[Bug c++/71718] New: ICE on erroneous recursive template error printing

["denis.campredon at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71718

            Bug ID: 71718
           Summary: ICE on erroneous recursive template error printing
           Product: gcc
           Version: 6.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: denis.campredon at gmail dot com
  Target Milestone: ---

template <typename T>
  class A : T{};

template <typename T>
  using sp = A<T>;

struct Base {};

template <typename T, int num = 1>
const  sp<T>
  rec() 
{
  return rec<T, num - 1>();  
}

static void f(void) {
  rec<Base>();
}
-----------------------
This erroneous code compiled with g++ (6.1.0) produces an ice with the
following backtrace.

--------------------
0x62b536 push_tinst_level_loc(tree_node*, unsigned int)
../../gcc-6.1.0/gcc/cp/pt.c:9077
0x63c942 push_tinst_level(tree_node*)
../../gcc-6.1.0/gcc/cp/pt.c:9061
0x63c942 instantiate_alias_template
../../gcc-6.1.0/gcc/cp/pt.c:17466
0x63c942 tsubst(tree_node*, tree_node*, int, tree_node*)
../../gcc-6.1.0/gcc/cp/pt.c:12842
0x66fef0 dump_template_bindings
../../gcc-6.1.0/gcc/cp/error.c:349
0x66fef0 dump_substitution
../../gcc-6.1.0/gcc/cp/error.c:1450
0x675964 decl_to_string
../../gcc-6.1.0/gcc/cp/error.c:2955
0x675964 cp_printer
../../gcc-6.1.0/gcc/cp/error.c:3535
0x115928c pp_format(pretty_printer*, text_info*)
../../gcc-6.1.0/gcc/pretty-print.c:631
0x1159ff0 pp_format_verbatim(pretty_printer*, text_info*)
../../gcc-6.1.0/gcc/pretty-print.c:690
0x115a0c4 pp_verbatim(pretty_printer*, char const*, ...)
../../gcc-6.1.0/gcc/pretty-print.c:891
0x66f029 print_instantiation_partial_context_line
../../gcc-6.1.0/gcc/cp/error.c:3335
0x66f029 print_instantiation_partial_context
../../gcc-6.1.0/gcc/cp/error.c:3445
0x66f029 print_instantiation_full_context
../../gcc-6.1.0/gcc/cp/error.c:3324
0x66f029 maybe_print_instantiation_context
../../gcc-6.1.0/gcc/cp/error.c:3461
0x67313f cp_diagnostic_starter
../../gcc-6.1.0/gcc/cp/error.c:3154
0x1154e97 diagnostic_report_diagnostic(diagnostic_context*, diagnostic_info*)
../../gcc-6.1.0/gcc/diagnostic.c:824
0x11562a1 fatal_error(unsigned int, char const*, ...)
../../gcc-6.1.0/gcc/diagnostic.c:1239
0x62b536 push_tinst_level_loc(tree_node*, unsigned int)
../../gcc-6.1.0/gcc/cp/pt.c:9077
0x63c942 push_tinst_level(tree_node*)
../../gcc-6.1.0/gcc/cp/pt.c:9061
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.