 @@ ObjectPtr Exceptions::Create(ExceptionType type, const Array& arguments) {
       class_name = &Symbols::TypeError();
       constructor_name = &Symbols::DotCreate();
       break;
-    case kFallThrough:
-      library = Library::CoreLibrary();
-      class_name = &Symbols::FallThroughError();
-      constructor_name = &Symbols::DotCreate();
-      break;
     case kAbstractClassInstantiation:
       library = Library::CoreLibrary();
       class_name = &Symbols::AbstractClassInstantiationError();

runtime/vm/exceptions.h

@@ -66,7 +66,6 @@ class Exceptions : AllStatic {
     kAssertion,
     kCast,
     kType,
-    kFallThrough,
     kAbstractClassInstantiation,
     kCyclicInitializationError,
     kCompileTimeError,

sdk/lib/core/errors.dart

@@ -451,12 +451,14 @@ class IndexError extends ArgumentError implements RangeError {
   }
 }
 
-/// Error thrown when control reaches the end of a switch case.
+/// Error previously thrown when control reaches the end of a switch case.
 ///
-/// The Dart specification requires this error to be thrown when
-/// control reaches the end of a switch case (except the last case
-/// of a switch) without meeting a break or similar end of the control
-/// flow.
+/// The pre-2.0 Dart specification required this error to be thrown when
+/// control reached the end of a switch case (except the last case
+/// of a switch) without meeting a `break` or other control flow operators.
+/// That kind of fall-through was made a compile-time error Dart 2.0,
+/// so this error no longer thrown.
+@Deprecated("No longer relevant in Dart 2.0")
 class FallThroughError extends Error {
   FallThroughError();
   @pragma("vm:entry-point")

tests/language/switch/empty_block_case_test.dart

@@ -14,17 +14,12 @@ import "package:expect/expect.dart";
 class EmptyBlockCaseTest {
   static testMain() {
     var exception = null;
-    try {
-      switch (1) {
-        case 1: /*@compile-error=unspecified*/
-          {}
-        case 2:
-          Expect.equals(true, false);
-      }
-    } on FallThroughError catch (e) {
-      exception = e;
+    switch (1) {
+      case 1: /*@compile-error=unspecified*/
+        {}
+      case 2:
+        Expect.equals(true, false);
     }
-    Expect.equals(true, exception != null);
   }
 }
 

tests/language/switch/fallthru_runtime_test.dart

@@ -1,7 +1,6 @@
 // Copyright (c) 2011, 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.
-// Check that FallThroughError is thrown if switch clause does not terminate.
 
 import "package:expect/expect.dart";
 
@@ -16,10 +15,10 @@ String test(int n) {
 // [analyzer] COMPILE_TIME_ERROR.SWITCH_CASE_COMPLETES_NORMALLY
 // [cfe] Switch case may fall through to the next case.
       result = "one";
-  // fall-through, error if case is non-empty
+    // fall-through, error if case is non-empty
     case 9:
       result = "nine";
-  // No implicit FallThroughError at end of switch statement.
+    // No error at end of last switch case.
   }
   return result;
 }