[gcc r12-3235] c++: preserve location through constexpr

[gcc r12-3235] c++: preserve location through constexpr

[Jason Merrill]

https://gcc.gnu.org/g:729f6881cfcc6df3c15a1dd4ebd45bc46bb8f3e9

commit r12-3235-g729f6881cfcc6df3c15a1dd4ebd45bc46bb8f3e9
Author: Jason Merrill <jason@redhat.com>
Date:   Sat Aug 28 00:40:29 2021 -0400

    c++: preserve location through constexpr
    
    While working on the patch for PR101460, I noticed that we were losing the
    expression location when folding class prvalue expressions.  The final patch
    doesn't fold class prvalues, but this still seems a worthwhile change.  I
    don't add location wrappers for scalar prvalues because many callers are
    trying to fold them away.
    
    gcc/cp/ChangeLog:
    
            * constexpr.c (cxx_eval_outermost_constant_expr): Copy
            expr location to result.

Diff:
---
 gcc/cp/constexpr.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 9606719bc73..e78fdf021b2 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -7445,6 +7445,11 @@ cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant,
 	}
     }
 
+  /* Remember the original location if that wouldn't need a wrapper.  */
+  if (location_t loc = EXPR_LOCATION (t))
+    if (CAN_HAVE_LOCATION_P (r))
+      SET_EXPR_LOCATION (r, loc);
+
   return r;
 }