diff options
| author | Patrick Palka <ppalka@redhat.com> | 2021-04-14 08:54:30 -0400 |
|---|---|---|
| committer | Patrick Palka <ppalka@redhat.com> | 2022-05-11 08:30:29 -0400 |
| commit | c6432e17960799509c48df6b500a8d069110980b (patch) | |
| tree | a194c8955a03d076400204af883641d03d28d048 | |
| parent | d042fa8e2cfabe5da83634ce05e8130d1010c034 (diff) | |
c++: Fix deduction with reference NTTP [PR83476]
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 the generic template argument V here is
wrapped in an implicit INDIRECT_REF (formed from template_parm_to_arg).
Since uses_deducible_template_parms returns false, unify_one_argument
exits early without ever attempting to deduce 'n' for 'V'. This patch
fixes this by making deducible_expression look through such implicit
INDIRECT_REFs.
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.
(cherry picked from commit 2ccc05a5141506fde0e20dec702c717fd67bf6ee)
| -rw-r--r-- | gcc/cp/pt.c | 6 | ||||
| -rw-r--r-- | gcc/testsuite/g++.dg/cpp1z/class-deduction85.C | 16 | ||||
| -rw-r--r-- | gcc/testsuite/g++.dg/template/ref11.C | 9 |
3 files changed, 29 insertions, 2 deletions
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index 612557bb717..08909e2c863 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -20824,8 +20824,10 @@ 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..c43c67edf70 --- /dev/null +++ b/gcc/testsuite/g++.dg/template/ref11.C @@ -0,0 +1,9 @@ +// PR c++/83476 + +int n; +template <int& V> struct A {}; +template <int& V> void f(A<V>); +int main() { + A<n> a; + f(a); +} |