[parser] Make it explicit when marking destructuring patterns as assigned

Divide MarkExpressionAsAssigned into MarkExpressionAsAssigned and
MarkPatternAsAssigned so it's clear when we need to mark just a single variable
or an entire destructuring assignment pattern.

Change-Id: Ia188b3d9b15944a1859676f483df229225ce8404
Reviewed-on: https://chromium-review.googlesource.com/c/1270945
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56505}

src/parsing/parser-base.h

@@ -2950,14 +2950,14 @@ ParserBase<Impl>::ParseAssignmentExpression(bool accept_IN, bool* ok) {
 
   if (is_destructuring_assignment) {
     ValidateAssignmentPattern(CHECK_OK);
+    impl()->MarkPatternAsAssigned(expression);
   } else {
     expression = CheckAndRewriteReferenceExpression(
         expression, lhs_beg_pos, end_position(),
         MessageTemplate::kInvalidLhsInAssignment, CHECK_OK);
+    impl()->MarkExpressionAsAssigned(expression);
   }
 
-  impl()->MarkExpressionAsAssigned(expression);
-
   Token::Value op = Next();  // Get assignment operator.
   if (op != Token::ASSIGN) {
     classifier()->RecordPatternError(scanner()->location(),

src/parsing/parser.h

@@ -710,6 +710,8 @@ class V8_EXPORT_PRIVATE Parser : public NON_EXPORTED_BASE(ParserBase<Parser>) {
     }
   }
 
+  V8_INLINE static void MarkPatternAsAssigned(Expression* expression) {}
+
   // Determine if the expression is a variable proxy and mark it as being used
   // in an assignment or with a increment/decrement operator.
   V8_INLINE static void MarkExpressionAsAssigned(Expression* expression) {

src/parsing/preparser.h

@@ -1373,8 +1373,7 @@ class PreParser : public ParserBase<PreParser> {
   V8_INLINE static void CheckAssigningFunctionLiteralToProperty(
       const PreParserExpression& left, const PreParserExpression& right) {}
 
-  V8_INLINE void MarkExpressionAsAssigned(
-      const PreParserExpression& expression) {
+  V8_INLINE void MarkPatternAsAssigned(const PreParserExpression& expression) {
     // TODO(marja): To be able to produce the same errors, the preparser needs
     // to start tracking which expressions are variables and which are assigned.
     if (expression.variables_ != nullptr) {
@@ -1384,6 +1383,15 @@ class PreParser : public ParserBase<PreParser> {
     }
   }
 
+  V8_INLINE void MarkExpressionAsAssigned(
+      const PreParserExpression& expression) {
+    if (IsIdentifier(expression)) {
+      DCHECK_NOT_NULL(expression.variables_);
+      DCHECK_EQ(1, expression.variables_->LengthForTest());
+      expression.variables_->first()->set_is_assigned();
+    }
+  }
+
   V8_INLINE bool ShortcutNumericLiteralBinaryExpression(
       PreParserExpression* x, const PreParserExpression& y, Token::Value op,
       int pos) {
@@ -1416,7 +1424,7 @@ class PreParser : public ParserBase<PreParser> {
   V8_INLINE PreParserStatement InitializeForEachStatement(
       PreParserStatement stmt, const PreParserExpression& each,
       const PreParserExpression& subject, PreParserStatement body) {
-    MarkExpressionAsAssigned(each);
+    MarkPatternAsAssigned(each);
     return stmt;
   }
 
@@ -1425,7 +1433,7 @@ class PreParser : public ParserBase<PreParser> {
       const PreParserExpression& iterable, PreParserStatement body,
       bool finalize, IteratorType type,
       int next_result_pos = kNoSourcePosition) {
-    MarkExpressionAsAssigned(each);
+    MarkPatternAsAssigned(each);
     return stmt;
   }