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* [gcc r10-9743] c++: alias_ctad_tweaks and constrained dguide [PR95486]
@ 2021-04-21 14:27 Patrick Palka
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From: Patrick Palka @ 2021-04-21 14:27 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:4806f9157a26cfd66c083bcc01596ff33009c0d6
commit r10-9743-g4806f9157a26cfd66c083bcc01596ff33009c0d6
Author: Patrick Palka <ppalka@redhat.com>
Date: Wed Jul 29 22:06:41 2020 -0400
c++: alias_ctad_tweaks and constrained dguide [PR95486]
In the below testcase, we're ICEing from alias_ctad_tweaks ultimately
because the implied deduction guide for X's user-defined constructor
already has constraints associated with it. We then carry over these
constraints to 'fprime', the overlying deduction guide for the alias
template Y, via tsubst_decl from alias_ctad_tweaks. Later in
alias_ctad_tweaks we call get_constraints followed by set_constraints
without doing remove_constraints in between, which triggers the !found
assert in set_constraints.
This patch fixes this issue by adding an intervening call to
remove_constraints.
gcc/cp/ChangeLog:
PR c++/95486
* pt.c (alias_ctad_tweaks): Call remove_constraints before
calling set_constraints.
gcc/testsuite/ChangeLog:
PR c++/95486
* g++.dg/cpp2a/class-deduction-alias3.C: New test.
(cherry picked from commit 71141b1bd537cc516e485c834c2d36abba3f4544)
Diff:
---
gcc/cp/pt.c | 5 ++++-
gcc/testsuite/g++.dg/cpp2a/class-deduction-alias3.C | 11 +++++++++++
2 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 76c7e428ecd..ae396e056c5 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -28823,7 +28823,10 @@ alias_ctad_tweaks (tree tmpl, tree uguides)
}
if (ci)
- set_constraints (fprime, ci);
+ {
+ remove_constraints (fprime);
+ set_constraints (fprime, ci);
+ }
}
else
{
diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias3.C b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias3.C
new file mode 100644
index 00000000000..318d4c942ce
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias3.C
@@ -0,0 +1,11 @@
+// PR c++/95486
+// { dg-do compile { target c++20 } }
+
+template<class T, class U>
+struct X { X(U) requires __is_same(U, int) {} };
+
+template<class U>
+using Y = X<void, U>;
+
+Y y{1};
+Y z{'a'}; // { dg-error "failed|no match" }
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