c++: error with constexpr operator() [PR107939]
Similarly to PR107938, this also started with r11-557, whereby cp_finish_decl
can call check_initializer even in a template for a constexpr initializer.
Here we are rejecting
extern const Q q;
template<int>
constexpr auto p = q(0);
even though q has a constexpr operator(). It's deemed non-const by
decl_maybe_constant_var_p because even though 'q' is const it is not
of integral/enum type.
If fun is not a function pointer, we don't know if we're using it as an
lvalue or rvalue, so with this patch we pass 'any' for want_rval. With
that, p_c_e/VAR_DECL doesn't flat out reject the underlying VAR_DECL.
PR c++/107939
gcc/cp/ChangeLog:
* constexpr.cc (potential_constant_expression_1) <case CALL_EXPR>: Pass
'any' when recursing on a VAR_DECL and not a pointer to function.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1y/var-templ74.C: Remove dg-error.
* g++.dg/cpp1y/var-templ77.C: New test.