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C++ PATCH for c++/84785, ICE with alias template and default targs

Message ID CADzB+2mX3ty9x5zo-1rFPe9a_g6_55WA7jWcK7GgvxnLp2Wodw@mail.gmail.com
State New
Headers show
Series C++ PATCH for c++/84785, ICE with alias template and default targs | expand

Commit Message

Jason Merrill March 10, 2018, 3:31 a.m. UTC 
If we are missing some earlier template arguments, we need to be
prepared for template parameters to remain in the result of
substitution.  In such a situation we need to make sure
processing_template_decl is set so things don't get confused by those
template parameters.

Tested x86_64-pc-linux-gnu, applying to trunk/7/6.
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Patch

commit c7c6394b812ab2dcdace68d637c516ea3fb2a5f5
Author: Jason Merrill <jason@redhat.com>
Date:   Fri Mar 9 17:40:39 2018 -0500

            PR c++/84785 - ICE with alias template and default targs.
    
            * pt.c (type_unification_real): Set processing_template_decl if
            saw_undeduced == 1.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 89024c10fe2..2d7ce6062a7 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -19977,7 +19977,13 @@  type_unification_real (tree tparms,
 	  location_t save_loc = input_location;
 	  if (DECL_P (parm))
 	    input_location = DECL_SOURCE_LOCATION (parm);
+
+	  if (saw_undeduced == 1)
+	    ++processing_template_decl;
 	  arg = tsubst_template_arg (arg, full_targs, fcomplain, NULL_TREE);
+	  if (saw_undeduced == 1)
+	    --processing_template_decl;
+
 	  if (arg != error_mark_node && !uses_template_parms (arg))
 	    arg = convert_template_argument (parm, arg, full_targs, complain,
 					     i, NULL_TREE);
diff --git a/gcc/testsuite/g++.dg/cpp0x/alias-decl-63.C b/gcc/testsuite/g++.dg/cpp0x/alias-decl-63.C
new file mode 100644
index 00000000000..04fb42d9e09
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/alias-decl-63.C
@@ -0,0 +1,18 @@ 
+// PR c++/84785
+// { dg-do compile { target c++11 } }
+
+template <typename> struct A;
+template <bool> struct B;
+template <bool B, typename> using enable_if_t = typename B<B>::type;
+template <long> using type_pack_element = int;
+struct variant {
+  variant() {}
+  template <typename Arg, long I = Arg::type::value,
+            typename = type_pack_element<I>, enable_if_t<A<Arg>::value, int>>
+  variant(Arg &&);
+};
+
+struct S {
+  variant var;
+};
+int main() { S s; }