Message ID | 65e7e72a.050a0220.d77d9.6e86@mx.google.com |
---|---|
State | New |
Headers | show |
Series | [v2] c++: Fix template deduction for conversion operators with xobj parameters [PR113629] | expand |
On 3/5/24 22:46, Nathaniel Shead wrote: > On Tue, Mar 05, 2024 at 06:19:07PM -0500, Jason Merrill wrote: >> On 3/5/24 17:47, Nathaniel Shead wrote: >>> Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk? >>> >>> -- >8 -- >>> >>> Unification for conversion operators (DEDUCE_CONV) doesn't perform >>> transformations like handling forwarding references. This is correct in >>> general, but not for xobj parameters, which should be handled "normally" >>> for the purposes of deduction: [temp.deduct.conv] only applies to the >>> return type of the conversion function. >>> >>> PR c++/113629 >>> >>> gcc/cp/ChangeLog: >>> >>> * pt.cc (type_unification_real): Use DEDUCE_CALL for xobj >>> parameters of conversion functions. >>> >>> gcc/testsuite/ChangeLog: >>> >>> * g++.dg/cpp23/explicit-obj-conv-op.C: New test. >>> >>> Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com> >>> --- >>> gcc/cp/pt.cc | 15 +++++- >>> .../g++.dg/cpp23/explicit-obj-conv-op.C | 49 +++++++++++++++++++ >>> 2 files changed, 63 insertions(+), 1 deletion(-) >>> create mode 100644 gcc/testsuite/g++.dg/cpp23/explicit-obj-conv-op.C >>> >>> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc >>> index c4bc54a8fdb..632437d3424 100644 >>> --- a/gcc/cp/pt.cc >>> +++ b/gcc/cp/pt.cc >>> @@ -23281,6 +23281,10 @@ type_unification_real (tree tparms, >>> in TARGS. */ >>> NON_DEFAULT_TEMPLATE_ARGS_COUNT (targs) = NULL_TREE; >>> + bool is_xobj_conv_fn >>> + = (strict == DEDUCE_CONV >>> + && DECL_XOBJ_MEMBER_FUNCTION_P (TREE_TYPE (tparms))); >>> + >>> again: >>> parms = xparms; >>> args = xargs; >>> @@ -23312,10 +23316,17 @@ type_unification_real (tree tparms, >>> parameter pack is a non-deduced context. */ >>> continue; >>> + /* For explicit object parameters, unification should behave like >>> + normal function calls, even for conversion functions. This >>> + corresponds to the second (that is, last) argument. */ >>> + unification_kind_t kind = strict; >>> + if (is_xobj_conv_fn && ia > 0) >> >> Is it necessary to check the xobj flag? Or can this just be >> >> if (strict == DEDUCE_CONV && ia > 0) >> >> ? >> >> Jason >> > > I restricted it to xobj to be conservative, but I think you're right > that it's not necessary: there's nothing special about xobj here apart > from this being a new circumstance where we might actually need to unify > the object parameter. > > Here's a new version of the patch. Bootstrapped and regtested (so far > only dg.exp) on x86_64-pc-linux-gnu, OK for trunk if full regtest > completes successfully? OK. > -- >8 -- > > Unification for conversion operators (DEDUCE_CONV) doesn't perform > transformations like handling forwarding references. This is correct in > general, but not for xobj parameters, which should be handled "normally" > for the purposes of deduction: [temp.deduct.conv] only applies to the > return type of the conversion function. > > PR c++/113629 > > gcc/cp/ChangeLog: > > * pt.cc (type_unification_real): Only use DEDUCE_CONV for the > return type of a conversion function. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp23/explicit-obj-conv-op.C: New test. > > Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com> > --- > gcc/cp/pt.cc | 12 ++++- > .../g++.dg/cpp23/explicit-obj-conv-op.C | 49 +++++++++++++++++++ > 2 files changed, 60 insertions(+), 1 deletion(-) > create mode 100644 gcc/testsuite/g++.dg/cpp23/explicit-obj-conv-op.C > > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc > index c4bc54a8fdb..a6e6c804130 100644 > --- a/gcc/cp/pt.cc > +++ b/gcc/cp/pt.cc > @@ -23312,10 +23312,18 @@ type_unification_real (tree tparms, > parameter pack is a non-deduced context. */ > continue; > > + /* [temp.deduct.conv] only applies to the deduction of the return > + type, which is always the first argument here. Other arguments > + (notably, explicit object parameters) should undergo normal > + call-like unification. */ > + unification_kind_t kind = strict; > + if (strict == DEDUCE_CONV && ia > 0) > + kind = DEDUCE_CALL; > + > arg = args[ia]; > ++ia; > > - if (unify_one_argument (tparms, full_targs, parm, arg, subr, strict, > + if (unify_one_argument (tparms, full_targs, parm, arg, subr, kind, > explain_p)) > return 1; > } > @@ -23324,6 +23332,8 @@ type_unification_real (tree tparms, > && parms != void_list_node > && TREE_CODE (TREE_VALUE (parms)) == TYPE_PACK_EXPANSION) > { > + gcc_assert (strict != DEDUCE_CONV); > + > /* Unify the remaining arguments with the pack expansion type. */ > tree argvec; > tree parmvec = make_tree_vec (1); > diff --git a/gcc/testsuite/g++.dg/cpp23/explicit-obj-conv-op.C b/gcc/testsuite/g++.dg/cpp23/explicit-obj-conv-op.C > new file mode 100644 > index 00000000000..a6ae4ea1dda > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp23/explicit-obj-conv-op.C > @@ -0,0 +1,49 @@ > +// PR c++/113629 > +// { dg-do compile { target c++23 } } > + > +template <typename T> constexpr bool is_lvalue = false; > +template <typename T> constexpr bool is_lvalue<T&> = true; > + > +struct A { > + constexpr operator bool(this auto&& self) { > + return is_lvalue<decltype(self)>; > + } > +}; > + > +constexpr A a; > +static_assert(static_cast<bool>(a)); > +static_assert((bool)a); > +static_assert(!static_cast<bool>(A{})); > +static_assert(!(bool)A{}); > + > +struct B : A {}; > + > +constexpr B b; > +static_assert(static_cast<bool>(b)); > +static_assert((bool)b); > +static_assert(!static_cast<bool>(B{})); > +static_assert(!(bool)B{}); > + > +struct C { > + template <typename R, typename T> > + explicit constexpr operator R(this T&&) { > + return is_lvalue<T>; > + } > +}; > + > +constexpr C c; > +static_assert(static_cast<bool>(c)); > +static_assert((bool)c); > +static_assert(!static_cast<bool>(C{})); > +static_assert(!(bool)C{}); > + > +struct D { > + explicit constexpr operator bool(this const D&) { return true; } > + explicit constexpr operator bool(this const D&&) { return false; } > +}; > + > +constexpr D d; > +static_assert(static_cast<bool>(d)); > +static_assert((bool)d); > +static_assert(!static_cast<bool>(D{})); > +static_assert(!(bool)D{});
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index c4bc54a8fdb..a6e6c804130 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -23312,10 +23312,18 @@ type_unification_real (tree tparms, parameter pack is a non-deduced context. */ continue; + /* [temp.deduct.conv] only applies to the deduction of the return + type, which is always the first argument here. Other arguments + (notably, explicit object parameters) should undergo normal + call-like unification. */ + unification_kind_t kind = strict; + if (strict == DEDUCE_CONV && ia > 0) + kind = DEDUCE_CALL; + arg = args[ia]; ++ia; - if (unify_one_argument (tparms, full_targs, parm, arg, subr, strict, + if (unify_one_argument (tparms, full_targs, parm, arg, subr, kind, explain_p)) return 1; } @@ -23324,6 +23332,8 @@ type_unification_real (tree tparms, && parms != void_list_node && TREE_CODE (TREE_VALUE (parms)) == TYPE_PACK_EXPANSION) { + gcc_assert (strict != DEDUCE_CONV); + /* Unify the remaining arguments with the pack expansion type. */ tree argvec; tree parmvec = make_tree_vec (1); diff --git a/gcc/testsuite/g++.dg/cpp23/explicit-obj-conv-op.C b/gcc/testsuite/g++.dg/cpp23/explicit-obj-conv-op.C new file mode 100644 index 00000000000..a6ae4ea1dda --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp23/explicit-obj-conv-op.C @@ -0,0 +1,49 @@ +// PR c++/113629 +// { dg-do compile { target c++23 } } + +template <typename T> constexpr bool is_lvalue = false; +template <typename T> constexpr bool is_lvalue<T&> = true; + +struct A { + constexpr operator bool(this auto&& self) { + return is_lvalue<decltype(self)>; + } +}; + +constexpr A a; +static_assert(static_cast<bool>(a)); +static_assert((bool)a); +static_assert(!static_cast<bool>(A{})); +static_assert(!(bool)A{}); + +struct B : A {}; + +constexpr B b; +static_assert(static_cast<bool>(b)); +static_assert((bool)b); +static_assert(!static_cast<bool>(B{})); +static_assert(!(bool)B{}); + +struct C { + template <typename R, typename T> + explicit constexpr operator R(this T&&) { + return is_lvalue<T>; + } +}; + +constexpr C c; +static_assert(static_cast<bool>(c)); +static_assert((bool)c); +static_assert(!static_cast<bool>(C{})); +static_assert(!(bool)C{}); + +struct D { + explicit constexpr operator bool(this const D&) { return true; } + explicit constexpr operator bool(this const D&&) { return false; } +}; + +constexpr D d; +static_assert(static_cast<bool>(d)); +static_assert((bool)d); +static_assert(!static_cast<bool>(D{})); +static_assert(!(bool)D{});