[gcc/devel/ranger] c++: Satisfaction caching of inherited ctor [PR94819]

[Aldy Hernandez]

https://gcc.gnu.org/g:1d2290caad0dba52b285b47057b7c0e4e8d21feb

commit 1d2290caad0dba52b285b47057b7c0e4e8d21feb
Author: Patrick Palka <ppalka@redhat.com>
Date:   Tue Apr 28 21:45:59 2020 -0400

    c++: Satisfaction caching of inherited ctor [PR94819]
    
    As observed in PR94719, an inherited constructor for an instantiation of
    a constructor template confusingly has as its DECL_INHERITED_CTOR the
    TEMPLATE_DECL of the constructor template rather than the particular
    instantiation of the template.
    
    This means two inherited constructors for two different instantiations
    of the same constructor template have the same DECL_INHERITED_CTOR.  And
    since in satisfy_declaration_constraints our decl satisfaction cache is
    keyed off of the result of strip_inheriting_ctors, we may end up
    conflating the satisfaction values of the two inherited constructors'
    constraints.
    
    This patch fixes this issue by using the original tree, not the result
    of strip_inheriting_ctors, as the key to the decl satisfaction cache.
    
    gcc/cp/ChangeLog:
    
            PR c++/94819
            * constraint.cc (satisfy_declaration_constraints): Use saved_t
            instead of t as the key to decl_satisfied_cache.
    
    gcc/testsuite/ChangeLog:
    
            PR c++/94819
            * g++.dg/cpp2a/concepts-inherit-ctor10.C: New test.
            * g++.dg/cpp2a/concepts-inherit-ctor11.C: New test.

Diff:
---
 gcc/cp/ChangeLog                                    |  4 ++++
 gcc/cp/constraint.cc                                |  4 ++--
 gcc/testsuite/ChangeLog                             |  4 ++++
 .../g++.dg/cpp2a/concepts-inherit-ctor10.C          | 18 ++++++++++++++++++
 .../g++.dg/cpp2a/concepts-inherit-ctor11.C          | 21 +++++++++++++++++++++
 5 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index c0558015eb8..f2bfe84b1e6 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,9 @@
 2020-04-29  Patrick Palka  <ppalka@redhat.com>
 
+	PR c++/94819
+	* constraint.cc (satisfy_declaration_constraints): Use saved_t
+	instead of t as the key to decl_satisfied_cache.
+
 	PR c++/94808
 	* error.c (print_requires_expression_info): Print the dependent
 	form of the parameter list with its template parameter mapping,
diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 06161b8c8c4..866b0f51b05 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -2752,7 +2752,7 @@ satisfy_declaration_constraints (tree t, subst_info info)
   info.in_decl = t;
 
   if (info.quiet ())
-    if (tree *result = hash_map_safe_get (decl_satisfied_cache, t))
+    if (tree *result = hash_map_safe_get (decl_satisfied_cache, saved_t))
       return *result;
 
   /* Get the normalized constraints.  */
@@ -2787,7 +2787,7 @@ satisfy_declaration_constraints (tree t, subst_info info)
     }
 
   if (info.quiet ())
-    hash_map_safe_put<hm_ggc> (decl_satisfied_cache, t, result);
+    hash_map_safe_put<hm_ggc> (decl_satisfied_cache, saved_t, result);
 
   return result;
 }
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a824ba8424e..512974831c2 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,9 @@
 2020-04-29  Patrick Palka  <ppalka@redhat.com>
 
+	PR c++/94819
+	* g++.dg/cpp2a/concepts-inherit-ctor10.C: New test.
+	* g++.dg/cpp2a/concepts-inherit-ctor11.C: New test.
+
 	PR c++/94808
 	* g++.dg/concepts/diagnostic12.C: New test.
 	* g++.dg/concepts/diagnostic5.C: Adjust dg-message.
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-inherit-ctor10.C b/gcc/testsuite/g++.dg/cpp2a/concepts-inherit-ctor10.C
new file mode 100644
index 00000000000..387c07ae6b2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-inherit-ctor10.C
@@ -0,0 +1,18 @@
+// PR c++/94819
+// { dg-do compile { target concepts } }
+
+struct dna4 {};
+struct rna4 {};
+
+struct alphabet_tuple_base {
+    template <typename component_type>
+        requires __is_same(component_type, rna4)
+    alphabet_tuple_base(component_type) {}
+};
+
+struct structured_rna : alphabet_tuple_base {
+    using alphabet_tuple_base::alphabet_tuple_base;
+};
+
+structured_rna t2{dna4{}}; // { dg-error "no match" }
+structured_rna t3{rna4{}}; // { dg-bogus "no match" }
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-inherit-ctor11.C b/gcc/testsuite/g++.dg/cpp2a/concepts-inherit-ctor11.C
new file mode 100644
index 00000000000..947edd84e53
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-inherit-ctor11.C
@@ -0,0 +1,21 @@
+// PR c++/94819
+// { dg-do compile { target concepts } }
+
+struct dna4 {};
+struct rna4 {};
+
+template <typename component_types>
+struct alphabet_tuple_base {
+    template <typename component_type>
+        requires __is_same(component_type, component_types)
+    alphabet_tuple_base(component_type) {}
+};
+
+template <typename sequence_alphabet_t>
+struct structured_rna : alphabet_tuple_base<sequence_alphabet_t> {
+    using base_type = alphabet_tuple_base<sequence_alphabet_t>;
+    using base_type::base_type;
+};
+
+structured_rna<rna4> t2{dna4{}}; // { dg-error "no match" }
+structured_rna<rna4> t3{rna4{}}; // { dg-bogus "no match" }