JS: make JsEmpty singleton

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

@@ -4,7 +4,7 @@
 
 package com.google.dart.compiler.backend.js.ast
 
-public class JsEmpty : SourceInfoAwareJsNode(), JsStatement {
+public object JsEmpty : SourceInfoAwareJsNode(), JsStatement {
 
     override fun accept(v: JsVisitor) {
         v.visitEmpty(this)

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

@@ -26,7 +26,7 @@ public class JsEmptyExpression extends JsExpressionImpl {
     @Override
     @NotNull
     public JsStatement makeStmt() {
-        return new JsEmpty();
+        return JsEmpty.INSTANCE$;
     }
 
     @Override

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

@@ -18,8 +18,6 @@ import static com.google.dart.compiler.backend.js.ast.JsNumberLiteral.JsIntLiter
  * A JavaScript program.
  */
 public final class JsProgram extends SourceInfoAwareJsNode {
-    @NotNull
-    private final JsEmpty emptyStatement;
     @NotNull final JsExpression emptyExpression;
 
     private JsProgramFragment[] fragments;
@@ -36,15 +34,9 @@ public final class JsProgram extends SourceInfoAwareJsNode {
         topScope = new JsObjectScope(rootScope, "Global", unitId);
         setFragmentCount(1);
 
-        emptyStatement = new JsEmpty();
         emptyExpression = new JsEmptyExpression();
     }
 
-    @NotNull
-    public JsEmpty getEmptyStatement() {
-        return emptyStatement;
-    }
-
     @NotNull
     public JsExpression getEmptyExpression() {
         return emptyExpression;

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

@@ -283,12 +283,6 @@ public class JsInliner extends JsVisitorWithContextImpl {
                     return getLastStatementLevelContext();
                 }
 
-                @NotNull
-                @Override
-                protected JsStatement getEmptyStatement() {
-                    return getFunctionContext().getEmpty();
-                }
-
                 @Override
                 public void shiftCurrentStatementForward() {
                     super.shiftCurrentStatementForward();

js/js.inliner/src/org/jetbrains/kotlin/js/inline/context/FunctionContext.kt

@@ -52,10 +52,6 @@ abstract class FunctionContext(
         return getFunctionDefinitionImpl(call) != null
     }
 
-    public fun getEmpty(): JsEmpty {
-        return getScope().getProgram()?.getEmptyStatement()!!
-    }
-
     public fun getScope(): JsScope {
         return function.getScope()
     }

js/js.inliner/src/org/jetbrains/kotlin/js/inline/context/StatementContext.kt

@@ -17,6 +17,7 @@
 package org.jetbrains.kotlin.js.inline.context
 
 import com.google.dart.compiler.backend.js.ast.JsContext
+import com.google.dart.compiler.backend.js.ast.JsEmpty
 import com.google.dart.compiler.backend.js.ast.JsStatement
 
 abstract class StatementContext {
@@ -28,20 +29,18 @@ abstract class StatementContext {
 
     public fun removeCurrentStatement() {
         val statementContext = getCurrentStatementContext()
-        statementContext.replaceMe(getEmptyStatement())
+        statementContext.replaceMe(JsEmpty)
     }
 
     open public fun shiftCurrentStatementForward() {
         val statementContext = getCurrentStatementContext()
         val currentStatement = getCurrentStatement()
         statementContext.insertAfter(currentStatement)
-        statementContext.replaceMe(getEmptyStatement())
+        statementContext.replaceMe(JsEmpty)
     }
 
     public fun getCurrentStatement(): JsStatement {
         val statementContext = getCurrentStatementContext()
         return statementContext.getCurrentNode() as JsStatement
     }
-
-    protected abstract fun getEmptyStatement(): JsStatement
 }

js/js.parser/src/com/google/gwt/dev/js/JsAstMapper.java

@@ -517,7 +517,7 @@ public class JsAstMapper {
                 toForIn.setBody(bodyStmt);
             }
             else {
-                toForIn.setBody(program.getEmptyStatement());
+                toForIn.setBody(JsEmpty.INSTANCE$);
             }
 
             return toForIn;
@@ -545,7 +545,7 @@ public class JsAstMapper {
                 toFor.setBody(bodyStmt);
             }
             else {
-                toFor.setBody(program.getEmptyStatement());
+                toFor.setBody(JsEmpty.INSTANCE$);
             }
             return toFor;
         }
@@ -892,7 +892,7 @@ public class JsAstMapper {
         else {
             // When map() returns null, we return an empty statement.
             //
-            return program.getEmptyStatement();
+            return JsEmpty.INSTANCE$;
         }
     }
 

js/js.translator/src/org/jetbrains/kotlin/js/translate/context/TranslationContext.java

@@ -302,11 +302,6 @@ public class TranslationContext {
         return dynamicContext.jsBlock();
     }
 
-    @NotNull
-    public JsEmpty getEmptyStatement() {
-        return program().getEmptyStatement();
-    }
-
     @NotNull
     public JsExpression getEmptyExpression() {
         return program().getEmptyExpression();

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

@@ -154,7 +154,7 @@ public final class ExpressionVisitor extends TranslatorVisitor<JsNode> {
         if (expressionInside != null) {
             return Translation.translateExpression(expressionInside, context);
         }
-        return context.getEmptyStatement();
+        return JsEmpty.INSTANCE$;
     }
 
     @Override

js/js.translator/src/org/jetbrains/kotlin/js/translate/expression/LoopTranslator.kt

@@ -45,7 +45,7 @@ public fun createWhile(doWhile: Boolean, expression: JetWhileExpressionBase, con
         if (body != null)
             Translation.translateAsStatementAndMergeInBlockIfNeeded(body, context)
         else
-            context.getEmptyStatement()
+            JsEmpty
 
     if (!conditionBlock.isEmpty()) {
         val breakIfConditionIsFalseStatement = JsIf(not(jsCondition), JsBreak())

js/js.translator/src/org/jetbrains/kotlin/js/translate/expression/WhenTranslator.java

@@ -63,7 +63,7 @@ public final class WhenTranslator extends AbstractTranslator {
 
     private JsStatement translate() {
         if (expressionToMatch != null && JsAstUtils.isEmptyExpression(expressionToMatch)) {
-            return context().getEmptyStatement();
+            return JsEmpty.INSTANCE$;
         }
 
         JsIf currentIf = null;