Class fields, part 1 (parsing and infrastructure)

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 179 matching lines @@
         stack_overflow_(false),
         allow_lazy_(false),
         allow_natives_(false),
         allow_tailcalls_(false),
         allow_harmony_restrictive_declarations_(false),
         allow_harmony_do_expressions_(false),
         allow_harmony_for_in_(false),
         allow_harmony_function_sent_(false),
         allow_harmony_async_await_(false),
         allow_harmony_restrictive_generators_(false),
-        allow_harmony_trailing_commas_(false) {}
+        allow_harmony_trailing_commas_(false),
+        allow_harmony_class_fields_(false) {}
 
 #define ALLOW_ACCESSORS(name)                           \
   bool allow_##name() const { return allow_##name##_; } \
   void set_allow_##name(bool allow) { allow_##name##_ = allow; }
 
   ALLOW_ACCESSORS(lazy);
   ALLOW_ACCESSORS(natives);
   ALLOW_ACCESSORS(tailcalls);
   ALLOW_ACCESSORS(harmony_restrictive_declarations);
   ALLOW_ACCESSORS(harmony_do_expressions);
   ALLOW_ACCESSORS(harmony_for_in);
   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);
 
 #undef ALLOW_ACCESSORS
 
   uintptr_t stack_limit() const { return stack_limit_; }
 
   void set_stack_limit(uintptr_t stack_limit) { stack_limit_ = stack_limit; }
 
   Zone* zone() const { return zone_; }
 
  protected:
@@ skipping 859 matching lines @@
   // specification).
   ExpressionT ParseExpressionCoverGrammar(bool accept_IN, bool* ok);
 
   ExpressionT ParseArrayLiteral(bool* ok);
 
   enum class PropertyKind {
     kAccessorProperty,
     kValueProperty,
     kShorthandProperty,
     kMethodProperty,
+    kClassField,
     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(
       ClassLiteralChecker* checker, bool has_extends, bool* is_computed_name,
       bool* has_seen_constructor, bool* ok);
+  FunctionLiteralT ParseClassFieldForInitializer(bool has_initializer,
+                                                 bool* ok);
   ObjectLiteralPropertyT ParseObjectPropertyDefinition(
       ObjectLiteralChecker* checker, bool* is_computed_name, bool* ok);
   ExpressionListT ParseArguments(Scanner::Location* first_spread_pos,
                                  bool maybe_arrow, bool* ok);
   ExpressionListT ParseArguments(Scanner::Location* first_spread_pos,
                                  bool* ok) {
     return ParseArguments(first_spread_pos, false, ok);
   }
 
   ExpressionT ParseAssignmentExpression(bool accept_IN, bool* ok);
@@ skipping 211 matching lines @@
   bool allow_lazy_;
   bool allow_natives_;
   bool allow_tailcalls_;
   bool allow_harmony_restrictive_declarations_;
   bool allow_harmony_do_expressions_;
   bool allow_harmony_for_in_;
   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_;
 
   friend class DiscardableZoneScope;
 };
 
 template <typename Impl>
 ParserBase<Impl>::FunctionState::FunctionState(
     FunctionState** function_state_stack, ScopeState** scope_stack,
     Scope* scope, FunctionKind kind)
     : ScopeState(scope_stack, scope),
       next_materialized_literal_index_(0),
@@ skipping 535 matching lines @@
       *kind = PropertyKind::kValueProperty;
       return true;
     case Token::COMMA:
     case Token::RBRACE:
     case Token::ASSIGN:
       *kind = PropertyKind::kShorthandProperty;
       return true;
     case Token::LPAREN:
       *kind = PropertyKind::kMethodProperty;
       return true;
+    case Token::MUL:
+    case Token::SEMICOLON:
+      *kind = PropertyKind::kClassField;
+      return true;
     default:
       break;
   }
   return false;
 }
 
 template <class Impl>
 typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParsePropertyName(
     IdentifierT* name, PropertyKind* kind, bool* is_generator, bool* is_get,
     bool* is_set, bool* is_async, bool* is_computed_name, bool* ok) {
@@ skipping 117 matching lines @@
   Token::Value name_token = peek();
 
   IdentifierT name = impl()->EmptyIdentifier();
   ExpressionT name_expression;
   if (name_token == Token::STATIC) {
     Consume(Token::STATIC);
     if (peek() == Token::LPAREN) {
       kind = PropertyKind::kMethodProperty;
       name = impl()->GetSymbol();  // TODO(bakkot) specialize on 'static'
       name_expression = factory()->NewStringLiteral(name, position());
+    } else if (peek() == Token::ASSIGN || peek() == Token::SEMICOLON ||
+               peek() == Token::RBRACE) {
+      name = impl()->GetSymbol();  // TODO(bakkot) specialize on 'static'
+      name_expression = factory()->NewStringLiteral(name, position());
     } else {
       is_static = true;
       name_expression = ParsePropertyName(
           &name, &kind, &is_generator, &is_get, &is_set, &is_async,
           is_computed_name, CHECK_OK_CUSTOM(EmptyClassLiteralProperty));
     }
   } else {
     name_expression = ParsePropertyName(
         &name, &kind, &is_generator, &is_get, &is_set, &is_async,
         is_computed_name, CHECK_OK_CUSTOM(EmptyClassLiteralProperty));
   }
 
   switch (kind) {
+    case PropertyKind::kClassField:
+    case PropertyKind::kNotSet:  // This case is a name followed by a name or
+                                 // other property. Here we have to assume
+                                 // that's an uninitialized field followed by a
+                                 // linebreak followed by a property, with ASI
+                                 // adding the semicolon. If not, there will be
+                                 // a syntax error after parsing the first name
+                                 // as an uninitialized field.
     case PropertyKind::kShorthandProperty:
     case PropertyKind::kValueProperty:
-      ReportUnexpectedToken(Next());
-      *ok = false;
-      return impl()->EmptyClassLiteralProperty();
+      if (allow_harmony_class_fields()) {
+        bool has_initializer = Check(Token::ASSIGN);
+        ExpressionT function_literal = ParseClassFieldForInitializer(
+            has_initializer, CHECK_OK_CUSTOM(EmptyClassLiteralProperty));
+        ExpectSemicolon(CHECK_OK_CUSTOM(EmptyClassLiteralProperty));
+        return factory()->NewClassLiteralProperty(
+            name_expression, function_literal, ClassLiteralProperty::FIELD,
+            is_static, *is_computed_name);
+      } else {
+        ReportUnexpectedToken(Next());
+        *ok = false;
+        return impl()->EmptyClassLiteralProperty();
+      }
 
     case PropertyKind::kMethodProperty: {
       DCHECK(!is_get && !is_set);
 
       // MethodDefinition
       //    PropertyName '(' StrictFormalParameters ')' '{' FunctionBody '}'
       //    '*' PropertyName '(' StrictFormalParameters ')' '{' FunctionBody '}'
 
       if (!*is_computed_name) {
         checker->CheckClassMethodName(
@@ skipping 46 matching lines @@
 
       if (!*is_computed_name) {
         impl()->AddAccessorPrefixToFunctionName(is_get, value, name);
       }
 
       return factory()->NewClassLiteralProperty(
           name_expression, value,
           is_get ? ClassLiteralProperty::GETTER : ClassLiteralProperty::SETTER,
           is_static, *is_computed_name);
     }
-
-    case PropertyKind::kNotSet:
-      ReportUnexpectedToken(Next());
-      *ok = false;
-      return impl()->EmptyClassLiteralProperty();
   }
   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
+  // (or undefined if absent).
+  FunctionKind kind = FunctionKind::kConciseMethod;
+  DeclarationScope* initializer_scope = NewFunctionScope(kind);
+  initializer_scope->set_start_position(scanner()->location().end_pos);
+  FunctionState initializer_state(&function_state_, &scope_state_,
+                                  initializer_scope, kind);
+  DCHECK(scope() == initializer_scope);
+  scope()->SetLanguageMode(STRICT);
+  ExpressionClassifier expression_classifier(this);
+  ExpressionT value;
+  if (has_initializer) {
+    value = this->ParseAssignmentExpression(
+        true, CHECK_OK_CUSTOM(EmptyFunctionLiteral));
+    impl()->RewriteNonPattern(CHECK_OK_CUSTOM(EmptyFunctionLiteral));
+  } else {
+    value = factory()->NewUndefinedLiteral(kNoSourcePosition);
+  }
+  initializer_scope->set_end_position(scanner()->location().end_pos);
+  typename Types::StatementList body = impl()->NewStatementList(1);
+  body->Add(factory()->NewReturnStatement(value, kNoSourcePosition), zone());
+  FunctionLiteralT function_literal = factory()->NewFunctionLiteral(
+      impl()->EmptyIdentifierString(), initializer_scope, body,
+      initializer_state.materialized_literal_count(),
+      initializer_state.expected_property_count(), 0,
+      FunctionLiteral::kNoDuplicateParameters,
+      FunctionLiteral::kAnonymousExpression,
+      FunctionLiteral::kShouldLazyCompile, kind,
+      initializer_scope->start_position());
+  function_literal->set_is_class_field_initializer(true);
+  return function_literal;
+}
+
+template <typename Impl>
 typename ParserBase<Impl>::ObjectLiteralPropertyT
 ParserBase<Impl>::ParseObjectPropertyDefinition(ObjectLiteralChecker* checker,
                                                 bool* is_computed_name,
                                                 bool* ok) {
   bool is_get = false;
   bool is_set = false;
   bool is_generator = false;
   bool is_async = false;
   PropertyKind kind = PropertyKind::kNotSet;
 
@@ skipping 149 matching lines @@
       if (!*is_computed_name) {
         impl()->AddAccessorPrefixToFunctionName(is_get, value, name);
       }
 
       return factory()->NewObjectLiteralProperty(
           name_expression, value, is_get ? ObjectLiteralProperty::GETTER
                                          : ObjectLiteralProperty::SETTER,
           *is_computed_name);
     }
 
+    case PropertyKind::kClassField:
     case PropertyKind::kNotSet:
       ReportUnexpectedToken(Next());
       *ok = false;
       return impl()->EmptyObjectLiteralProperty();
   }
   UNREACHABLE();
   return impl()->EmptyObjectLiteralProperty();
 }
 
 template <typename Impl>
@@ skipping 1938 matching lines @@
     has_seen_constructor_ = true;
     return;
   }
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_BASE_H