From: Patrick Palka <ppalka@redhat.com>
Date: Thu, 22 Oct 2020 11:27:55 +0000 (-0400)
Subject: c++: Check DECL_TEMPLATE_PARM_P in duplicate_decls [PR97511]
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=b083a14dfe1f53446722f488885078e419238d24;p=gcc.git

c++: Check DECL_TEMPLATE_PARM_P in duplicate_decls [PR97511]

This makes duplicate_decls differentiate a TYPE_DECL for an alias
template from a TYPE_DECL for one of its template parameters.  The
recently added assert in template_parm_to_arg revealed this latent issue
because merging of the two TYPE_DECLs cleared the DECL_TEMPLATE_PARM_P
flag.

With this patch, we now also correctly diagnose the name shadowing in
the below testcase (as required by [temp.local]/6).

gcc/cp/ChangeLog:

	PR c++/97511
	* decl.c (duplicate_decls): Return NULL_TREE if
	DECL_TEMPLATE_PARM_P differ.

gcc/testsuite/ChangeLog:

	PR c++/97511
	* g++.dg/template/shadow3.C: New test.
---

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 5f370e60b4e..2de4e1657fb 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -2002,6 +2002,9 @@ duplicate_decls (tree newdecl, tree olddecl, bool hiding, bool was_hidden)
 	  || DECL_IMPLICIT_TYPEDEF_P (newdecl)))
     return NULL_TREE;
 
+  if (DECL_TEMPLATE_PARM_P (olddecl) != DECL_TEMPLATE_PARM_P (newdecl))
+    return NULL_TREE;
+
   if (!validate_constexpr_redeclaration (olddecl, newdecl))
     return error_mark_node;
 
diff --git a/gcc/testsuite/g++.dg/template/shadow3.C b/gcc/testsuite/g++.dg/template/shadow3.C
new file mode 100644
index 00000000000..a5f256384ac
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/shadow3.C
@@ -0,0 +1,4 @@
+// PR c++/97511
+// { dg-do compile { target c++11 } }
+
+template <class Z> using Z = Z; // { dg-error "shadow|declaration" }