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c++: abstract class and overload resolution

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In my implementation of P0929 I treated a conversion to an rvalue of
abstract class type as a bad conversion, but that's still too soon to check
it; we need to wait until we're done with overload resolution.

gcc/cp/ChangeLog:

	* call.cc (implicit_conversion_1): Rename...
	(implicit_conversion): ...to this.  Remove the old wrapper.

gcc/testsuite/ChangeLog:

	* g++.dg/template/sfinae-dr657.C: Adjust.
This commit is contained in:
Jason Merrill 2023-10-20 16:23:43 -04:00
parent 7d4e991316
commit 55731b59e6
2 changed files with 9 additions and 28 deletions
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30
gcc/cp/call.cc
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@ -2032,12 +2032,14 @@ reference_binding (tree rto, tree rfrom, tree expr, bool c_cast_p, int flags,
return conv;
}
/* Most of the implementation of implicit_conversion, with the same
parameters. */
/* Returns the implicit conversion sequence (see [over.ics]) from type
FROM to type TO. The optional expression EXPR may affect the
conversion. FLAGS are the usual overloading flags. If C_CAST_P is
true, this conversion is coming from a C-style cast. */
static conversion *
implicit_conversion_1 (tree to, tree from, tree expr, bool c_cast_p,
int flags, tsubst_flags_t complain)
implicit_conversion (tree to, tree from, tree expr, bool c_cast_p,
int flags, tsubst_flags_t complain)
{
conversion *conv;
@ -2167,26 +2169,6 @@ implicit_conversion_1 (tree to, tree from, tree expr, bool c_cast_p,
return NULL;
}
/* Returns the implicit conversion sequence (see [over.ics]) from type
FROM to type TO. The optional expression EXPR may affect the
conversion. FLAGS are the usual overloading flags. If C_CAST_P is
true, this conversion is coming from a C-style cast. */
static conversion *
implicit_conversion (tree to, tree from, tree expr, bool c_cast_p,
int flags, tsubst_flags_t complain)
{
conversion *conv = implicit_conversion_1 (to, from, expr, c_cast_p,
flags, complain);
if (!conv || conv->bad_p)
return conv;
if (conv_is_prvalue (conv)
&& CLASS_TYPE_P (conv->type)
&& CLASSTYPE_PURE_VIRTUALS (conv->type))
conv->bad_p = true;
return conv;
}
/* Like implicit_conversion, but return NULL if the conversion is bad.
This is not static so that check_non_deducible_conversion can call it within

7
gcc/testsuite/g++.dg/template/sfinae-dr657.C
View file

@ -1,7 +1,6 @@
// DR 657 SUPERSEDED BY DR 1646
// DR 657 SUPERSEDED BY P0929
// Test that a return or parameter type with abstract class type DOES NOT cause
// a deduction failure, but there is no implicit conversion sequence for
// a parameter of abstract class type.
// a deduction failure or conversion failure.
struct A
{
@ -19,5 +18,5 @@ template<class T> int arg(...);
int main()
{
int i = declval<A>(); // { dg-error "ambiguous" }
i = arg<A>(1);
i = arg<A>(1); // { dg-error "abstract" }
}