[destructuring] Refactor duplicate parameter name detection.

Pushed the detection logic down to ParseAndClassifyIdentifier in
preparation to having patterns in parameter positions.

R=arv@chromium.org,rossberg@chromium.org,wingo@igalia.com
BUG=v8:811
LOG=N

Review URL: https://codereview.chromium.org/1170153003

Cr-Commit-Position: refs/heads/master@{#28876}

BUILD.gn

@@ -782,6 +782,7 @@ source_set("v8_base") {
     "src/elements.h",
     "src/execution.cc",
     "src/execution.h",
+    "src/expression-classifier.h",
     "src/extensions/externalize-string-extension.cc",
     "src/extensions/externalize-string-extension.h",
     "src/extensions/free-buffer-extension.cc",

src/parser.cc

@@ -3805,11 +3805,9 @@ void ParserTraits::DeclareArrowFunctionParameters(
   parser_->scope_->RemoveUnresolved(expr->AsVariableProxy());
 
   bool is_rest = false;
-  bool is_duplicate = DeclareFormalParameter(scope, raw_name, is_rest);
-
-  if (is_duplicate && !duplicate_loc->IsValid()) {
-    *duplicate_loc = param_location;
-  }
+  ExpressionClassifier classifier;
+  DeclareFormalParameter(scope, raw_name, &classifier, is_rest);
+  *duplicate_loc = classifier.duplicate_formal_parameter_error().location;
 }
 
 

src/parser.h

@@ -754,19 +754,9 @@ class ParserTraits {
   V8_INLINE Scope* NewScope(Scope* parent_scope, ScopeType scope_type,
                             FunctionKind kind = kNormalFunction);
 
-  bool DeclareFormalParameter(Scope* scope, const AstRawString* name,
-                              bool is_rest) {
-    bool is_duplicate = false;
-    Variable* var = scope->DeclareParameter(name, VAR, is_rest, &is_duplicate);
-    if (is_sloppy(scope->language_mode())) {
-      // TODO(sigurds) Mark every parameter as maybe assigned. This is a
-      // conservative approximation necessary to account for parameters
-      // that are assigned via the arguments array.
-      var->set_maybe_assigned();
-    }
-    return is_duplicate;
-  }
-
+  V8_INLINE void DeclareFormalParameter(Scope* scope, const AstRawString* name,
+                                        ExpressionClassifier* classifier,
+                                        bool is_rest);
   void DeclareArrowFunctionParameters(Scope* scope, Expression* expr,
                                       const Scanner::Location& params_loc,
                                       Scanner::Location* duplicate_loc,
@@ -1282,6 +1272,25 @@ Expression* ParserTraits::SpreadCallNew(
     Expression* function, ZoneList<v8::internal::Expression*>* args, int pos) {
   return parser_->SpreadCallNew(function, args, pos);
 }
+
+
+void ParserTraits::DeclareFormalParameter(Scope* scope,
+                                          const AstRawString* name,
+                                          ExpressionClassifier* classifier,
+                                          bool is_rest) {
+  bool is_duplicate = false;
+  Variable* var = scope->DeclareParameter(name, VAR, is_rest, &is_duplicate);
+  if (is_sloppy(scope->language_mode())) {
+    // TODO(sigurds) Mark every parameter as maybe assigned. This is a
+    // conservative approximation necessary to account for parameters
+    // that are assigned via the arguments array.
+    var->set_maybe_assigned();
+  }
+  if (is_duplicate) {
+    classifier->RecordDuplicateFormalParameterError(
+        parser_->scanner()->location());
+  }
+}
 } }  // namespace v8::internal
 
 #endif  // V8_PARSER_H_

src/preparser.cc

@@ -1033,18 +1033,15 @@ PreParser::Expression PreParser::ParseFunctionLiteral(
   PreParserFactory factory(NULL);
   FunctionState function_state(&function_state_, &scope_, function_scope, kind,
                                &factory);
-  ExpressionClassifier formals_classifier;
+  DuplicateFinder duplicate_finder(scanner()->unicode_cache());
+  ExpressionClassifier formals_classifier(&duplicate_finder);
 
   bool has_rest = false;
   Expect(Token::LPAREN, CHECK_OK);
   int start_position = scanner()->location().beg_pos;
   function_scope->set_start_position(start_position);
-  int num_parameters;
-  {
-    DuplicateFinder duplicate_finder(scanner()->unicode_cache());
-    num_parameters = ParseFormalParameterList(&duplicate_finder, &has_rest,
-                                              &formals_classifier, CHECK_OK);
-  }
+  int num_parameters = ParseFormalParameterList(nullptr, &has_rest,
+                                                &formals_classifier, CHECK_OK);
   Expect(Token::RPAREN, CHECK_OK);
   int formals_end_position = scanner()->location().end_pos;
 

tools/gyp/v8.gyp

@@ -616,6 +616,7 @@
         '../../src/elements.h',
         '../../src/execution.cc',
         '../../src/execution.h',
+        '../../src/expression-classifier.h',
         '../../src/extensions/externalize-string-extension.cc',
         '../../src/extensions/externalize-string-extension.h',
         '../../src/extensions/free-buffer-extension.cc',