| Message ID | 20220330215107.1833323-1-ppalka@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | c++: deduction for dependent class type of NTTP [PR105110] | expand |
On 3/30/22 17:51, Patrick Palka wrote: > Here deduction for the P/A pair V/a spuriously fails with > > types ‘A<T>’ and ‘const A<int>’ have incompatible cv-qualifiers > > because the argument type is const, whereas the parameter type is > non-const. > > Since the type of an NTTP is always cv-unqualified, it seems natural to > ignore cv-qualifiers on the argument type before attempting to unify the > two types. > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for > trunk? OK. > PR c++/105110 > > gcc/cp/ChangeLog: > > * pt.cc (unify) <case TEMPLATE_PARM_INDEX>: Ignore cv-quals on > on the argument type of an NTTP before deducing from it. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp2a/nontype-class52.C: New test. > --- > gcc/cp/pt.cc | 5 +++-- > gcc/testsuite/g++.dg/cpp2a/nontype-class52.C | 13 +++++++++++++ > 2 files changed, 16 insertions(+), 2 deletions(-) > create mode 100644 gcc/testsuite/g++.dg/cpp2a/nontype-class52.C > > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc > index 1acb5990c5c..cdd75d3b6ac 100644 > --- a/gcc/cp/pt.cc > +++ b/gcc/cp/pt.cc > @@ -24271,8 +24271,9 @@ unify (tree tparms, tree targs, tree parm, tree arg, int strict, > && !(strict & UNIFY_ALLOW_INTEGER) > && TEMPLATE_PARM_LEVEL (parm) <= TMPL_ARGS_DEPTH (targs)) > { > - /* Deduce it from the non-type argument. */ > - tree atype = TREE_TYPE (arg); > + /* Deduce it from the non-type argument. As above, ignore > + top-level quals here too. */ > + tree atype = cv_unqualified (TREE_TYPE (arg)); > RECUR_AND_CHECK_FAILURE (tparms, targs, > tparm, atype, > UNIFY_ALLOW_NONE, explain_p); > diff --git a/gcc/testsuite/g++.dg/cpp2a/nontype-class52.C b/gcc/testsuite/g++.dg/cpp2a/nontype-class52.C > new file mode 100644 > index 00000000000..56163376afb > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp2a/nontype-class52.C > @@ -0,0 +1,13 @@ > +// PR c++/105110 > +// { dg-do compile { target c++20 } } > + > +template<class> struct A { }; > + > +template<auto> struct B { }; > + > +template<class T, A<T> V> void f(B<V>); > + > +int main() { > + constexpr A<int> a; > + f(B<a>{}); > +}
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index 1acb5990c5c..cdd75d3b6ac 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -24271,8 +24271,9 @@ unify (tree tparms, tree targs, tree parm, tree arg, int strict, && !(strict & UNIFY_ALLOW_INTEGER) && TEMPLATE_PARM_LEVEL (parm) <= TMPL_ARGS_DEPTH (targs)) { - /* Deduce it from the non-type argument. */ - tree atype = TREE_TYPE (arg); + /* Deduce it from the non-type argument. As above, ignore + top-level quals here too. */ + tree atype = cv_unqualified (TREE_TYPE (arg)); RECUR_AND_CHECK_FAILURE (tparms, targs, tparm, atype, UNIFY_ALLOW_NONE, explain_p); diff --git a/gcc/testsuite/g++.dg/cpp2a/nontype-class52.C b/gcc/testsuite/g++.dg/cpp2a/nontype-class52.C new file mode 100644 index 00000000000..56163376afb --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/nontype-class52.C @@ -0,0 +1,13 @@ +// PR c++/105110 +// { dg-do compile { target c++20 } } + +template<class> struct A { }; + +template<auto> struct B { }; + +template<class T, A<T> V> void f(B<V>); + +int main() { + constexpr A<int> a; + f(B<a>{}); +}