[Bug c++/95927] ICE in cp_lexer_new_from_tokens, at cp/parser.c:701

["haoxintu at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95927

--- Comment #1 from Haoxin Tu <haoxintu at gmail dot com> ---
Add a more meaningful case.


$cat p.cc
template <class> struct a {};
class A {
    struct a < struct x { void b ( ){}} >;
};

$g++ p.cc
p.cc:3:25: error: types may not be defined in template arguments
    3 |     struct a < struct x { void b ( ){}} >;
      |                         ^
p.cc:3:40: error: expected ‘;’ after struct definition
    3 |     struct a < struct x { void b ( ){}} >;
      |                                        ^
      |                                        ;
p.cc:3:39: error: expected template-argument before ‘;’ token
    3 |     struct a < struct x { void b ( ){}} >;
      |                                       ^
p.cc:3:39: error: expected ‘>’ before ‘;’ token
p.cc:3:5: error: ‘struct a<A::x>’ redeclared with different access
    3 |     struct a < struct x { void b ( ){}} >;
      |     ^~~~~~
p.cc:3:41: error: expected unqualified-id before ‘>’ token
    3 |     struct a < struct x { void b ( ){}} >;
      |                                         ^
p.cc:4:1: internal compiler error: in cp_lexer_new_from_tokens, at
cp/parser.c:701
    4 | };
      | ^
0x6adadc cp_parser_push_lexer_for_tokens
        ../../gcc/cp/parser.c:701
...


While in Clang
$clang++ p.cc
p.cc:3:23: error: 'x' cannot be defined in a type specifier
    struct a < struct x { void b ( ){}} >;
                      ^
1 error generated.

I guess Clang is performed better when parsing this case. GCC emits a lot of
error messages even throw an ICE, while Clang just emits one.