From 46c72915f43a5d10537ef5986444078664fb7265 Mon Sep 17 00:00:00 2001
From: Steve Naroff <snaroff@apple.com>
Date: Sat, 25 Aug 2007 19:54:59 +0000
Subject: [PATCH] Surpress the UsualUnaryConversions for compound assignment
 operators. This change eliminates the possibility that the left hand
 expression is an ImplicitCastExpr. As a result, I removed the check for
 ImplicitCastExpr in Expr::isLvalue().

This results in the following AST's...

[dylan:~/llvm/tools/clang] admin% cat fix.c

short x; void test4(char c) {
  x += c;
  x = x + c;
}
[dylan:~/llvm/tools/clang] admin% ../../Debug/bin/clang fix.c -parse-ast-dump
Read top-level variable decl: 'x'

void test4(char c)
(CompoundStmt 0x2605d30
  (CompoundAssignOperator 0x2605c40 'short' '+='
    (DeclRefExpr 0x2605c00 'short' Decl='x' 0x2605a80)
    (DeclRefExpr 0x2605c20 'char' Decl='c' 0x2605bc0))
  (BinaryOperator 0x2605d10 'short' '='
    (DeclRefExpr 0x2605c60 'short' Decl='x' 0x2605a80)
    (ImplicitCastExpr 0x2605d00 'short'
      (BinaryOperator 0x2605ce0 'int' '+'
        (ImplicitCastExpr 0x2605cc0 'int'
          (DeclRefExpr 0x2605c80 'short' Decl='x' 0x2605a80))
        (ImplicitCastExpr 0x2605cd0 'int'
          (DeclRefExpr 0x2605ca0 'char' Decl='c' 0x2605bc0))))))

llvm-svn: 41404
---
 clang/AST/Expr.cpp      | 2 --
 clang/Sema/SemaExpr.cpp | 7 ++++---
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/clang/AST/Expr.cpp b/clang/AST/Expr.cpp
index 5167d4e109b3..535e1ef786f1 100644
--- a/clang/AST/Expr.cpp
+++ b/clang/AST/Expr.cpp
@@ -302,8 +302,6 @@ Expr::isLvalueResult Expr::isLvalue() const {
     if (cast<OCUVectorElementExpr>(this)->containsDuplicateElements())
       return LV_DuplicateVectorComponents;
     return LV_Valid;
-  case ImplicitCastExprClass: // A side-effect of our implementation.
-    return cast<ImplicitCastExpr>(this)->getSubExpr()->isLvalue();
   default:
     break;
   }
diff --git a/clang/Sema/SemaExpr.cpp b/clang/Sema/SemaExpr.cpp
index a86a25525646..7666ad0474d4 100644
--- a/clang/Sema/SemaExpr.cpp
+++ b/clang/Sema/SemaExpr.cpp
@@ -765,9 +765,10 @@ void Sema::UsualUnaryConversions(Expr *&expr) {
 /// responsible for emitting appropriate error diagnostics.
 QualType Sema::UsualArithmeticConversions(Expr *&lhsExpr, Expr *&rhsExpr,
                                           bool isCompAssign) {
-  UsualUnaryConversions(lhsExpr);
-  UsualUnaryConversions(rhsExpr);
-  
+  if (!isCompAssign) {
+    UsualUnaryConversions(lhsExpr);
+    UsualUnaryConversions(rhsExpr);
+  }
   QualType lhs = lhsExpr->getType();
   QualType rhs = rhsExpr->getType();