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c++: Allow defaulted comparison outside class.

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Implementing P2085, another refinement to the operator<=> specification from
the Prague meeting.  It was deemed desirable to be able to have a non-inline
defaulted definition of a comparison operator just like you can with other
defaulted functions.

gcc/cp/ChangeLog:

	* method.c (early_check_defaulted_comparison): Allow defaulting
	comparison outside class.  Complain if non-member operator isn't a
	friend.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/spaceship-friend1.C: New test.
	* g++.dg/cpp2a/spaceship-err4.C: Adjust diagnostic.
This commit is contained in:
Jason Merrill 2020-06-18 17:41:43 -04:00
parent 4cea81adab
commit 4058454c9e
3 changed files with 48 additions and 22 deletions
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38
gcc/cp/method.c
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@ -1102,17 +1102,6 @@ early_check_defaulted_comparison (tree fn)
return false;
}
if (!ctx)
{
if (DECL_OVERLOADED_OPERATOR_IS (fn, SPACESHIP_EXPR))
error_at (loc, "three-way comparison operator can only be defaulted "
"in a class definition");
else
error_at (loc, "equality comparison operator can only be defaulted "
"in a class definition");
return false;
}
if (!DECL_OVERLOADED_OPERATOR_IS (fn, SPACESHIP_EXPR)
&& !same_type_p (TREE_TYPE (TREE_TYPE (fn)), boolean_type_node))
{
@ -1146,16 +1135,27 @@ early_check_defaulted_comparison (tree fn)
for (; parmnode != void_list_node; parmnode = TREE_CHAIN (parmnode))
{
tree parmtype = TREE_VALUE (parmnode);
if (same_type_p (parmtype, ctx))
if (CLASS_TYPE_P (parmtype))
saw_byval = true;
else if (TREE_CODE (parmtype) != REFERENCE_TYPE
|| TYPE_REF_IS_RVALUE (parmtype)
|| TYPE_QUALS (TREE_TYPE (parmtype)) != TYPE_QUAL_CONST
|| !(same_type_ignoring_top_level_qualifiers_p
(TREE_TYPE (parmtype), ctx)))
saw_bad = true;
else if (TREE_CODE (parmtype) == REFERENCE_TYPE
&& !TYPE_REF_IS_RVALUE (parmtype)
&& TYPE_QUALS (TREE_TYPE (parmtype)) == TYPE_QUAL_CONST)
{
saw_byref = true;
parmtype = TREE_TYPE (parmtype);
}
else
saw_byref = true;
saw_bad = true;
if (!saw_bad && !ctx)
{
/* Defaulted outside the class body. */
ctx = TYPE_MAIN_VARIANT (parmtype);
if (!is_friend (ctx, fn))
error_at (loc, "defaulted %qD is not a friend of %qT", fn, ctx);
}
else if (!same_type_ignoring_top_level_qualifiers_p (parmtype, ctx))
saw_bad = true;
}
if (saw_bad || (saw_byval && saw_byref))

6
gcc/testsuite/g++.dg/cpp2a/spaceship-err4.C
View File

@ -2,6 +2,6 @@
// { dg-do compile { target c++20 } }
struct B {};
bool operator!=(const B&, const B&) = default; // { dg-error "equality comparison operator can only be defaulted in a class definition" }
bool operator==(const B&, const B&) = default; // { dg-error "equality comparison operator can only be defaulted in a class definition" }
bool operator<=>(const B&, const B&) = default; // { dg-error "three-way comparison operator can only be defaulted in a class definition" }
bool operator!=(const B&, const B&) = default; // { dg-error "not a friend" }
bool operator==(const B&, const B&) = default; // { dg-error "not a friend" }
bool operator<=>(const B&, const B&) = default; // { dg-error "not a friend" }

26
gcc/testsuite/g++.dg/cpp2a/spaceship-friend1.C Normal file
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@ -0,0 +1,26 @@
// P2085, separate definition of defaulted comparisons
// { dg-do compile { target c++20 } }
namespace X {
struct A {
int i;
friend constexpr bool operator==(const A&,const A&);
};
inline constexpr bool operator==(const A&,const A&)=default;
static_assert (A() == A());
}
namespace Y {
struct A {
int i;
// friend bool operator==(const A&,const A&);
};
inline bool operator==(const A&,const A&)=default; // { dg-error "not a friend" }
}