c++: Tweak tsubst_qualified_id location.

Retain the location when tsubstituting a qualified-id so that our
static_assert diagnostic can benefit.  Don't create useless location
wrappers for temporary variables.

gcc/ChangeLog:

	PR c++/97518
	* tree.c (maybe_wrap_with_location): Don't add a location
	wrapper around an artificial and ignored decl.

gcc/cp/ChangeLog:

	PR c++/97518
	* pt.c (tsubst_qualified_id): Use EXPR_LOCATION of the qualified-id.
	Use it to maybe_wrap_with_location the final expression.

gcc/testsuite/ChangeLog:

	PR c++/97518
	* g++.dg/diagnostic/static_assert3.C: New test.

1 files changed, 4 insertions, 0 deletions

diff --git a/gcc/tree.c b/gcc/tree.c
index 1d4a1da..1ad4ad5 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -15041,6 +15041,10 @@ maybe_wrap_with_location (tree expr, location_t loc)
   if (EXCEPTIONAL_CLASS_P (expr))
     return expr;
 
+  /* Compiler-generated temporary variables don't need a wrapper.  */
+  if (DECL_P (expr) && DECL_ARTIFICIAL (expr) && DECL_IGNORED_P (expr))
+    return expr;
+
   /* If any auto_suppress_location_wrappers are active, don't create
      wrappers.  */
   if (suppress_location_wrappers > 0)