[parsing] When failing due to variable redeclaration, point at the variable.

src/parsing/parser.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_H_
 #define V8_PARSING_PARSER_H_
 
 #include "src/ast/ast.h"
 #include "src/ast/scopes.h"
 #include "src/base/compiler-specific.h"
@@ skipping 450 matching lines @@
 
   // Implement sloppy block-scoped functions, ES2015 Annex B 3.3
   void InsertSloppyBlockFunctionVarBindings(DeclarationScope* scope);
 
   VariableProxy* NewUnresolved(const AstRawString* name, int begin_pos,
                                VariableKind kind = NORMAL_VARIABLE);
   VariableProxy* NewUnresolved(const AstRawString* name);
   Variable* Declare(Declaration* declaration,
                     DeclarationDescriptor::Kind declaration_kind,
                     VariableMode mode, InitializationFlag init, bool* ok,
-                    Scope* declaration_scope = nullptr);
+                    Scope* declaration_scope = nullptr, int var_end_pos = -1);

[adamk, 2016/10/27 10:32:49]

kNoSourcePosition

   Declaration* DeclareVariable(const AstRawString* name, VariableMode mode,
                                int pos, bool* ok);
   Declaration* DeclareVariable(const AstRawString* name, VariableMode mode,
                                InitializationFlag init, int pos, bool* ok);
   Declaration* DeclareModuleImport(const AstRawString* name, int pos, bool* ok);
 
   bool TargetStackContainsLabel(const AstRawString* label);
   BreakableStatement* LookupBreakTarget(const AstRawString* label, bool* ok);
   IterationStatement* LookupContinueTarget(const AstRawString* label, bool* ok);
 
@@ skipping 659 matching lines @@
 
  private:
   ParserTarget** variable_;
   ParserTarget* previous_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_H_