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C++ PATCH for c++/60182 (alias-decl and template template parameter)

Message ID 530E1DC2.8030102@redhat.com
State New
Headers show

Commit Message

Jason Merrill Feb. 26, 2014, 5 p.m. UTC 
We can never deduce an alias-template for a template template parameter, 
so we should look through aliases when doing TTP deduction.

Tested x86_64-pc-linux-gnu, applying to trunk and eventually 4.8.
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Patch

commit 6fdb7f6d1c186b42adf078ebc5a9b409197a0e69
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Feb 26 10:28:56 2014 -0500

    	PR c++/60182
    	* pt.c (unify): Ignore alias templates when deducing a template
    	template parameter.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 4a9fa71..d723311 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -17390,9 +17390,11 @@  unify (tree tparms, tree targs, tree parm, tree arg, int strict,
 	  if (TREE_CODE (arg) != BOUND_TEMPLATE_TEMPLATE_PARM
 	      && !CLASSTYPE_SPECIALIZATION_OF_PRIMARY_TEMPLATE_P (arg))
 	    return unify_template_deduction_failure (explain_p, parm, arg);
-
 	  {
 	    tree parmvec = TYPE_TI_ARGS (parm);
+	    /* An alias template name is never deduced.  */
+	    if (TYPE_ALIAS_P (arg))
+	      arg = strip_typedefs (arg);
 	    tree argvec = INNERMOST_TEMPLATE_ARGS (TYPE_TI_ARGS (arg));
 	    tree full_argvec = add_to_template_args (targs, argvec);
 	    tree parm_parms 
diff --git a/gcc/testsuite/g++.dg/cpp0x/alias-decl-41.C b/gcc/testsuite/g++.dg/cpp0x/alias-decl-41.C
new file mode 100644
index 0000000..c444217
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/alias-decl-41.C
@@ -0,0 +1,18 @@ 
+// PR c++/60182
+// { dg-require-effective-target c++11 }
+
+class B {};
+template <typename> using __allocator_base = B;
+template <typename> class F : __allocator_base<int> {};
+class C {};
+template <typename, typename = F<int> > class G : C {};
+template <typename> class D;
+class A {
+  using Container = G<D<char>>;
+  A();
+  A(D<char> const &);
+  Container m_elements;
+};
+template <template <class, class> class C, class A = F<D<int>>>
+void doSomething(C<D<char>, A> &);
+A::A(D<char> const &) : A() { doSomething(m_elements); }