Re: [PATCH] c++: ICE with unnamed tparm and concept [PR103408]

[Jason Merrill via Gcc-patches]

On 12/1/21 10:16, Marek Polacek wrote:

Here we crash when issuing the "constraint C has type T, not bool"
error, because pp_cxx_parameter_mapping wasn't prepared to see an
anonymous template parameter.  With this patch we print

error: constraint 'auto(<lambda>) [with <unnamed> = 0]' has type '<lambda()>', 
not 'bool'

The "<unnamed>" is what this patch adds.

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

OK.

        PR c++/103408

gcc/cp/ChangeLog:

        * cxx-pretty-print.c (pp_cxx_parameter_mapping): Print "<unnamed>"
        rather than crash on an unnamed template parameter.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp23/concepts-err1.C: New test.
---
  gcc/cp/cxx-pretty-print.c                  | 4 +++-
  gcc/testsuite/g++.dg/cpp23/concepts-err1.C | 6 ++++++
  2 files changed, 9 insertions(+), 1 deletion(-)
  create mode 100644 gcc/testsuite/g++.dg/cpp23/concepts-err1.C

diff --git a/gcc/cp/cxx-pretty-print.c b/gcc/cp/cxx-pretty-print.c
index 25cabfee39f..3ea357deb80 100644
--- a/gcc/cp/cxx-pretty-print.c
+++ b/gcc/cp/cxx-pretty-print.c
@@ -2891,8 +2891,10 @@ pp_cxx_parameter_mapping (cxx_pretty_printer *pp, tree 
map)

if (TYPE_P (parm))

        pp->type_id (parm);
+      else if (tree name = DECL_NAME (TEMPLATE_PARM_DECL (parm)))
+       pp_cxx_tree_identifier (pp, name);
        else
-       pp_cxx_tree_identifier (pp, DECL_NAME (TEMPLATE_PARM_DECL (parm)));
+       pp->translate_string ("<unnamed>");

pp_cxx_whitespace (pp);

        pp_equal (pp);
diff --git a/gcc/testsuite/g++.dg/cpp23/concepts-err1.C 
b/gcc/testsuite/g++.dg/cpp23/concepts-err1.C
new file mode 100644
index 00000000000..e5bdc542bad
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp23/concepts-err1.C
@@ -0,0 +1,6 @@
+// PR c++/103408
+// { dg-do compile { target c++23 } }
+
+template<int>
+concept C = auto([]{}); // { dg-error "constraint" }
+static_assert(C<0>); // { dg-error "non-constant condition for static 
assertion" }

base-commit: 6b8ecbc6d6652d061d7c72c64352d51eca2df6ca