Fix parsing of assignment expressions and handling of right-associative

things.

llvm-svn: 38881

clang/Parse/ParseExpr.cpp

@@ -253,15 +253,19 @@ Parser::ParseRHSOfBinaryExpression(ExprResult LHS, unsigned MinPrec) {
     unsigned ThisPrec = NextTokPrec;
     NextTokPrec = getBinOpPrecedence(Tok.getKind());
 
-    // FIXME: ASSIGNMENT IS RIGHT ASSOCIATIVE.
-    // FIXME: do we want to handle assignment here??
-    bool isRightAssoc = OpToken.getKind() == tok::question;
+    // Assignment and conditional expressions are right-associative.
+    bool isRightAssoc = NextTokPrec == prec::Conditional ||
+                        NextTokPrec == prec::Assignment;
 
     // Get the precedence of the operator to the right of the RHS.  If it binds
     // more tightly with RHS than we do, evaluate it completely first.
     if (ThisPrec < NextTokPrec ||
         (ThisPrec == NextTokPrec && isRightAssoc)) {
-      RHS = ParseRHSOfBinaryExpression(RHS, ThisPrec+1);
+      // If this is left-associative, only parse things on the RHS that bind
+      // more tightly than the current operator.  If it is left-associative, it
+      // is okay, to bind exactly as tightly.  For example, compile A=B=C=D as
+      // A=(B=(C=D)), where each paren is a level of recursion here.
+      RHS = ParseRHSOfBinaryExpression(RHS, ThisPrec + !isRightAssoc);
       if (RHS.isInvalid) return RHS;
 
       NextTokPrec = getBinOpPrecedence(Tok.getKind());

clang/test/Parser/statements.c

@@ -62,3 +62,7 @@ void test6() {
 int test7(int a, int b) {
   return a ? a,b : a;
 }
+
+int test8(int a, int b) {
+  return a = b = c;
+}