[parser] Change how we detect let as lexical declaration

Change-Id: I907ace62da903dd57cb86b608c0f96ac49623976
Reviewed-on: https://chromium-review.googlesource.com/c/1426130
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58991}

src/parsing/expression-scope.h

@@ -282,7 +282,12 @@ class VariableDeclarationParsingScope : public ExpressionScope<Types> {
       this->parser()->ReportMessage(MessageTemplate::kTooManyVariables);
     }
     if (names_) names_->Add(proxy->raw_name(), this->parser()->zone());
-    if (!this->IsLexicalDeclaration()) {
+    if (this->IsLexicalDeclaration()) {
+      if (this->parser()->IsLet(proxy->raw_name())) {
+        this->parser()->ReportMessageAt(proxy->location(),
+                                        MessageTemplate::kLetInLexicalBinding);
+      }
+    } else {
       if (this->parser()->loop_nesting_depth() > 0) {
         // Due to hoisting, the value of a 'var'-declared variable may actually
         // change even if the code contains only the "initial" assignment,

src/parsing/parser-base.h

@@ -1158,6 +1158,10 @@ class ParserBase {
       ZonePtrList<const AstRawString>* labels,
       ZonePtrList<const AstRawString>* own_labels);
 
+  V8_INLINE bool IsLet(const AstRawString* identifier) const {
+    return identifier == ast_value_factory()->let_string();
+  }
+
   void DesugarBindingInForEachStatement(ForInfo* for_info, BlockT* body_block,
                                         ExpressionT* each_variable) {
     // Annex B.3.5 prohibits the form
@@ -3488,16 +3492,6 @@ void ParserBase<Impl>::ParseVariableDeclarations(
     int decl_pos = peek_position();
     ExpressionT pattern = ParseBindingPattern();
 
-    if (IsLexicalVariableMode(parsing_result->descriptor.mode)) {
-      if (impl()->IsIdentifier(pattern)) {
-        if (impl()->IsLet(impl()->AsIdentifier(pattern))) {
-          impl()->ReportMessageAt(
-              Scanner::Location(bindings_start, end_position()),
-              MessageTemplate::kLetInLexicalBinding);
-        }
-      }
-    }
-
     Scanner::Location variable_loc = scanner()->location();
 
     ExpressionT value = impl()->NullExpression();
@@ -4376,11 +4370,6 @@ ParserBase<Impl>::ParsePossibleDestructuringSubPattern(
       }
       IdentifierT identifier = impl()->AsIdentifier(result);
       ClassifyParameter(identifier, begin, end_position());
-      if (impl()->IsLet(identifier)) {
-        expression_scope()->RecordLexicalDeclarationError(
-            Scanner::Location(begin, end_position()),
-            MessageTemplate::kLetInLexicalBinding);
-      }
     } else {
       DCHECK(result->IsProperty());
       expression_scope()->RecordDeclarationError(

src/parsing/parser.h

@@ -568,10 +568,6 @@ class V8_EXPORT_PRIVATE Parser : public NON_EXPORTED_BASE(ParserBase<Parser>) {
     return identifier == ast_value_factory()->arguments_string();
   }
 
-  V8_INLINE bool IsLet(const AstRawString* identifier) const {
-    return identifier == ast_value_factory()->let_string();
-  }
-
   V8_INLINE bool IsEvalOrArguments(const AstRawString* identifier) const {
     return IsEval(identifier) || IsArguments(identifier);
   }

src/parsing/preparser.cc

@@ -28,8 +28,6 @@ PreParserIdentifier GetSymbolHelper(Scanner* scanner,
   // - 'contextual' keywords (and may contain escaped; treated in 2nd switch.)
   // - 'contextual' keywords, but may not be escaped (3rd switch).
   switch (scanner->current_token()) {
-    case Token::LET:
-      return PreParserIdentifier::Let();
     case Token::AWAIT:
       return PreParserIdentifier::Await();
     case Token::ASYNC:
@@ -46,9 +44,6 @@ PreParserIdentifier GetSymbolHelper(Scanner* scanner,
     return PreParserIdentifier::Name();
   }
   if (scanner->literal_contains_escapes()) {
-    if (string == avf->let_string()) {
-      return PreParserIdentifier::Let();
-    }
     return PreParserIdentifier::Default();
   }
   if (string == avf->eval_string()) {

src/parsing/preparser.h

@@ -45,9 +45,6 @@ class PreParserIdentifier {
   static PreParserIdentifier Await() {
     return PreParserIdentifier(kAwaitIdentifier);
   }
-  static PreParserIdentifier Let() {
-    return PreParserIdentifier(kLetIdentifier);
-  }
   static PreParserIdentifier Async() {
     return PreParserIdentifier(kAsyncIdentifier);
   }
@@ -67,7 +64,6 @@ class PreParserIdentifier {
   }
   bool IsConstructor() const { return type_ == kConstructorIdentifier; }
   bool IsAwait() const { return type_ == kAwaitIdentifier; }
-  bool IsLet() const { return type_ == kLetIdentifier; }
   bool IsName() const { return type_ == kNameIdentifier; }
   bool IsPrivateName() const { return type_ == kPrivateNameIdentifier; }
 
@@ -79,7 +75,6 @@ class PreParserIdentifier {
     kArgumentsIdentifier,
     kConstructorIdentifier,
     kAwaitIdentifier,
-    kLetIdentifier,
     kAsyncIdentifier,
     kNameIdentifier,
     kPrivateNameIdentifier
@@ -1288,10 +1283,6 @@ class PreParser : public ParserBase<PreParser> {
     return identifier.IsAwait();
   }
 
-  V8_INLINE bool IsLet(const PreParserIdentifier& identifier) const {
-    return identifier.IsLet();
-  }
-
   // Returns true if the expression is of type "this.foo".
   V8_INLINE static bool IsThisProperty(const PreParserExpression& expression) {
     return expression.IsThisProperty();