Renames Es7ToEs6Converter to Es7RewriteExponentialOperator and si…

…mplifies its implementation to support adding type to the synthesized AST.

This rename was done because the exponential operator is the only thing this class ever handled, and we don't actually want it to do anything else.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=198788507

src/com/google/javascript/jscomp/Es7RewriteExponentialOperator.java

@@ -0,0 +1,127 @@
+/*
+ * Copyright 2014 The Closure Compiler Authors.
+ *
+ * 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 com.google.javascript.jscomp;
+
+import com.google.javascript.jscomp.parsing.parser.FeatureSet;
+import com.google.javascript.jscomp.parsing.parser.FeatureSet.Feature;
+import com.google.javascript.rhino.IR;
+import com.google.javascript.rhino.Node;
+import com.google.javascript.rhino.jstype.JSType;
+import com.google.javascript.rhino.jstype.JSTypeNative;
+import com.google.javascript.rhino.jstype.JSTypeRegistry;
+
+/** Replaces the ES7 `**` and `**=` operators to calls to `Math.pow`. */
+public final class Es7RewriteExponentialOperator
+    implements NodeTraversal.Callback, HotSwapCompilerPass {
+
+  private static final FeatureSet transpiledFeatures =
+      FeatureSet.BARE_MINIMUM.with(Feature.EXPONENT_OP);
+
+  private final AbstractCompiler compiler;
+  private final Node mathPowCall; // This node should only ever be cloned, not directly inserted.
+
+  private final JSType numberType;
+  private final JSType stringType;
+  private final JSType mathType;
+  private final JSType mathPowType;
+
+  public Es7RewriteExponentialOperator(AbstractCompiler compiler) {
+    this.compiler = compiler;
+
+    if (compiler.hasTypeCheckingRun()) {
+      JSTypeRegistry registry = compiler.getTypeRegistry();
+      this.numberType = registry.getNativeType(JSTypeNative.NUMBER_TYPE);
+      this.stringType = registry.getNativeType(JSTypeNative.STRING_TYPE);
+      // TODO(nickreid): Get the actual type of the `Math` object here in case optimizations care.
+      this.mathType = registry.getNativeType(JSTypeNative.UNKNOWN_TYPE);
+      this.mathPowType = registry.createFunctionType(numberType, numberType, numberType);
+    } else {
+      this.numberType = null;
+      this.stringType = null;
+      this.mathType = null;
+      this.mathPowType = null;
+    }
+
+    this.mathPowCall = createMathPowCall();
+  }
+
+  @Override
+  public void process(Node externs, Node root) {
+    TranspilationPasses.processTranspile(compiler, externs, transpiledFeatures, this);
+    TranspilationPasses.processTranspile(compiler, root, transpiledFeatures, this);
+    TranspilationPasses.markFeaturesAsTranspiledAway(compiler, transpiledFeatures);
+  }
+
+  @Override
+  public void hotSwapScript(Node scriptRoot, Node originalRoot) {
+    TranspilationPasses.hotSwapTranspile(compiler, scriptRoot, transpiledFeatures, this);
+    TranspilationPasses.markFeaturesAsTranspiledAway(compiler, transpiledFeatures);
+  }
+
+  @Override
+  public boolean shouldTraverse(NodeTraversal t, Node n, Node parent) {
+    return true;
+  }
+
+  @Override
+  public void visit(NodeTraversal t, Node n, Node parent) {
+    switch (n.getToken()) {
+      case EXPONENT:
+        visitExponentiationOperator(n);
+        break;
+      case ASSIGN_EXPONENT:
+        visitExponentiationAssignmentOperator(n);
+        break;
+      default:
+        break;
+    }
+  }
+
+  private void visitExponentiationOperator(Node operator) {
+    Node callClone = mathPowCall.cloneTree();
+    callClone.addChildToBack(operator.removeFirstChild()); // Base argument.
+    callClone.addChildToBack(operator.removeFirstChild()); // Exponent argument.
+
+    callClone.useSourceInfoIfMissingFromForTree(operator);
+    operator.replaceWith(callClone);
+
+    compiler.reportChangeToEnclosingScope(callClone);
+  }
+
+  private void visitExponentiationAssignmentOperator(Node operator) {
+    Node lValue = operator.removeFirstChild();
+
+    Node callClone = mathPowCall.cloneTree();
+    callClone.addChildToBack(lValue.cloneTree()); // Base argument.
+    callClone.addChildToBack(operator.removeFirstChild()); // Exponent argument.
+
+    Node assignment = IR.assign(lValue, callClone).setJSType(numberType);
+
+    assignment.useSourceInfoIfMissingFromForTree(operator);
+    operator.replaceWith(assignment);
+
+    compiler.reportChangeToEnclosingScope(assignment);
+  }
+
+  private Node createMathPowCall() {
+    return IR.call(
+            IR.getprop(
+                    IR.name("Math").setJSType(mathType), // Force wrapping.
+                    IR.string("pow").setJSType(stringType))
+                .setJSType(mathPowType))
+        .setJSType(numberType);
+  }
+}

src/com/google/javascript/jscomp/TranspilationPasses.java

@@ -156,7 +156,7 @@ protected FeatureSet featureSet() {
       new HotSwapPassFactory("convertEs7ToEs6") {
         @Override
         protected HotSwapCompilerPass create(final AbstractCompiler compiler) {
-          return new Es7ToEs6Converter(compiler);
+          return new Es7RewriteExponentialOperator(compiler);
         }
 
         @Override

test/com/google/javascript/jscomp/Es7ToEs6ConverterTest.java → test/com/google/javascript/jscomp/Es7RewriteExponentialOperatorTest.java

@@ -21,9 +21,9 @@
  * Test cases for ES6 transpilation. Despite the name, this isn't just testing {@link
  * Es6ToEs3Converter}, but also some other ES6 transpilation passes. See #getProcessor.
  */
-public final class Es7ToEs6ConverterTest extends CompilerTestCase {
+public final class Es7RewriteExponentialOperatorTest extends CompilerTestCase {
 
-  public Es7ToEs6ConverterTest() {
+  public Es7RewriteExponentialOperatorTest() {
     super(MINIMAL_EXTERNS);
   }
 
@@ -37,7 +37,7 @@ protected void setUp() throws Exception {
 
   @Override
   protected CompilerPass getProcessor(Compiler compiler) {
-    return new Es7ToEs6Converter(compiler);
+    return new Es7RewriteExponentialOperator(compiler);
   }
 
   @Override