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/*
* Copyright 2015 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 static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkState;
import static com.google.javascript.jscomp.DiagnosticType.error;
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.JSDocInfo;
import com.google.javascript.rhino.JSDocInfoBuilder;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;
import com.google.javascript.rhino.jstype.JSType;
import com.google.javascript.rhino.jstype.JSTypeNative;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.Iterator;
/**
* Rewrites destructuring patterns and default parameters to valid ES3 code or to a different form
* of destructuring.
*/
public final class Es6RewriteDestructuring implements NodeTraversal.Callback, HotSwapCompilerPass {
public static final DiagnosticType UNEXPECTED_DESTRUCTURING_REST_PARAMETER =
error(
"JSC_UNEXPECTED_DESTRUCTURING_REST_PARAMETER",
"Es6RewriteDestructuring not expecting object pattern rest parameter");
enum ObjectDestructuringRewriteMode {
/**
* Rewrite all object destructuring patterns. This is the default mode used if no
* ObjectDestructuringRewriteMode is provided to the Builder.
*
* Used to transpile ES2018 -> ES5
*/
REWRITE_ALL_OBJECT_PATTERNS,
/**
* Rewrite only destructuring patterns that contain object pattern rest properties (whether the
* rest is on the top level or nested within a property).
*
*
Used to transpile ES2018 -> ES2017
*/
REWRITE_OBJECT_REST,
}
private final AbstractCompiler compiler;
private final ObjectDestructuringRewriteMode rewriteMode;
private final AstFactory astFactory;
private final FeatureSet featuresToTriggerRunningPass;
private final FeatureSet featuresToMarkAsRemoved;
private final Deque patternNestingStack = new ArrayDeque<>();
static final String DESTRUCTURING_TEMP_VAR = "$jscomp$destructuring$var";
private int destructuringVarCounter = 0;
private Es6RewriteDestructuring(Builder builder) {
this.compiler = builder.compiler;
this.rewriteMode = builder.rewriteMode;
this.astFactory = compiler.createAstFactory();
switch (this.rewriteMode) {
case REWRITE_ALL_OBJECT_PATTERNS:
this.featuresToTriggerRunningPass =
FeatureSet.BARE_MINIMUM.with(
Feature.DEFAULT_PARAMETERS,
Feature.ARRAY_DESTRUCTURING,
Feature.ARRAY_PATTERN_REST,
Feature.OBJECT_DESTRUCTURING);
// If OBJECT_PATTERN_REST were to be present in featuresToTriggerRunningPass and not the
// input language featureSet (such as ES6=>ES5) the pass would be skipped.
this.featuresToMarkAsRemoved =
featuresToTriggerRunningPass.with(Feature.OBJECT_PATTERN_REST);
break;
case REWRITE_OBJECT_REST:
// TODO(bradfordcsmith): We shouldn't really need to remove default parameters for this
// case.
this.featuresToTriggerRunningPass =
FeatureSet.BARE_MINIMUM.with(Feature.OBJECT_PATTERN_REST);
this.featuresToMarkAsRemoved = this.featuresToTriggerRunningPass;
break;
default:
throw new AssertionError(
"Es6RewriteDestructuring cannot handle ObjectDestructuringRewriteMode "
+ this.rewriteMode);
}
}
static class Builder {
private final AbstractCompiler compiler;
private ObjectDestructuringRewriteMode rewriteMode =
ObjectDestructuringRewriteMode.REWRITE_ALL_OBJECT_PATTERNS;
public Builder(AbstractCompiler compiler) {
this.compiler = compiler;
}
public Builder setDestructuringRewriteMode(ObjectDestructuringRewriteMode rewriteMode) {
this.rewriteMode = rewriteMode;
return this;
}
public Es6RewriteDestructuring build() {
return new Es6RewriteDestructuring(this);
}
}
private static final class PatternNestingLevel {
final Node pattern;
boolean hasNestedObjectRest;
public PatternNestingLevel(Node pattern, boolean hasNestedRest) {
this.pattern = pattern;
this.hasNestedObjectRest = hasNestedRest;
}
}
@Override
public void process(Node externs, Node root) {
checkState(patternNestingStack.isEmpty());
TranspilationPasses.processTranspile(compiler, externs, featuresToTriggerRunningPass, this);
TranspilationPasses.processTranspile(compiler, root, featuresToTriggerRunningPass, this);
TranspilationPasses.maybeMarkFeaturesAsTranspiledAway(compiler, featuresToMarkAsRemoved);
checkState(patternNestingStack.isEmpty());
}
@Override
public void hotSwapScript(Node scriptRoot, Node originalRoot) {
checkState(patternNestingStack.isEmpty());
TranspilationPasses.hotSwapTranspile(compiler, scriptRoot, featuresToTriggerRunningPass, this);
TranspilationPasses.maybeMarkFeaturesAsTranspiledAway(compiler, featuresToMarkAsRemoved);
checkState(patternNestingStack.isEmpty());
}
@Override
public boolean shouldTraverse(NodeTraversal t, Node n, Node parent) {
switch (n.getToken()) {
case FUNCTION:
ensureArrowFunctionsHaveBlockBodies(t, n);
break;
case PARAM_LIST:
pullDestructuringOutOfParams(n, parent);
break;
case ARRAY_PATTERN:
case OBJECT_PATTERN:
{
boolean hasRest = n.isObjectPattern() && n.hasChildren() && n.getLastChild().isRest();
if (!this.patternNestingStack.isEmpty() && hasRest) {
for (PatternNestingLevel level : patternNestingStack) {
if (level.hasNestedObjectRest) {
break;
}
level.hasNestedObjectRest = true;
}
this.patternNestingStack.peekLast().hasNestedObjectRest = true;
}
this.patternNestingStack.addLast(new PatternNestingLevel(n, hasRest));
break;
}
default:
break;
}
return true;
}
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
if (parent != null && parent.isDestructuringLhs()) {
parent = parent.getParent();
}
switch (n.getToken()) {
case ARRAY_PATTERN:
case OBJECT_PATTERN:
visitPattern(t, n, parent);
if (n == this.patternNestingStack.getLast().pattern) {
this.patternNestingStack.removeLast();
}
break;
default:
break;
}
}
/**
* If the function is an arrow function, wrap the body in a block if it is not already a block.
*/
// TODO(bradfordcsmith): This should be separated from this pass.
private void ensureArrowFunctionsHaveBlockBodies(NodeTraversal t, Node function) {
Node body = function.getLastChild();
if (!body.isBlock()) {
body.detach();
Node replacement = IR.block(IR.returnNode(body)).useSourceInfoIfMissingFromForTree(body);
function.addChildToBack(replacement);
t.reportCodeChange();
}
}
/** Pulls all default and destructuring parameters out of function parameters. */
// TODO(bradfordcsmith): Ideally if we're only removing OBJECT_REST, we should only do this when
// the parameter list contains a usage of OBJECT_REST.
private void pullDestructuringOutOfParams(Node paramList, Node function) {
Node insertSpot = null;
Node body = function.getLastChild();
Node next = null;
for (Node param = paramList.getFirstChild(); param != null; param = next) {
next = param.getNext();
if (param.isDefaultValue()) {
Node nameOrPattern = param.removeFirstChild();
// We'll be cloning nameOrPattern below, and we don't want to clone the JSDoc info with it
JSDocInfo jsDoc = nameOrPattern.getJSDocInfo();
nameOrPattern.setJSDocInfo(null);
Node defaultValue = param.removeFirstChild();
Node newParam;
// Treat name=undefined (and equivalent) as if it was just name. There
// is no need to generate a (name===void 0?void 0:name) statement for
// such arguments.
boolean isNoop = false;
if (!nameOrPattern.isName()) {
// Do not try to optimize unless nameOrPattern is a simple name.
} else if (defaultValue.isName()) {
isNoop = "undefined".equals(defaultValue.getString());
} else if (defaultValue.isVoid()) {
// Any kind of 'void literal' is fine, but 'void fun()' or anything
// else with side effects isn't. We're not trying to be particularly
// smart here and treat 'void {}' for example as if it could cause side effects.
isNoop = NodeUtil.isImmutableValue(defaultValue.getFirstChild());
}
if (isNoop) {
newParam = nameOrPattern.cloneTree();
} else {
newParam =
nameOrPattern.isName()
? nameOrPattern
: astFactory.createName(getTempVariableName(), nameOrPattern.getJSType());
Node lhs = nameOrPattern.cloneTree();
Node rhs = defaultValueHook(newParam.cloneTree(), defaultValue);
Node newStatement =
nameOrPattern.isName()
? IR.exprResult(astFactory.createAssign(lhs, rhs))
: IR.var(lhs, rhs);
newStatement.useSourceInfoIfMissingFromForTree(param);
body.addChildAfter(newStatement, insertSpot);
insertSpot = newStatement;
}
paramList.replaceChild(param, newParam);
newParam.setOptionalArg(true);
newParam.setJSDocInfo(jsDoc);
compiler.reportChangeToChangeScope(function);
} else if (param.isDestructuringPattern()) {
insertSpot =
replacePatternParamWithTempVar(function, insertSpot, param, getTempVariableName());
compiler.reportChangeToChangeScope(function);
} else if (param.isRest() && param.getFirstChild().isDestructuringPattern()) {
insertSpot =
replacePatternParamWithTempVar(
function, insertSpot, param.getFirstChild(), getTempVariableName());
compiler.reportChangeToChangeScope(function);
}
}
}
/**
* Replace a destructuring pattern parameter with a a temporary parameter name and add a new
* local variable declaration to the function assigning the temporary parameter to the pattern.
*
* Note: Rewrites of variable declaration destructuring will happen later to rewrite
* this declaration as non-destructured code.
* @param function
* @param insertSpot The local variable declaration will be inserted after this statement.
* @param patternParam
* @param tempVarName the name to use for the temporary variable
* @return the declaration statement that was generated for the local variable
*/
private Node replacePatternParamWithTempVar(
Node function, Node insertSpot, Node patternParam, String tempVarName) {
// Convert `function f([a, b]) {}` to `function f(tempVar) { var [a, b] = tempVar; }`
JSType paramType = patternParam.getJSType();
Node newParam = astFactory.createName(tempVarName, paramType);
newParam.setJSDocInfo(patternParam.getJSDocInfo());
patternParam.replaceWith(newParam);
Node newDecl = IR.var(patternParam, astFactory.createName(tempVarName, paramType));
function.getLastChild().addChildAfter(newDecl, insertSpot);
return newDecl;
}
/** Creates a new unique name to use for a pattern we need to rewrite. */
private String getTempVariableName() {
return DESTRUCTURING_TEMP_VAR + (destructuringVarCounter++);
}
private void visitPattern(NodeTraversal t, Node pattern, Node parent) {
if (NodeUtil.isNameDeclaration(parent) && !NodeUtil.isEnhancedFor(parent.getParent())) {
replacePattern(t, pattern, pattern.getNext(), parent, parent);
} else if (parent.isAssign()) {
if (parent.getParent().isExprResult()) {
replacePattern(t, pattern, pattern.getNext(), parent, parent.getParent());
} else {
wrapAssignmentInCallToArrow(t, parent);
}
} else if (parent.isRest()
|| parent.isStringKey()
|| parent.isArrayPattern()
|| parent.isDefaultValue()
|| parent.isComputedProp()) {
// Nested pattern; do nothing. We will visit it after rewriting the parent.
} else if (NodeUtil.isEnhancedFor(parent) || NodeUtil.isEnhancedFor(parent.getParent())) {
visitDestructuringPatternInEnhancedFor(pattern);
} else if (parent.isCatch()) {
visitDestructuringPatternInCatch(t, pattern);
} else {
throw new IllegalStateException("unexpected parent");
}
}
/**
* Transpiles a destructuring pattern in a declaration or assignment to ES5
*
* @param nodeToDetach a statement node containing the pattern. This method will replace the node
* with one or more other statements.
*/
private void replacePattern(
NodeTraversal t, Node pattern, Node rhs, Node parent, Node nodeToDetach) {
checkArgument(NodeUtil.isStatement(nodeToDetach), nodeToDetach);
switch (pattern.getToken()) {
case ARRAY_PATTERN:
replaceArrayPattern(t, pattern, rhs, parent, nodeToDetach);
break;
case OBJECT_PATTERN:
replaceObjectPattern(t, pattern, rhs, parent, nodeToDetach);
break;
default:
throw new IllegalStateException("unexpected");
}
}
/**
* Convert 'var {a: b, c: d} = rhs' to:
*
* @const var temp = rhs; var b = temp.a; var d = temp.c;
*/
private void replaceObjectPattern(
NodeTraversal t, Node objectPattern, Node rhs, Node parent, Node nodeToDetach) {
final Scope scope = t.getScope(); // get scope here, AST may be in temporary invalid state later
String tempVarName = getTempVariableName();
final JSType tempVarType = objectPattern.getJSType();
String restTempVarName = null;
// If the last child is a rest node we will want a list of the stated properties so we can
// exclude them from being written to the rest variable.
ArrayList propsToDeleteForRest = null;
if (objectPattern.hasChildren() && objectPattern.getLastChild().isRest()) {
propsToDeleteForRest = new ArrayList<>();
restTempVarName = getTempVariableName();
} else if (rewriteMode == ObjectDestructuringRewriteMode.REWRITE_OBJECT_REST) {
// We are configured to only break object pattern rest, but this destructure has none.
if (!this.patternNestingStack.peekLast().hasNestedObjectRest) {
// Replacement is performed after the post-order visit has reached the root pattern node, so
// peeking last represents if there is a rest property anywhere in the entire pattern. All
// nesting levels of lower levels have already been popped.
destructuringVarCounter--;
return;
}
}
// create the declaration `var temp = rhs;`
Node tempDecl =
IR.var(astFactory.createName(tempVarName, tempVarType), rhs.detach())
.useSourceInfoIfMissingFromForTree(objectPattern);
// TODO(tbreisacher): Remove the "if" and add this JSDoc unconditionally.
if (parent.isConst()) {
JSDocInfoBuilder jsDoc = new JSDocInfoBuilder(false);
jsDoc.recordConstancy();
tempDecl.setJSDocInfo(jsDoc.build());
}
nodeToDetach.getParent().addChildBefore(tempDecl, nodeToDetach);
for (Node child = objectPattern.getFirstChild(), next; child != null; child = next) {
next = child.getNext();
final Node newLHS;
final Node newRHS;
if (child.isStringKey()) {
// const {a: b} = obj;
Node tempVarNameNode = astFactory.createName(tempVarName, tempVarType);
Node getprop =
child.isQuotedString()
? astFactory.createGetElem(
tempVarNameNode, astFactory.createString(child.getString()))
: astFactory.createGetProp(tempVarNameNode, child.getString());
Node value = child.removeFirstChild();
if (!value.isDefaultValue()) {
newLHS = value;
newRHS = getprop;
} else {
newLHS = value.removeFirstChild();
Node defaultValue = value.removeFirstChild();
newRHS = defaultValueHook(getprop, defaultValue);
}
if (propsToDeleteForRest != null) {
propsToDeleteForRest.add(child);
}
} else if (child.isComputedProp()) {
// const {[propExpr]: newLHS = defaultValue} = newRHS;
boolean hasDefault = child.getLastChild().isDefaultValue();
final Node defaultValue;
Node propExpr = child.removeFirstChild();
if (hasDefault) {
Node defaultNode = child.getLastChild();
newLHS = defaultNode.removeFirstChild();
defaultValue = defaultNode.removeFirstChild();
} else {
newLHS = child.removeFirstChild();
defaultValue = null;
}
if (propsToDeleteForRest != null) {
// A "...rest" variable is present and result of computation must be cached
String exprEvalTempVarName = getTempVariableName();
Node exprEvalTempVarModel =
astFactory.createName(exprEvalTempVarName, propExpr.getJSType()); // clone this node
Node exprEvalDecl = IR.var(exprEvalTempVarModel.cloneNode(), propExpr);
exprEvalDecl.useSourceInfoIfMissingFromForTree(child);
nodeToDetach.getParent().addChildBefore(exprEvalDecl, nodeToDetach);
propExpr = exprEvalTempVarModel.cloneNode();
propsToDeleteForRest.add(exprEvalTempVarModel.cloneNode());
}
if (hasDefault) {
// tempVarName[propExpr]
Node getelem =
astFactory.createGetElem(astFactory.createName(tempVarName, tempVarType), propExpr);
// var tempVarName2 = tempVarName1[propExpr]
String intermediateTempVarName = getTempVariableName();
Node intermediateDecl =
IR.var(astFactory.createName(intermediateTempVarName, getelem.getJSType()), getelem);
intermediateDecl.useSourceInfoIfMissingFromForTree(child);
nodeToDetach.getParent().addChildBefore(intermediateDecl, nodeToDetach);
// tempVarName2 === undefined ? defaultValue : tempVarName2
newRHS =
defaultValueHook(
astFactory.createName(intermediateTempVarName, getelem.getJSType()),
defaultValue);
} else {
newRHS =
astFactory.createGetElem(
astFactory.createName(tempVarName, newLHS.getJSType()), propExpr);
}
} else if (child.isRest()) {
if (next != null) {
throw new IllegalStateException("object rest may not be followed by any properties");
}
// TODO(b/116532470): see if casting this to a more specific type fixes disambiguation
Node assignCall = astFactory.createCall(astFactory.createQName(scope, "Object.assign"));
assignCall.addChildToBack(astFactory.createObjectLit());
assignCall.addChildToBack(astFactory.createName(tempVarName, tempVarType));
Node restTempDecl = IR.var(astFactory.createName(restTempVarName, tempVarType), assignCall);
restTempDecl.useSourceInfoIfMissingFromForTree(objectPattern);
nodeToDetach.getParent().addChildAfter(restTempDecl, tempDecl);
Node restName = child.getOnlyChild(); // e.g. get `rest` from `const {...rest} = {};`
newLHS = astFactory.createName(restName.getString(), restName.getJSType());
newRHS = objectPatternRestRHS(objectPattern, child, restTempVarName, propsToDeleteForRest);
} else {
throw new IllegalStateException("unexpected child");
}
Node newNode;
if (NodeUtil.isNameDeclaration(parent)) {
newNode = IR.declaration(newLHS, newRHS, parent.getToken());
} else if (parent.isAssign()) {
newNode = IR.exprResult(astFactory.createAssign(newLHS, newRHS));
} else {
throw new IllegalStateException("not reached");
}
newNode.useSourceInfoIfMissingFromForTree(child);
nodeToDetach.getParent().addChildBefore(newNode, nodeToDetach);
// Explicitly visit the LHS of the new node since it may be a nested
// destructuring pattern.
visit(t, newLHS, newLHS.getParent());
}
nodeToDetach.detach();
t.reportCodeChange();
}
/**
* Convert "rest" of object destructuring lhs by making a clone and deleting any properties that
* were stated in the original object pattern.
*
* Nodes in statedProperties that are a stringKey will be used in a getprop when deleting. All
* other types will be used in a getelem such as what is done for computed properties.
*
*
* {a, [foo()]:b, ...x} = rhs;
* becomes
* var temp = rhs;
* var temp1 = Object.assign({}, temp);
* var temp2 = foo()
* a = temp.a
* b = temp[foo()]
* x = (delete temp1.a, delete temp1[temp2], temp1);
*
*
* @param rest node representing the "...rest" of objectPattern
* @param restTempVarName name of var containing clone of result of rhs evaluation
* @param statedProperties list of properties to delete from the clone
*/
private Node objectPatternRestRHS(
Node objectPattern, Node rest, String restTempVarName, ArrayList statedProperties) {
checkArgument(objectPattern.getLastChild() == rest);
Node restTempVarModel = astFactory.createName(restTempVarName, objectPattern.getJSType());
Node result = restTempVarModel.cloneNode();
if (!statedProperties.isEmpty()) {
Iterator propItr = statedProperties.iterator();
Node comma = deletionNodeForRestProperty(restTempVarModel.cloneNode(), propItr.next());
while (propItr.hasNext()) {
comma =
astFactory.createComma(
comma, deletionNodeForRestProperty(restTempVarModel.cloneNode(), propItr.next()));
}
result = astFactory.createComma(comma, result);
}
result.useSourceInfoIfMissingFromForTree(rest);
return result;
}
private Node deletionNodeForRestProperty(Node restTempVarNameNode, Node property) {
final Node get;
switch (property.getToken()) {
case STRING_KEY:
get =
property.isQuotedString()
? astFactory.createGetElem(
restTempVarNameNode, astFactory.createString(property.getString()))
: astFactory.createGetProp(restTempVarNameNode, property.getString());
break;
case NAME:
get = astFactory.createGetElem(restTempVarNameNode, property);
break;
default:
throw new IllegalStateException(
"Unexpected property to delete node: " + property.toStringTree());
}
return astFactory.createDelProp(get);
}
/**
* Convert var [x, y] = rhs to:
*
* var temp = $jscomp.makeIterator(rhs);
* var x = temp.next().value;
* var y = temp.next().value;
*
*/
private void replaceArrayPattern(
NodeTraversal t, Node arrayPattern, Node rhs, Node parent, Node nodeToDetach) {
if (rewriteMode == ObjectDestructuringRewriteMode.REWRITE_OBJECT_REST) {
if (patternNestingStack.isEmpty() || !patternNestingStack.peekLast().hasNestedObjectRest) {
return;
}
}
String tempVarName = getTempVariableName();
Node makeIteratorCall = astFactory.createJSCompMakeIteratorCall(rhs.detach(), t.getScope());
Node tempVarModel = astFactory.createName(tempVarName, makeIteratorCall.getJSType());
Node tempDecl = IR.var(tempVarModel.cloneNode(), makeIteratorCall);
tempDecl.useSourceInfoIfMissingFromForTree(arrayPattern);
nodeToDetach.getParent().addChildBefore(tempDecl, nodeToDetach);
for (Node child = arrayPattern.getFirstChild(), next; child != null; child = next) {
next = child.getNext();
if (child.isEmpty()) {
// Just call the next() method to advance the iterator, but throw away the value.
Node nextCall =
IR.exprResult(
astFactory.createCall(astFactory.createGetProp(tempVarModel.cloneNode(), "next")));
nextCall.useSourceInfoIfMissingFromForTree(child);
nodeToDetach.getParent().addChildBefore(nextCall, nodeToDetach);
continue;
}
Node newLHS;
Node newRHS;
if (child.isDefaultValue()) {
// [x = defaultValue] = rhs;
// becomes
// var temp0 = $jscomp.makeIterator(rhs);
// var temp1 = temp.next().value
// x = (temp1 === undefined) ? defaultValue : temp1;
String nextVarName = getTempVariableName();
// `temp.next().value`
Node nextCallDotValue =
astFactory.createGetProp(
astFactory.createCall(astFactory.createGetProp(tempVarModel.cloneNode(), "next")),
"value");
JSType nextVarType = nextCallDotValue.getJSType();
// `var temp1 = temp.next().value`
Node var = IR.var(astFactory.createName(nextVarName, nextVarType), nextCallDotValue);
var.useSourceInfoIfMissingFromForTree(child);
nodeToDetach.getParent().addChildBefore(var, nodeToDetach);
// `x`
newLHS = child.getFirstChild().detach();
// `(temp1 === undefined) ? defaultValue : temp1;
newRHS =
defaultValueHook(
astFactory.createName(nextVarName, nextVarType), child.getLastChild().detach());
} else if (child.isRest()) {
// [...x] = rhs;
// becomes
// var temp = $jscomp.makeIterator(rhs);
// x = $jscomp.arrayFromIterator(temp);
newLHS = child.getFirstChild().detach();
newRHS =
astFactory.createJscompArrayFromIteratorCall(tempVarModel.cloneNode(), t.getScope());
} else {
// LHS is just a name (or a nested pattern).
// var [x] = rhs;
// becomes
// var temp = $jscomp.makeIterator(rhs);
// var x = temp.next().value;
newLHS = child.detach();
newRHS =
astFactory.createGetProp(
astFactory.createCall(astFactory.createGetProp(tempVarModel.cloneNode(), "next")),
"value");
}
Node newNode;
if (parent.isAssign()) {
Node assignment = astFactory.createAssign(newLHS, newRHS);
newNode = IR.exprResult(assignment);
} else {
newNode = IR.declaration(newLHS, newRHS, parent.getToken());
}
newNode.useSourceInfoIfMissingFromForTree(arrayPattern);
nodeToDetach.getParent().addChildBefore(newNode, nodeToDetach);
// Explicitly visit the LHS of the new node since it may be a nested
// destructuring pattern.
visit(t, newLHS, newLHS.getParent());
}
nodeToDetach.detach();
t.reportCodeChange();
}
/**
* Convert the assignment '[x, y] = rhs' that is used as an expression and not an expr result to:
* (() => let temp0 = rhs; var temp1 = $jscomp.makeIterator(temp0); var x = temp0.next().value;
* var y = temp0.next().value; return temp0; }) And the assignment '{x: a, y: b} = rhs' used as an
* expression and not an expr result to: (() => let temp0 = rhs; var temp1 = temp0; var a =
* temp0.x; var b = temp0.y; return temp0; })
*/
private void wrapAssignmentInCallToArrow(NodeTraversal t, Node assignment) {
String tempVarName = getTempVariableName();
Node tempVarModel = astFactory.createName(tempVarName, assignment.getJSType());
Node rhs = assignment.getLastChild().detach();
// let temp0 = rhs;
Node newAssignment = IR.let(tempVarModel.cloneNode(), rhs);
NodeUtil.addFeatureToScript(t.getCurrentScript(), Feature.LET_DECLARATIONS);
// [x, y] = temp0;
Node replacementExpr =
astFactory.createAssign(assignment.getFirstChild().detach(), tempVarModel.cloneNode());
Node exprResult = IR.exprResult(replacementExpr);
// return temp0;
Node returnNode = IR.returnNode(tempVarModel.cloneNode());
// Create a function to hold these assignments:
Node block = IR.block(newAssignment, exprResult, returnNode);
Node arrowFn = astFactory.createZeroArgFunction(/* name= */ "", block, assignment.getJSType());
arrowFn.setIsArrowFunction(true);
// Create a call to the function, and replace the pattern with the call.
Node call = astFactory.createCall(arrowFn);
NodeUtil.addFeatureToScript(t.getCurrentScript(), Feature.ARROW_FUNCTIONS);
call.useSourceInfoIfMissingFromForTree(assignment);
call.putBooleanProp(Node.FREE_CALL, true);
assignment.getParent().replaceChild(assignment, call);
NodeUtil.markNewScopesChanged(call, compiler);
replacePattern(
t,
replacementExpr.getFirstChild(),
replacementExpr.getLastChild(),
replacementExpr,
exprResult);
}
private void visitDestructuringPatternInEnhancedFor(Node pattern) {
checkArgument(pattern.isDestructuringPattern());
String tempVarName = getTempVariableName();
if (NodeUtil.isEnhancedFor(pattern.getParent())) {
// for ([a, b, c] of arr) {
Node forNode = pattern.getParent();
Node block = forNode.getLastChild();
Node decl = IR.var(astFactory.createName(tempVarName, pattern.getJSType()));
decl.useSourceInfoIfMissingFromForTree(pattern);
forNode.replaceChild(pattern, decl);
Node exprResult =
IR.exprResult(
astFactory.createAssign(
pattern, astFactory.createName(tempVarName, pattern.getJSType())));
exprResult.useSourceInfoIfMissingFromForTree(pattern);
block.addChildToFront(exprResult);
} else {
// for (const [a, b, c] of arr) {
Node destructuringLhs = pattern.getParent();
checkState(destructuringLhs.isDestructuringLhs());
Node declarationNode = destructuringLhs.getParent();
Node forNode = declarationNode.getParent();
checkState(NodeUtil.isEnhancedFor(forNode));
Node block = forNode.getLastChild();
declarationNode.replaceChild(
destructuringLhs,
astFactory.createName(tempVarName, pattern.getJSType()).useSourceInfoFrom(pattern));
Token declarationType = declarationNode.getToken();
Node decl =
IR.declaration(
pattern.detach(),
astFactory.createName(tempVarName, pattern.getJSType()),
declarationType);
decl.useSourceInfoIfMissingFromForTree(pattern);
// Move the body into an inner block to handle cases where declared variables in the for
// loop initializer are shadowed by variables in the for loop body. e.g.
// for (const [value] of []) { const value = 1; }
Node newBlock = IR.block(decl);
block.replaceWith(newBlock);
newBlock.addChildToBack(block);
}
}
private void visitDestructuringPatternInCatch(NodeTraversal t, Node pattern) {
String tempVarName = getTempVariableName();
Node catchBlock = pattern.getNext();
pattern.replaceWith(astFactory.createName(tempVarName, pattern.getJSType()));
catchBlock.addChildToFront(
IR.declaration(
pattern, astFactory.createName(tempVarName, pattern.getJSType()), Token.LET));
NodeUtil.addFeatureToScript(t.getCurrentScript(), Feature.LET_DECLARATIONS);
}
/** Helper for transpiling DEFAULT_VALUE trees. */
private Node defaultValueHook(Node getprop, Node defaultValue) {
Node undefined = astFactory.createName("undefined", JSTypeNative.VOID_TYPE);
undefined.makeNonIndexable();
Node getpropClone = getprop.cloneTree().setJSType(getprop.getJSType());
return astFactory.createHook(
astFactory.createSheq(getprop, undefined), defaultValue, getpropClone);
}
}