[ESnext] Implement Object spread

src/parsing/parser-base.h

Index: src/parsing/parser-base.h
diff --git a/src/parsing/parser-base.h b/src/parsing/parser-base.h
index 9ce9c32309328c7cc890f4877ed169897099685b..b4808dddc9dad0dbfcb108e51e2ca98a949270de 100644
--- a/src/parsing/parser-base.h
+++ b/src/parsing/parser-base.h
@@ -217,7 +217,8 @@ class ParserBase {
         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##_; } \
@@ -231,6 +232,7 @@ class ParserBase {
   ALLOW_ACCESSORS(harmony_restrictive_generators);
   ALLOW_ACCESSORS(harmony_trailing_commas);
   ALLOW_ACCESSORS(harmony_class_fields);
+  ALLOW_ACCESSORS(harmony_object_spread);
 
 #undef ALLOW_ACCESSORS
 
@@ -1149,6 +1151,7 @@ class ParserBase {
     kShorthandProperty,
     kMethodProperty,
     kClassField,
+    kSpreadProperty,
     kNotSet
   };
 
@@ -1455,6 +1458,7 @@ class ParserBase {
   bool allow_harmony_restrictive_generators_;
   bool allow_harmony_trailing_commas_;
   bool allow_harmony_class_fields_;
+  bool allow_harmony_object_spread_;
 
   friend class DiscardableZoneScope;
 };
@@ -2108,6 +2112,22 @@ typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParsePropertyName(
       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;
@@ -2268,6 +2288,8 @@ ParserBase<Impl>::ParseClassPropertyDefinition(
                                                 *property_kind, *is_static,
                                                 *is_computed_name);
     }
+    case PropertyKind::kSpreadProperty:
+      UNREACHABLE();
   }
   UNREACHABLE();
   return impl()->EmptyClassLiteralProperty();
@@ -2329,6 +2351,20 @@ ParserBase<Impl>::ParseObjectPropertyDefinition(ObjectLiteralChecker* checker,
       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);