[destructuring] Implement initializers in patterns.

src/pattern-rewriter.cc

Index: src/pattern-rewriter.cc
diff --git a/src/pattern-rewriter.cc b/src/pattern-rewriter.cc
index 09f9489e676211128c965a44f632843ea846ce0d..136dc5c1d919b945b61f102bb80528eedcb6d288 100644
--- a/src/pattern-rewriter.cc
+++ b/src/pattern-rewriter.cc
@@ -207,16 +207,22 @@ void Parser::PatternRewriter::VisitVariableProxy(VariableProxy* pattern) {
 }
 
 
-void Parser::PatternRewriter::VisitObjectLiteral(ObjectLiteral* pattern) {
-  auto temp = descriptor_->declaration_scope->NewTemporary(
+Variable* Parser::PatternRewriter::CreateTemp(Expression* value) {

[arv (Not doing code reviews), 2015/05/18 14:36:20]

CreateTempVar maybe?

[Dmitry Lomov (no reviews), 2015/05/18 17:31:22]

Done.

+  auto temp = TemporaryDeclarationScope()->NewTemporary(
       ast_value_factory()->empty_string());
   auto assignment =
       factory()->NewAssignment(Token::ASSIGN, factory()->NewVariableProxy(temp),
-                               current_value_, RelocInfo::kNoPosition);
+                               value, RelocInfo::kNoPosition);
 
   block_->AddStatement(
       factory()->NewExpressionStatement(assignment, RelocInfo::kNoPosition),
       zone());
+  return temp;
+}
+
+
+void Parser::PatternRewriter::VisitObjectLiteral(ObjectLiteral* pattern) {
+  auto temp = CreateTemp(current_value_);
   block_->AddStatement(descriptor_->parser->BuildAssertIsCoercible(temp),
                        zone());
 
@@ -236,7 +242,16 @@ void Parser::PatternRewriter::VisitArrayLiteral(ArrayLiteral* node) {
 
 
 void Parser::PatternRewriter::VisitAssignment(Assignment* node) {
-  // TODO(dslomov): implement.
+  DCHECK(node->op() == Token::ASSIGN);

[arv (Not doing code reviews), 2015/05/18 14:36:20]

Maybe add a comment explaining the desugaring

  let {<pattern> = init} = <current_value>

becomes

  temp = <current_value>
  <pattern> = temp === undefined ? init : temp

[Dmitry Lomov (no reviews), 2015/05/18 17:31:22]

Done.

+  auto temp = CreateTemp(current_value_);
+  Expression* is_undefined = factory()->NewCompareOperation(
+      Token::EQ_STRICT, factory()->NewVariableProxy(temp),
+      factory()->NewUndefinedLiteral(RelocInfo::kNoPosition),
+      RelocInfo::kNoPosition);
+  Expression* value = factory()->NewConditional(
+      is_undefined, node->value(), factory()->NewVariableProxy(temp),
+      RelocInfo::kNoPosition);
+  RecurseIntoSubpattern(node->target(), value);
 }