[PATCH] c++: ICE with erroneous template redeclaration [PR106311]

[Marek Polacek via Gcc-patches]

Here we ICE trying to get DECL_SOURCE_LOCATION of the parm that happens
to be error_mark_node in this ill-formed test.  I kept running into this
while reducing code, so it'd be good to have it fixed.

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

        PR c++/106311

gcc/cp/ChangeLog:

        * pt.cc (redeclare_class_template): Check DECL_P before accessing
        DECL_SOURCE_LOCATION.

gcc/testsuite/ChangeLog:

        * g++.dg/template/redecl5.C: New test.
---
 gcc/cp/pt.cc                            | 3 ++-
 gcc/testsuite/g++.dg/template/redecl5.C | 5 +++++
 2 files changed, 7 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/template/redecl5.C

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 718dfa5bfa8..0a294e91a79 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -6377,7 +6377,8 @@ redeclare_class_template (tree type, tree parms, tree 
cons)
        {
          auto_diagnostic_group d;
          error ("template parameter %q+#D", tmpl_parm);
-         inform (DECL_SOURCE_LOCATION (parm), "redeclared here as %q#D", parm);
+         inform (DECL_P (parm) ? DECL_SOURCE_LOCATION (parm) : input_location,
+                 "redeclared here as %q#D", parm);
          return false;
        }
 
diff --git a/gcc/testsuite/g++.dg/template/redecl5.C 
b/gcc/testsuite/g++.dg/template/redecl5.C
new file mode 100644
index 00000000000..fb2d698e6bc
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/redecl5.C
@@ -0,0 +1,5 @@
+// PR c++/106311
+// { dg-do compile }
+
+template <typename, long> struct array; // { dg-error "template parameter" }
+template <typename, size_t X> struct array { }; // { dg-error "declared" }

base-commit: 23dd41c480fa9f06c33c1e6090bbae53869f85af
-- 
2.36.1