[es6] implement destructuring assignment

src/parsing/parser.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/parsing/parser.h"
 
 #include "src/api.h"
 #include "src/ast/ast.h"
+#include "src/ast/ast-expression-visitor.h"
 #include "src/ast/ast-literal-reindexer.h"
 #include "src/ast/scopeinfo.h"
 #include "src/bailout-reason.h"
 #include "src/base/platform/platform.h"
 #include "src/bootstrapper.h"
 #include "src/char-predicates-inl.h"
 #include "src/codegen.h"
 #include "src/compiler.h"
 #include "src/messages.h"
 #include "src/parsing/parameter-initializer-rewriter.h"
@@ skipping 897 matching lines @@
   // ParseInfo during background parsing.
   DCHECK(!info->script().is_null() || info->source_stream() != NULL);
   set_allow_lazy(info->allow_lazy_parsing());
   set_allow_natives(FLAG_allow_natives_syntax || info->is_native());
   set_allow_harmony_sloppy(FLAG_harmony_sloppy);
   set_allow_harmony_sloppy_function(FLAG_harmony_sloppy_function);
   set_allow_harmony_sloppy_let(FLAG_harmony_sloppy_let);
   set_allow_harmony_rest_parameters(FLAG_harmony_rest_parameters);
   set_allow_harmony_default_parameters(FLAG_harmony_default_parameters);
   set_allow_harmony_destructuring_bind(FLAG_harmony_destructuring_bind);
+  set_allow_harmony_destructuring_assignment(
+      FLAG_harmony_destructuring_assignment);
   set_allow_strong_mode(FLAG_strong_mode);
   set_allow_legacy_const(FLAG_legacy_const);
   set_allow_harmony_do_expressions(FLAG_harmony_do_expressions);
   for (int feature = 0; feature < v8::Isolate::kUseCounterFeatureCount;
        ++feature) {
     use_counts_[feature] = 0;
   }
   if (info->ast_value_factory() == NULL) {
     // info takes ownership of AstValueFactory.
     info->set_ast_value_factory(new AstValueFactory(zone(), info->hash_seed()));
@@ skipping 150 matching lines @@
       if (body->length() != 1 ||
           !body->at(0)->IsExpressionStatement() ||
           !body->at(0)->AsExpressionStatement()->
               expression()->IsFunctionLiteral()) {
         ReportMessage(MessageTemplate::kSingleFunctionLiteral);
         ok = false;
       }
     }
 
     if (ok) {
+      ParserTraits::RewriteDestructuringAssignments();
       result = factory()->NewFunctionLiteral(
           ast_value_factory()->empty_string(), ast_value_factory(), scope_,
           body, function_state.materialized_literal_count(),
           function_state.expected_property_count(), 0,
           FunctionLiteral::kNoDuplicateParameters,
           FunctionLiteral::ANONYMOUS_EXPRESSION, FunctionLiteral::kGlobalOrEval,
           FunctionLiteral::kShouldLazyCompile, FunctionKind::kNormalFunction,
           0);
     }
   }
@@ skipping 3291 matching lines @@
       CheckStrictOctalLiteral(scope->start_position(), scope->end_position(),
                               CHECK_OK);
     }
     if (is_sloppy(language_mode) && allow_harmony_sloppy_function()) {
       InsertSloppyBlockFunctionVarBindings(scope, CHECK_OK);
     }
     if (is_strict(language_mode) || allow_harmony_sloppy() ||
         allow_harmony_destructuring_bind()) {
       CheckConflictingVarDeclarations(scope, CHECK_OK);
     }
+
+    if (body) {
+      // If body can be inspected, rewrite queued destructuring assignments
+      ParserTraits::RewriteDestructuringAssignments();
+    }
   }
 
   bool has_duplicate_parameters =
       !formals_classifier.is_valid_formal_parameter_list_without_duplicates();
   FunctionLiteral::ParameterFlag duplicate_parameters =
       has_duplicate_parameters ? FunctionLiteral::kHasDuplicateParameters
                                : FunctionLiteral::kNoDuplicateParameters;
 
   FunctionLiteral* function_literal = factory()->NewFunctionLiteral(
       function_name, ast_value_factory(), scope, body,
@@ skipping 108 matching lines @@
       RelocInfo::kNoPosition);
   IfStatement* if_statement = factory()->NewIfStatement(
       condition, factory()->NewExpressionStatement(throw_type_error,
                                                    RelocInfo::kNoPosition),
       factory()->NewEmptyStatement(RelocInfo::kNoPosition),
       RelocInfo::kNoPosition);
   return if_statement;
 }
 
 
+class InitializerRewriter : public AstExpressionVisitor {
+ public:
+  InitializerRewriter(uintptr_t stack_limit, Expression* root, Parser* parser,
+                      Scope* scope)
+      : AstExpressionVisitor(stack_limit, root),
+        parser_(parser),
+        scope_(scope) {}
+
+ private:
+  void VisitExpression(Expression* expr) {
+    RewritableAssignmentExpression* to_rewrite =
+        expr->AsRewritableAssignmentExpression();
+    if (to_rewrite == nullptr || to_rewrite->is_rewritten()) return;
+
+    bool ok = true;
+    Parser::PatternRewriter::RewriteDestructuringAssignment(parser_, to_rewrite,
+                                                            scope_, &ok);
+    DCHECK(ok);
+  }
+
+ private:
+  Parser* parser_;
+  Scope* scope_;
+};
+
+
+void Parser::RewriteParameterInitializer(Expression* expr, Scope* scope) {
+  InitializerRewriter rewriter(stack_limit_, expr, this, scope);
+  rewriter.Run();
+}
+
+
 Block* Parser::BuildParameterInitializationBlock(
     const ParserFormalParameters& parameters, bool* ok) {
   DCHECK(!parameters.is_simple);
   DCHECK(scope_->is_function_scope());
   Block* init_block =
       factory()->NewBlock(NULL, 1, true, RelocInfo::kNoPosition);
   for (int i = 0; i < parameters.params.length(); ++i) {
     auto parameter = parameters.params[i];
     DeclarationDescriptor descriptor;
     descriptor.declaration_kind = DeclarationDescriptor::PARAMETER;
@@ skipping 10 matching lines @@
     // it's just copying from a temp var to the real param var?
     descriptor.initialization_pos = parameter.pattern->position();
     // The initializer position which will end up in,
     // Variable::initializer_position(), used for hole check elimination.
     int initializer_position = parameter.pattern->position();
     Expression* initial_value =
         factory()->NewVariableProxy(parameters.scope->parameter(i));
     if (parameter.initializer != nullptr) {
       // IS_UNDEFINED($param) ? initializer : $param
       DCHECK(!parameter.is_rest);
+
+      // Ensure initializer is rewritten
+      RewriteParameterInitializer(parameter.initializer, scope_);
+
       auto condition = factory()->NewCompareOperation(
           Token::EQ_STRICT,
           factory()->NewVariableProxy(parameters.scope->parameter(i)),
           factory()->NewUndefinedLiteral(RelocInfo::kNoPosition),
           RelocInfo::kNoPosition);
       initial_value = factory()->NewConditional(
           condition, parameter.initializer, initial_value,
           RelocInfo::kNoPosition);
       descriptor.initialization_pos = parameter.initializer->position();
       initializer_position = parameter.initializer_end_position;
@@ skipping 1883 matching lines @@
   ++use_counts_[feature];
   scope->SetLanguageMode(mode);
 }
 
 
 void Parser::RaiseLanguageMode(LanguageMode mode) {
   SetLanguageMode(scope_,
                   static_cast<LanguageMode>(scope_->language_mode() | mode));
 }
 
+
+void ParserTraits::RewriteDestructuringAssignments() {
+  parser_->RewriteDestructuringAssignments();
+}
+
+
+void Parser::RewriteDestructuringAssignments() {
+  FunctionState* func = function_state_;
+  if (!allow_harmony_destructuring_assignment()) return;
+  const List<DestructuringAssignment>& assignments =
+      func->destructuring_assignments_to_rewrite();
+  for (int i = assignments.length() - 1; i >= 0; --i) {
+    // Rewrite list in reverse, so that nested assignment patterns are rewritten
+    // correctly.
+    DestructuringAssignment pair = assignments.at(i);
+    RewritableAssignmentExpression* to_rewrite =
+        pair.assignment->AsRewritableAssignmentExpression();
+    Scope* scope = pair.scope;
+    DCHECK_NOT_NULL(to_rewrite);
+    if (!to_rewrite->is_rewritten()) {
+      bool ok = true;
+      PatternRewriter::RewriteDestructuringAssignment(this, to_rewrite, scope,
+                                                      &ok);
+      DCHECK(ok);
+    }
+  }
+}
+
+
+void ParserTraits::QueueDestructuringAssignmentForRewriting(Expression* expr) {
+  DCHECK(expr->IsRewritableAssignmentExpression());
+  parser_->function_state_->AddDestructuringAssignment(
+      Parser::DestructuringAssignment(expr, parser_->scope_));
+}
+
+
 }  // namespace internal
 }  // namespace v8