[ESnext] Implement Object spread

src/parsing/parser-base.h

 // 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.
 
 #ifndef V8_PARSING_PARSER_BASE_H
 #define V8_PARSING_PARSER_BASE_H
 
 #include "src/ast/ast.h"
 #include "src/ast/scopes.h"
 #include "src/bailout-reason.h"
@@ skipping 199 matching lines @@
         stack_overflow_(false),
         default_eager_compile_hint_(FunctionLiteral::kShouldLazyCompile),
         function_literal_id_(0),
         allow_natives_(false),
         allow_tailcalls_(false),
         allow_harmony_do_expressions_(false),
         allow_harmony_function_sent_(false),
         allow_harmony_async_await_(false),
         allow_harmony_restrictive_generators_(false),
         allow_harmony_trailing_commas_(false),
-        allow_harmony_class_fields_(false) {}
+        allow_harmony_class_fields_(false),
+        allow_harmony_object_spread_(false) {}
 
 #define ALLOW_ACCESSORS(name)                           \
   bool allow_##name() const { return allow_##name##_; } \
   void set_allow_##name(bool allow) { allow_##name##_ = allow; }
 
   ALLOW_ACCESSORS(natives);
   ALLOW_ACCESSORS(tailcalls);
   ALLOW_ACCESSORS(harmony_do_expressions);
   ALLOW_ACCESSORS(harmony_function_sent);
   ALLOW_ACCESSORS(harmony_async_await);
   ALLOW_ACCESSORS(harmony_restrictive_generators);
   ALLOW_ACCESSORS(harmony_trailing_commas);
   ALLOW_ACCESSORS(harmony_class_fields);
+  ALLOW_ACCESSORS(harmony_object_spread);
 
 #undef ALLOW_ACCESSORS
 
   uintptr_t stack_limit() const { return stack_limit_; }
 
   void set_stack_limit(uintptr_t stack_limit) { stack_limit_ = stack_limit; }
 
   void set_default_eager_compile_hint(
       FunctionLiteral::EagerCompileHint eager_compile_hint) {
     default_eager_compile_hint_ = eager_compile_hint;
@@ skipping 898 matching lines @@
   ExpressionT ParseExpressionCoverGrammar(bool accept_IN, bool* ok);
 
   ExpressionT ParseArrayLiteral(bool* ok);
 
   enum class PropertyKind {
     kAccessorProperty,
     kValueProperty,
     kShorthandProperty,
     kMethodProperty,
     kClassField,
+    kSpreadProperty,
     kNotSet
   };
 
   bool SetPropertyKindFromToken(Token::Value token, PropertyKind* kind);
   ExpressionT ParsePropertyName(IdentifierT* name, PropertyKind* kind,
                                 bool* is_generator, bool* is_get, bool* is_set,
                                 bool* is_async, bool* is_computed_name,
                                 bool* ok);
   ExpressionT ParseObjectLiteral(bool* ok);
   ClassLiteralPropertyT ParseClassPropertyDefinition(
@@ skipping 286 matching lines @@
   int function_literal_id_;
 
   bool allow_natives_;
   bool allow_tailcalls_;
   bool allow_harmony_do_expressions_;
   bool allow_harmony_function_sent_;
   bool allow_harmony_async_await_;
   bool allow_harmony_restrictive_generators_;
   bool allow_harmony_trailing_commas_;
   bool allow_harmony_class_fields_;
+  bool allow_harmony_object_spread_;
 
   friend class DiscardableZoneScope;
 };
 
 template <typename Impl>
 ParserBase<Impl>::FunctionState::FunctionState(
     FunctionState** function_state_stack, ScopeState** scope_stack,
     DeclarationScope* scope)
     : ScopeState(scope_stack, scope),
       next_materialized_literal_index_(0),
@@ skipping 633 matching lines @@
       *is_computed_name = true;
       Consume(Token::LBRACK);
       ExpressionClassifier computed_name_classifier(this);
       expression = ParseAssignmentExpression(true, CHECK_OK);
       impl()->RewriteNonPattern(CHECK_OK);
       impl()->AccumulateFormalParameterContainmentErrors();
       Expect(Token::RBRACK, CHECK_OK);
       break;
     }
 
+    case Token::ELLIPSIS: {
+      if (allow_harmony_object_spread()) {
+        // TODO(gsathya): Implement destructuring/rest
+        BindingPatternUnexpectedToken();

[adamk, 2016/12/29 00:48:45]

I think you'll need to disallow this in assignment patterns too. A negative test
for this would demonstrate that.

var {...x} = {};

will fail, but

({...x} = {})

will succeed

[gsathya, 2016/12/29 06:40:56]

Done.

[adamk, 2016/12/29 18:32:45]

You can get both at once with

classifier()->RecordPatternError(...)

[gsathya, 2017/01/05 22:18:35]

Done.

+
+        *name = impl()->EmptyIdentifier();
+        Consume(Token::ELLIPSIS);
+        ExpressionClassifier spread_classifier(this);
+        expression = ParseAssignmentExpression(false, CHECK_OK);

[adamk, 2016/12/29 00:48:45]

Don't you want to accept "in"? Please add a test, like

{...1 in {}}

[gsathya, 2016/12/29 06:40:56]

Done.

+        impl()->RewriteNonPattern(CHECK_OK);
+        impl()->AccumulateFormalParameterContainmentErrors();
+        *kind = PropertyKind::kSpreadProperty;
+        return expression;
+      }
+    }
+
     default:
       *name = ParseIdentifierName(CHECK_OK);
       break;
   }
 
   if (*kind == PropertyKind::kNotSet) {
     SetPropertyKindFromToken(peek(), kind);
   }
 
   if (*is_computed_name) {
@@ skipping 140 matching lines @@
       if (!*is_computed_name) {
         impl()->AddAccessorPrefixToFunctionName(is_get, value, name);
       }
 
       *property_kind =
           is_get ? ClassLiteralProperty::GETTER : ClassLiteralProperty::SETTER;
       return factory()->NewClassLiteralProperty(name_expression, value,
                                                 *property_kind, *is_static,
                                                 *is_computed_name);
     }
+    case PropertyKind::kSpreadProperty:
+      UNREACHABLE();
   }
   UNREACHABLE();
   return impl()->EmptyClassLiteralProperty();
 }
 
 template <typename Impl>
 typename ParserBase<Impl>::FunctionLiteralT
 ParserBase<Impl>::ParseClassFieldForInitializer(bool has_initializer,
                                                 bool* ok) {
   // Makes a concise method which evaluates and returns the initialized value
@@ skipping 41 matching lines @@
   IdentifierT name = impl()->EmptyIdentifier();
   Token::Value name_token = peek();
   int next_beg_pos = scanner()->peek_location().beg_pos;
   int next_end_pos = scanner()->peek_location().end_pos;
 
   ExpressionT name_expression = ParsePropertyName(
       &name, &kind, &is_generator, &is_get, &is_set, &is_async,
       is_computed_name, CHECK_OK_CUSTOM(EmptyObjectLiteralProperty));
 
   switch (kind) {
+    case PropertyKind::kSpreadProperty: {
+      if (allow_harmony_object_spread()) {

[adamk, 2016/12/29 00:48:45]

This can be a DCHECK, since ParsePropertyName shouldn't set kSpreadProperty
unless the flag is on anyway.

[gsathya, 2016/12/29 06:40:56]

Done.

+        DCHECK(!is_get && !is_set && !is_generator && !is_async);

[adamk, 2016/12/29 00:48:45]

you should add !*is_computed_name to this list.

[gsathya, 2016/12/29 06:40:56]

Done.

+        DCHECK(name_token == Token::ELLIPSIS);
+
+        *is_computed_name = true;
+        *ok = true;

[adamk, 2016/12/29 00:48:45]

No need to set *ok to true, that's how it starts. Only need to set to false on
failure.

[gsathya, 2016/12/29 06:40:56]

Done.

+
+        return factory()->NewObjectLiteralProperty(
+            impl()->GetLiteralTheHole(kNoSourcePosition), name_expression,
+            ObjectLiteralProperty::SPREAD, true);
+      }
+    }
+
     case PropertyKind::kValueProperty: {
       DCHECK(!is_get && !is_set && !is_generator && !is_async);
 
       if (!*is_computed_name) {
         checker->CheckDuplicateProto(name_token);
       }
       Consume(Token::COLON);
       int beg_pos = peek_position();
       ExpressionT value = ParseAssignmentExpression(
           true, CHECK_OK_CUSTOM(EmptyObjectLiteralProperty));
@@ skipping 3156 matching lines @@
     has_seen_constructor_ = true;
     return;
   }
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_BASE_H