| Message ID | 20210413223601.1413164-1-ppalka@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | c++: Fix deduction with reference NTTP [PR83476] | expand |
On 4/13/21 6:36 PM, Patrick Palka wrote: > In the testcase ref11.C below, during deduction for the call f(a), > uses_deducible_template_parms returns false for the dependent > specialization A<V> because V is wrapped in an implicit INDIRECT_REF > (formed from template_parm_to_arg), and this causes unify_one_argument > to exit early, causing deduction to fail. This patch fixes this > by making deducible_expression look through such implicit INDIRECT_REFs. > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for > trunk? OK. > gcc/cp/ChangeLog: > > PR c++/83476 > PR c++/99885 > * pt.c (deducible_expression): Look through implicit > INDIRECT_REFs as well. > > gcc/testsuite/ChangeLog: > > PR c++/83476 > PR c++/99885 > * g++.dg/cpp1z/class-deduction85.C: New test. > * g++.dg/template/ref11.C: New test. > --- > gcc/cp/pt.c | 6 ++++-- > gcc/testsuite/g++.dg/cpp1z/class-deduction85.C | 16 ++++++++++++++++ > gcc/testsuite/g++.dg/template/ref11.C | 9 +++++++++ > 3 files changed, 29 insertions(+), 2 deletions(-) > create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction85.C > create mode 100644 gcc/testsuite/g++.dg/template/ref11.C > > diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c > index 59df79484bf..f488a5a8c12 100644 > --- a/gcc/cp/pt.c > +++ b/gcc/cp/pt.c > @@ -21902,8 +21902,10 @@ static bool uses_deducible_template_parms (tree type); > static bool > deducible_expression (tree expr) > { > - /* Strip implicit conversions. */ > - while (CONVERT_EXPR_P (expr) || TREE_CODE (expr) == VIEW_CONVERT_EXPR) > + /* Strip implicit conversions and implicit INDIRECT_REFs. */ > + while (CONVERT_EXPR_P (expr) > + || TREE_CODE (expr) == VIEW_CONVERT_EXPR > + || REFERENCE_REF_P (expr)) > expr = TREE_OPERAND (expr, 0); > return (TREE_CODE (expr) == TEMPLATE_PARM_INDEX); > } > diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction85.C b/gcc/testsuite/g++.dg/cpp1z/class-deduction85.C > new file mode 100644 > index 00000000000..0b22f8eb982 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction85.C > @@ -0,0 +1,16 @@ > +// PR c++/99885 > +// { dg-do compile { target c++17 } } > + > +template <auto const& A> > +struct Foo {}; > + > +template <auto const& A> > +struct Bar { > + constexpr auto foo() const -> Foo<A> { > + return {}; > + } > +}; > + > +constexpr int a = 1; > +constexpr Bar<a> bar; > +Foo foo = bar.foo(); // <-- CTAD failure > diff --git a/gcc/testsuite/g++.dg/template/ref11.C b/gcc/testsuite/g++.dg/template/ref11.C > new file mode 100644 > index 00000000000..ef29fb72bef > --- /dev/null > +++ b/gcc/testsuite/g++.dg/template/ref11.C > @@ -0,0 +1,9 @@ > +// PR c++/83476 > + > +template <int& V> struct A {}; > +template <int& V> void f(A<V>); > +int n; > +int main() { > + A<n> a; > + f(a); > +} >
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index 59df79484bf..f488a5a8c12 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -21902,8 +21902,10 @@ static bool uses_deducible_template_parms (tree type); static bool deducible_expression (tree expr) { - /* Strip implicit conversions. */ - while (CONVERT_EXPR_P (expr) || TREE_CODE (expr) == VIEW_CONVERT_EXPR) + /* Strip implicit conversions and implicit INDIRECT_REFs. */ + while (CONVERT_EXPR_P (expr) + || TREE_CODE (expr) == VIEW_CONVERT_EXPR + || REFERENCE_REF_P (expr)) expr = TREE_OPERAND (expr, 0); return (TREE_CODE (expr) == TEMPLATE_PARM_INDEX); } diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction85.C b/gcc/testsuite/g++.dg/cpp1z/class-deduction85.C new file mode 100644 index 00000000000..0b22f8eb982 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction85.C @@ -0,0 +1,16 @@ +// PR c++/99885 +// { dg-do compile { target c++17 } } + +template <auto const& A> +struct Foo {}; + +template <auto const& A> +struct Bar { + constexpr auto foo() const -> Foo<A> { + return {}; + } +}; + +constexpr int a = 1; +constexpr Bar<a> bar; +Foo foo = bar.foo(); // <-- CTAD failure diff --git a/gcc/testsuite/g++.dg/template/ref11.C b/gcc/testsuite/g++.dg/template/ref11.C new file mode 100644 index 00000000000..ef29fb72bef --- /dev/null +++ b/gcc/testsuite/g++.dg/template/ref11.C @@ -0,0 +1,9 @@ +// PR c++/83476 + +template <int& V> struct A {}; +template <int& V> void f(A<V>); +int n; +int main() { + A<n> a; + f(a); +}