JS backend: added support for nested labels with the same name

#KT-5891 fixed

js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsScope.java

@@ -53,7 +53,6 @@ public abstract class JsScope {
     private static final Pattern FRESH_NAME_SUFFIX = Pattern.compile("[\\$_]\\d+$");
 
     public JsScope(JsScope parent, @NotNull String description, @Nullable String scopeId) {
-        assert (parent != null);
         this.scopeId = scopeId;
         this.description = description;
         this.parent = parent;
@@ -196,7 +195,7 @@ public abstract class JsScope {
      * Fresh name for "a0" should still be "a0_0".
      */
     @NotNull
-    private String getFreshIdent(@NotNull String suggestedIdent) {
+    protected String getFreshIdent(@NotNull String suggestedIdent) {
         char sep = '_';
         String baseName = suggestedIdent;
         int counter = 0;

js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/jsScopes.kt

@@ -16,18 +16,50 @@
 
 package com.google.dart.compiler.backend.js.ast
 
+import java.util.Stack
 
 public fun JsObjectScope(parent: JsScope, description: String): JsObjectScope = JsObjectScope(parent, description, null)
 
 public class JsObjectScope(parent: JsScope, description: String, scopeId: String?) : JsScope(parent, description, scopeId)
 
 public class JsFunctionScope(parent: JsScope, description: String) : JsScope(parent, description, null) {
+
+    private val labelScopes = Stack<LabelScope>()
+    private val topLabelScope: LabelScope?
+        get() = if (labelScopes.notEmpty) labelScopes.peek() else null
+
     override fun declareName(identifier: String): JsName = super.declareFreshName(identifier)
 
     override fun hasOwnName(name: String): Boolean = RESERVED_WORDS.contains(name) || super.hasOwnName(name)
 
     public fun declareNameUnsafe(identifier: String): JsName = super.declareName(identifier)
 
+    public fun enterLabel(label: String): JsName {
+        val scope = LabelScope(topLabelScope, label)
+        labelScopes.push(scope)
+        return scope.labelName
+    }
+
+    public fun exitLabel() {
+        assert(labelScopes.notEmpty) { "No scope to exit from" }
+        labelScopes.pop()
+    }
+
+    public fun findLabel(label: String): JsName? =
+            topLabelScope?.findName(label)
+
+    private inner class LabelScope(parent: LabelScope?, val ident: String) : JsScope(parent, "Label scope for $ident", null) {
+        val labelName = JsName(this@JsFunctionScope, parent?.getFreshIdent(ident) ?: ident)
+
+        override fun findOwnName(name: String): JsName? =
+                if (name == ident) labelName else null
+
+        override fun hasOwnName(name: String): Boolean =
+                name == ident
+                || name == labelName.getIdent()
+                || getParent()?.hasOwnName(name) ?: false
+    }
+
     class object {
         public val RESERVED_WORDS: Set<String> = setOf(
                 // keywords

js/js.inliner/src/org/jetbrains/k2js/inline/JsInliner.java

@@ -33,6 +33,7 @@ import static org.jetbrains.k2js.inline.clean.CleanPackage.removeUnusedFunctionD
 import static org.jetbrains.k2js.inline.clean.CleanPackage.removeUnusedLocalFunctionDeclarations;
 import static org.jetbrains.k2js.inline.util.UtilPackage.IdentitySet;
 import static org.jetbrains.k2js.inline.util.UtilPackage.collectNamedFunctions;
+import static org.jetbrains.k2js.inline.util.UtilPackage.refreshLabelNames;
 import static org.jetbrains.k2js.translate.utils.JsAstUtils.flattenStatement;
 
 public class JsInliner extends JsVisitorWithContextImpl {
@@ -97,6 +98,8 @@ public class JsInliner extends JsVisitorWithContextImpl {
     @Override
     public void endVisit(JsFunction function, JsContext context) {
         super.endVisit(function, context);
+        refreshLabelNames(getInliningContext().newNamingContext(), function);
+
         removeUnusedLocalFunctionDeclarations(function);
         processedFunctions.add(function);
 

js/js.inliner/src/org/jetbrains/k2js/inline/util/collectors/NameCollector.kt

@@ -36,11 +36,6 @@ class NameCollector(private val scope: JsScope) : RecursiveJsVisitor() {
 
     override fun visitFunction(x: JsFunction?) { }
 
-    override fun visitLabel(label: JsLabel?) {
-        super.visitLabel(label)
-        addNameIfNeeded(label)
-    }
-
     private fun addNameIfNeeded(hasName: HasName?) {
         val name = hasName?.getName()
         val ident = name?.getIdent()

js/js.inliner/src/org/jetbrains/k2js/inline/util/namingUtils.kt

@@ -27,6 +27,7 @@ import java.util.IdentityHashMap
 import kotlin.test.assertTrue
 import org.jetbrains.k2js.inline.context.NamingContext
 import org.jetbrains.k2js.inline.util.needToAlias
+import org.jetbrains.k2js.inline.util.rewriters.LabelNameRefreshingVisitor
 
 public fun aliasArgumentsIfNeeded(
         context: NamingContext,
@@ -70,4 +71,16 @@ public fun renameLocalNames(
         val freshName = context.getFreshName(name)
         context.replaceName(name, freshName.makeRef())
     }
+}
+
+public fun refreshLabelNames(
+        context: NamingContext,
+        function: JsFunction
+) {
+    val scope = function.getScope()
+    if (scope !is JsFunctionScope) throw AssertionError("JsFunction is expected to have JsFunctionScope")
+
+    val visitor = LabelNameRefreshingVisitor(context, scope)
+    visitor.accept(function.getBody())
+    context.applyRenameTo(function)
 }

js/js.inliner/src/org/jetbrains/k2js/inline/util/rewriters/LabelNameRefreshingVisitor.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2010-2014 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.k2js.inline.util.rewriters
+
+import com.google.dart.compiler.backend.js.ast.JsVisitorWithContextImpl
+import com.google.dart.compiler.backend.js.ast.JsFunctionScope
+import org.jetbrains.k2js.inline.context.NamingContext
+import com.google.dart.compiler.backend.js.ast.JsFunction
+import com.google.dart.compiler.backend.js.ast.JsContext
+import com.google.dart.compiler.backend.js.ast.JsLabel
+import com.google.dart.compiler.backend.js.ast.JsContinue
+import com.google.dart.compiler.backend.js.ast.JsBreak
+
+class LabelNameRefreshingVisitor(val context: NamingContext, val functionScope: JsFunctionScope) : JsVisitorWithContextImpl() {
+    override fun visit(x: JsFunction?, ctx: JsContext?): Boolean = false
+
+    override fun visit(x: JsLabel?, ctx: JsContext?): Boolean {
+        val labelName = x!!.getName()
+        val freshName = functionScope.enterLabel(labelName.getIdent())
+
+        if (freshName.getIdent() != labelName.getIdent()) {
+            context.replaceName(labelName, freshName.makeRef())
+        }
+
+        return super.visit(x, ctx)
+    }
+
+    override fun endVisit(x: JsLabel?, ctx: JsContext?) {
+        super.endVisit(x, ctx)
+        functionScope.exitLabel()
+    }
+}

js/js.translator/src/org/jetbrains/k2js/translate/expression/ExpressionVisitor.java

@@ -293,9 +293,12 @@ public final class ExpressionVisitor extends TranslatorVisitor<JsNode> {
         assert baseExpression != null;
         JsScope scope = context.scope();
         assert scope instanceof JsFunctionScope: "Labeled statement is unexpected outside of function scope";
-        JsName name = ((JsFunctionScope) scope).declareNameUnsafe(getReferencedName(expression.getTargetLabel()));
+        JsFunctionScope functionScope = (JsFunctionScope) scope;
+        String labelIdent = getReferencedName(expression.getTargetLabel());
+        JsName labelName = functionScope.enterLabel(labelIdent);
         JsStatement baseStatement = Translation.translateAsStatement(baseExpression, context);
-        return new JsLabel(name, baseStatement).source(expression);
+        functionScope.exitLabel();
+        return new JsLabel(labelName, baseStatement).source(expression);
     }
 
     @Override
@@ -369,11 +372,13 @@ public final class ExpressionVisitor extends TranslatorVisitor<JsNode> {
         if (labelElement == null) {
             return null;
         }
-        else {
+
-            JsName name = context.scope().findName(getReferencedName(labelElement));
+        String labelIdent = getReferencedName(labelElement);
-            assert name != null;
+        JsScope scope = context.scope();
-            return name.makeRef();
+        assert scope instanceof JsFunctionScope: "Labeled statement is unexpected outside of function scope";
-        }
+        JsName labelName = ((JsFunctionScope) scope).findLabel(labelIdent);
+        assert labelName != null;
+        return labelName.makeRef();
     }
 
     @Override