Replace a dyn_cast with a cast when we know the exact type

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@58330 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index f330444..b2cf6ad 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -398,7 +398,7 @@
     //   A function call is an lvalue if and only if the result type
     //   is a reference.
     QualType CalleeType 
-      = dyn_cast<CallExpr>(this)->getCallee()->IgnoreParens()->getType();
+      = cast<CallExpr>(this)->getCallee()->IgnoreParens()->getType();
     if (const PointerType *FnTypePtr = CalleeType->getAsPointerType())
       if (const FunctionType *FnType
             = FnTypePtr->getPointeeType()->getAsFunctionType())