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 <mit@google.com>
Commit-Queue: Lasse Nielsen <lrn@google.com>
Auto-Submit: Lasse Nielsen <lrn@google.com>
Reviewed-by: Brian Quinlan <bquinlan@google.com>

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

@@ -1,38 +0,0 @@
-// TODO(multitest): This was automatically migrated from a multitest and may
-// contain strange or dead code.
-
-// 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.
-
-// VMOptions=
-// VMOptions=--force-switch-dispatch-type=0
-// VMOptions=--force-switch-dispatch-type=1
-// VMOptions=--force-switch-dispatch-type=2
-
-import "package:expect/expect.dart";
-
-String test(int n) {
-  String result = "foo";
-  switch (n) {
-    case 0:
-      result = "zero";
-      break;
-    case 1:
-
-  // fall-through, error if case is non-empty
-    case 9:
-      result = "nine";
-  // No implicit FallThroughError at end of switch statement.
-  }
-  return result;
-}
-
-main() {
-  Expect.equals("zero", test(0));
-  Expect.equals("nine", test(1));
-  Expect.equals("nine", test(9));
-  Expect.equals("foo", test(99));
-}

tests/language/switch/fallthru_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;
 }

tests/language_2/switch/empty_block_case_test.dart

@@ -15,18 +15,12 @@ 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_2/switch/fallthru_runtime_test.dart

@@ -1,39 +0,0 @@
-// TODO(multitest): This was automatically migrated from a multitest and may
-// contain strange or dead code.
-
-// @dart = 2.9
-
-// 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.
-
-// VMOptions=
-// VMOptions=--force-switch-dispatch-type=0
-// VMOptions=--force-switch-dispatch-type=1
-// VMOptions=--force-switch-dispatch-type=2
-
-import "package:expect/expect.dart";
-
-String test(int n) {
-  String result = "foo";
-  switch (n) {
-    case 0:
-      result = "zero";
-      break;
-    case 1:
-
-  // fall-through, error if case is non-empty
-    case 9:
-      result = "nine";
-  // No implicit FallThroughError at end of switch statement.
-  }
-  return result;
-}
-
-main() {
-  Expect.equals("zero", test(0));
-  Expect.equals("nine", test(1));
-  Expect.equals("nine", test(9));
-  Expect.equals("foo", test(99));
-}

tests/language_2/switch/fallthru_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.
 
 // @dart = 2.9
 
@@ -18,10 +17,10 @@ String test(int n) {
 // [analyzer] COMPILE_TIME_ERROR.CASE_BLOCK_NOT_TERMINATED
 // [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;
 }