Leftover expressions for ODR use checking after fatal error (if you ignore them)

[azat]

Summary

Using simple source code:

$ cat /tmp/string.cpp                                                                                                                                                                                                                                                             
#include <string>
int main()
{
        std::string a("a");
        a = std::to_string((float)1);
        return a.length();
}

With clang::ASTFrontendAction::ExecuteAction() the next assertion bails:

/src/oss/clang/lib/Sema/SemaDecl.cpp:10637: clang::Decl* clang::Sema::ActOnFinishFunctionBody(clang::Decl*, clang::Stmt*, bool): Assertion `MaybeODRUseExprs.empty() && "Leftover expressions for odr-use checking"' failed.

But if I compile the same source using clang++ everything is fine, because size_t is defined there, while if I use ASTFrontendAction size_t is not defined, and if you will ignore errors, than it will bail in ActOnFinishFunctionBody().

Anyway, I've digged this, and got simple regression test for this.
I guess that this could be not the correct fix, but this how I fixed this in a few days.

http://lists.cs.uiuc.edu/pipermail/cfe-dev/2015-February/041726.html

lib/Parse/ParseExpr.cpp

              })) {
             (void)Actions.CorrectDelayedTyposInExpr(LHS);
             LHS = ExprError();
+            Actions.DiscardCleanupsInEvaluationContext();
           }
         }
       }