https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94592
--- Comment #10 from CVS Commits ---
The master branch has been updated by Marek Polacek :
https://gcc.gnu.org/g:d419e176d74162af6513be0b3bc1031726543993
commit r10-7836-gd419e176d74162af6513be0b3bc1031726543993
Author: Marek Polacek
Date: Fri Apr 17 15:47:15 2020 -0400
c++: Fix ICE with { } as template argument [PR94592]
As an extension (there should be a CWG about this though), we support
braced-init-list as a template argument, but convert_nontype_argument
had trouble digesting them. We ICEd because of the double coercion we
perform for template arguments: convert_nontype_argument called from
finish_template_type got a { }, and since a class type was involved and
we were in a template, convert_like created an IMPLICIT_CONV_EXPR. Then
the second conversion of the same argument crashed in constexpr.c
because the IMPLICIT_CONV_EXPR had gotten wrapped in a TARGET_EXPR.
Another issue was that an IMPLICIT_CONV_EXPR leaked to constexpr.c when
building an aggregate init.
We should have instantiated the IMPLICIT_CONV_EXPR in the first call to
convert_nontype_argument, but we didn't, because the call to
is_nondependent_constant_expression returned false because it checks
!BRACE_ENCLOSED_INITIALIZER_P. Then non_dep was false even though the
expression didn't contain anything dependent and we didn't instantiate
it in convert_nontype_argument. To fix this, check
BRACE_ENCLOSED_INITIALIZER_P in cxx_eval_outermost_constant_expr rather
than in is_nondependent_*.
PR c++/94592
* constexpr.c (cxx_eval_outermost_constant_expr): Return when T is
a BRACE_ENCLOSED_INITIALIZER_P.
(is_nondependent_constant_expression): Don't check
BRACE_ENCLOSED_INITIALIZER_P.
(is_nondependent_static_init_expression): Likewise.
* g++.dg/cpp2a/nontype-class34.C: New test.
* g++.dg/cpp2a/nontype-class35.C: New test.
