[parser,ast] Simplify MarkExpressionAsAssigned.

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 811 matching lines @@
   V8_INLINE static void CheckAssigningFunctionLiteralToProperty(
       Expression* left, Expression* right) {
     DCHECK(left != NULL);
     if (left->IsProperty() && right->IsFunctionLiteral()) {
       right->AsFunctionLiteral()->set_pretenure();
     }
   }
 
   // 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 Expression* MarkExpressionAsAssigned(
-      Expression* expression) {
-    VariableProxy* proxy =
-        expression != NULL ? expression->AsVariableProxy() : NULL;
-    if (proxy != NULL) proxy->set_is_assigned();
-    return expression;
+  V8_INLINE static void MarkExpressionAsAssigned(Expression* expression) {
+    DCHECK_NOT_NULL(expression);
+    if (expression->IsVariableProxy()) {
+      expression->AsVariableProxy()->set_is_assigned();
+    }
   }
 
   // Returns true if we have a binary expression between two numeric
   // literals. In that case, *x will be changed to an expression which is the
   // computed value.
   bool ShortcutNumericLiteralBinaryExpression(Expression** x, Expression* y,
                                               Token::Value op, int pos);
 
   // Rewrites the following types of unary expressions:
   // not <literal> -> true / false
@@ skipping 345 matching lines @@
 
  private:
   ParserTarget** variable_;
   ParserTarget* previous_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_H_