[es6] implement optional parameters via desugaring (with scoping)

src/globals.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_GLOBALS_H_
 #define V8_GLOBALS_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 692 matching lines @@
 
 // Used to specify if a macro instruction must perform a smi check on tagged
 // values.
 enum SmiCheckType {
   DONT_DO_SMI_CHECK,
   DO_SMI_CHECK
 };
 
 
 enum ScopeType {
-  EVAL_SCOPE,      // The top-level scope for an eval source.
-  FUNCTION_SCOPE,  // The top-level scope for a function.
-  MODULE_SCOPE,    // The scope introduced by a module literal
-  SCRIPT_SCOPE,    // The top-level scope for a script or a top-level eval.
-  CATCH_SCOPE,     // The scope introduced by catch.
-  BLOCK_SCOPE,     // The scope introduced by a new block.
-  WITH_SCOPE,      // The scope introduced by with.
-  ARROW_SCOPE      // The top-level scope for an arrow function literal.
+  EVAL_SCOPE,          // The top-level scope for an eval source.
+  FUNCTION_SCOPE,      // The top-level scope for a function.
+  MODULE_SCOPE,        // The scope introduced by a module literal
+  SCRIPT_SCOPE,        // The top-level scope for a script or a top-level eval.
+  CATCH_SCOPE,         // The scope introduced by catch.
+  BLOCK_SCOPE,         // The scope introduced by a new block.
+  WITH_SCOPE,          // The scope introduced by with.
+  ARROW_SCOPE,         // The top-level scope for an arrow function literal.
+  FUNCTION_BODY_SCOPE  // The body of a function
 };
 
 // The mips architecture prior to revision 5 has inverted encoding for sNaN.
 #if (V8_TARGET_ARCH_MIPS && !defined(_MIPS_ARCH_MIPS32R6)) || \
     (V8_TARGET_ARCH_MIPS64 && !defined(_MIPS_ARCH_MIPS64R6))
 const uint32_t kHoleNanUpper32 = 0xFFFF7FFF;
 const uint32_t kHoleNanLower32 = 0xFFFF7FFF;
 #else
 const uint32_t kHoleNanUpper32 = 0xFFF7FFFF;
 const uint32_t kHoleNanLower32 = 0xFFF7FFFF;
@@ skipping 212 matching lines @@
 inline FunctionKind WithObjectLiteralBit(FunctionKind kind) {
   kind = static_cast<FunctionKind>(kind | FunctionKind::kInObjectLiteral);
   DCHECK(IsValidFunctionKind(kind));
   return kind;
 }
 } }  // namespace v8::internal
 
 namespace i = v8::internal;
 
 #endif  // V8_GLOBALS_H_