From b083a14dfe1f53446722f488885078e419238d24 Mon Sep 17 00:00:00 2001
From: Patrick Palka <ppalka@redhat.com>
Date: Thu, 22 Oct 2020 07:27:55 -0400
Subject: 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.
---
gcc/cp/decl.c | 3 +++
gcc/testsuite/g++.dg/template/shadow3.C | 4 ++++
2 files changed, 7 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/template/shadow3.C
(limited to 'gcc')
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 5f370e6..2de4e16 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 0000000..a5f2563
--- /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" }
--
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