[gcc/devel/c++-coroutines] c++: Fix ICE in check_local_shadow with enum [PR95560]

[Iain D Sandoe]

https://gcc.gnu.org/g:2661635323bd44410f1a154683eccecd2c163b46

commit 2661635323bd44410f1a154683eccecd2c163b46
Author: Marek Polacek <polacek@redhat.com>
Date:   Tue Jun 16 13:02:23 2020 -0400

    c++: Fix ICE in check_local_shadow with enum [PR95560]
    
    Another indication that perhaps this warning is emitted too early.  We
    crash because same_type_p gets a null type: we have an enumerator
    without a fixed underlying type and finish_enum_value_list hasn't yet
    run.  So check if the type is null before calling same_type_p.
    
            PR c++/95560
            * name-lookup.c (check_local_shadow): Check if types are
            non-null before calling same_type_p.
    
            * g++.dg/warn/Wshadow-local-3.C: New test.

Diff:
---
 gcc/cp/name-lookup.c                        | 4 +++-
 gcc/testsuite/g++.dg/warn/Wshadow-local-3.C | 7 +++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index 2ff85f1cf5e..159c98a67cd 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -2762,7 +2762,9 @@ check_local_shadow (tree decl)
       enum opt_code warning_code;
       if (warn_shadow)
 	warning_code = OPT_Wshadow;
-      else if (same_type_p (TREE_TYPE (old), TREE_TYPE (decl))
+      else if ((TREE_TYPE (old)
+		&& TREE_TYPE (decl)
+		&& same_type_p (TREE_TYPE (old), TREE_TYPE (decl)))
 	       || TREE_CODE (decl) == TYPE_DECL
 	       || TREE_CODE (old) == TYPE_DECL
 	       || (!dependent_type_p (TREE_TYPE (decl))
diff --git a/gcc/testsuite/g++.dg/warn/Wshadow-local-3.C b/gcc/testsuite/g++.dg/warn/Wshadow-local-3.C
new file mode 100644
index 00000000000..fd743eca347
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wshadow-local-3.C
@@ -0,0 +1,7 @@
+// PR c++/95560
+// { dg-do compile { target c++11 } }
+
+template <typename> void fn1() {
+  bool ready;
+  enum class State { ready };
+}