[dart2js] Create child LocalState for inference of labeled statements.

This is analogous to what we do for other control flow constructs.
Without this, a `break` to the label causes the outer scope to also
appear aborted.

Fixes: #48317
Bug: https://github.com/flutter/flutter/issues/96394
Change-Id: I575a5bf96b25b49df6f15d429881e310b3b34d15
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/233446
Reviewed-by: Stephen Adams <sra@google.com>
Commit-Queue: Mayank Patke <fishythefish@google.com>

pkg/compiler/lib/src/inferrer/builder_kernel.dart

@@ -543,10 +543,13 @@ class KernelTypeGraphBuilder extends ir.Visitor<TypeInformation>
       // Loops and switches handle their own labels.
       visit(body);
     } else {
+      LocalState stateBefore = _state;
       JumpTarget jumpTarget = _localsMap.getJumpTargetForLabel(node);
       _setupBreaksAndContinues(jumpTarget);
+      _state = LocalState.childPath(stateBefore);
       visit(body);
-      _state.mergeAfterBreaks(_inferrer, _getBreaks(jumpTarget));
+      _state = stateBefore.mergeAfterBreaks(_inferrer, _getBreaks(jumpTarget),
+          keepOwnLocals: false);
       _clearBreaksAndContinues(jumpTarget);
     }
     return null;

pkg/compiler/test/inference/data/break_continue.dart

@@ -12,6 +12,8 @@ main() {
   noContinueInWhile();
   breakInIf();
   noBreakInIf();
+  breakInBlock();
+  noBreakInBlock();
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -107,7 +109,7 @@ noContinueInWhile() {
 }
 
 ////////////////////////////////////////////////////////////////////////////////
-// A break statement in a labeled statement.
+// A conditional break statement in a labeled statement.
 ////////////////////////////////////////////////////////////////////////////////
 
 /*member: _breakInIf:Union([exact=JSString], [exact=JSUInt31])*/
@@ -150,3 +152,34 @@ noBreakInIf() {
   _noBreakInIf(true);
   _noBreakInIf(false);
 }
+
+////////////////////////////////////////////////////////////////////////////////
+// An unconditional break statement in a labeled statement.
+////////////////////////////////////////////////////////////////////////////////
+
+/*member: breakInBlock:Value([exact=JSString], value: "")*/
+breakInBlock() {
+  dynamic local = 42;
+  label:
+  {
+    local = '';
+    break label;
+    local = false;
+  }
+  return local;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// The "labeled statement" above _without_ the break statement.
+////////////////////////////////////////////////////////////////////////////////
+
+/*member: noBreakInBlock:Value([exact=JSBool], value: false)*/
+noBreakInBlock() {
+  dynamic local = 42;
+  label:
+  {
+    local = '';
+    local = false;
+  }
+  return local;
+}

pkg/compiler/test/inference/data/general.dart

@@ -560,13 +560,13 @@ testDoWhile2() {
   return a;
 }
 
-/*member: testDoWhile3:[exact=JSUInt31]*/
+/*member: testDoWhile3:Value([exact=JSBool], value: false)*/
 testDoWhile3() {
   dynamic a = 42;
   do {
     a = 'foo';
     if (true) continue;
-    return 42;
+    return false;
   } while (true);
   // ignore: dead_code
   return a;

tests/web/regress/48317_test.dart

@@ -0,0 +1,18 @@
+// Copyright (c) 2022, 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:expect/expect.dart';
+
+helper(num c) => c * -1;
+
+void main() {
+  num a = 3;
+
+  label:
+  {
+    break label;
+  }
+
+  Expect.equals(-3, helper(a));
+}

tests/web_2/regress/48317_test.dart

@@ -0,0 +1,18 @@
+// Copyright (c) 2022, 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:expect/expect.dart';
+
+helper(num c) => c * -1;
+
+void main() {
+  num a = 3;
+
+  label:
+  {
+    break label;
+  }
+
+  Expect.equals(-3, helper(a));
+}