Fix bug in compound assignment detection.

ICSharpCode.Decompiler/IL/Transforms/ExpressionTransforms.cs

@@ -204,8 +204,9 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			IField f, f2;
 			ILInstruction t, t2, a, a2;
 			IType type, type2;
+			ILVariable v;
 			if (target.MatchLdFlda(out t, out f) && left.MatchLdFlda(out t2, out f2) && f.Equals(f2))
-				return true;
+				return !t.MatchLdLoc(out v) || t2.MatchLdLoc(v);
 			// match ldelmena(ldobj(...))
 			if (target.MatchLdElema(out type, out a) && left.MatchLdElema(out type2, out a2) && type.Equals(type2))
 				return a.MatchLdObj(out target, out type) && a2.MatchLdObj(out left, out type2) && IsSameTarget(target, left);