c++: nested aggregate/alias CTAD fixes [PR114974, PR114901, PR114903]

During maybe_aggr_guide with a nested class template and paren init,
like with list init we need to consider the generic template type rather
than the partially instantiated type since partial instantiations don't
have (partially instantiated) TYPE_FIELDS.  In turn we need to partially
substitute PARMs in the paren init case as well.  As a drive-by improvement
it seems better to use outer_template_args instead of DECL_TI_ARGS during
this partial substitution so that we lower instead of substitute the
innermost template parameters, which is generally more robust.

And during alias_ctad_tweaks with a nested class template, even though
the guides may be already partially instantiated we still need to
substitute the outermost arguments into its constraints.

	PR c++/114974
	PR c++/114901
	PR c++/114903

gcc/cp/ChangeLog:

	* pt.cc (maybe_aggr_guide): Fix obtaining TYPE_FIELDS in
	the paren init case.  Hoist out partial substitution logic
	to apply to the paren init case as well.
	(alias_ctad_tweaks): Substitute outer template arguments into
	a guide's constraints.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/class-deduction-aggr14.C: New test.
	* g++.dg/cpp2a/class-deduction-alias20.C: New test.
	* g++.dg/cpp2a/class-deduction-alias21.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index a7d9fcf930e2bf6a3d8ae3e5caaf6f9899abcaf0..4b71e199d27f4ceacf4b045a558d61a774cca19a 100644 (file)
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -30194,26 +30194,11 @@ maybe_aggr_guide (tree tmpl, tree init, vec<tree,va_gc> *args)
       if (init == error_mark_node)
        return NULL_TREE;
       parms = collect_ctor_idx_types (init, parms);
-      /* If we're creating a deduction guide for a member class template,
-        we've used the original template pattern type for the reshape_init
-        above; this is done because we want PARMS to be a template parameter
-        type, something that can be deduced when used as a function template
-        parameter.  At this point the outer class template has already been
-        partially instantiated (we deferred the deduction until the enclosing
-        scope is non-dependent).  Therefore we have to partially instantiate
-        PARMS, so that its template level is properly reduced and we don't get
-        mismatches when deducing types using the guide with PARMS.  */
-      if (member_template_p)
-       {
-         ++processing_template_decl;
-         parms = tsubst (parms, DECL_TI_ARGS (tmpl), complain, init);
-         --processing_template_decl;
-       }
     }
   else if (TREE_CODE (init) == TREE_LIST)
     {
       int len = list_length (init);
-      for (tree field = TYPE_FIELDS (type);
+      for (tree field = TYPE_FIELDS (template_type);
           len;
           --len, field = DECL_CHAIN (field))
        {
@@ -30228,6 +30213,22 @@ maybe_aggr_guide (tree tmpl, tree init, vec<tree,va_gc> *args)
     /* Aggregate initialization doesn't apply to an initializer expression.  */
     return NULL_TREE;
 
+  /* If we're creating a deduction guide for a member class template,
+     we've used the original template pattern type for the reshape_init
+     above; this is done because we want PARMS to be a template parameter
+     type, something that can be deduced when used as a function template
+     parameter.  At this point the outer class template has already been
+     partially instantiated (we deferred the deduction until the enclosing
+     scope is non-dependent).  Therefore we have to partially instantiate
+     PARMS, so that its template level is properly reduced and we don't get
+     mismatches when deducing types using the guide with PARMS.  */
+  if (member_template_p)
+    {
+      ++processing_template_decl;
+      parms = tsubst (parms, outer_template_args (tmpl), complain, init);
+      --processing_template_decl;
+    }
+
   if (parms)
     {
       tree last = parms;
@@ -30419,7 +30420,11 @@ alias_ctad_tweaks (tree tmpl, tree uguides)
          /* Substitute the associated constraints.  */
          tree ci = get_constraints (f);
          if (ci)
-           ci = tsubst_constraint_info (ci, targs, complain, in_decl);
+           {
+             if (tree outer_targs = outer_template_args (f))
+               ci = tsubst_constraint_info (ci, outer_targs, complain, in_decl);
+             ci = tsubst_constraint_info (ci, targs, complain, in_decl);
+           }
          if (ci == error_mark_node)
            continue;
 

diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr14.C b/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr14.C
new file mode 100644 (file)
index 0000000..de636eb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-aggr14.C
@@ -0,0 +1,11 @@
+// PR c++/114974
+// { dg-do compile { target c++20 } }
+
+template<typename T1>
+struct A {
+  template<typename T2>
+  struct B { T2 t; };
+};
+
+A<int>::B x{2}; // OK
+A<int>::B y(2); // OK, previously rejected

diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias20.C b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias20.C
new file mode 100644 (file)
index 0000000..8cc56d9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias20.C
@@ -0,0 +1,22 @@
+// PR c++/114901
+// { dg-do compile { target c++20 } }
+
+template <class D>
+constexpr bool C = sizeof(D);
+
+template <typename U>
+struct T {
+  template<typename V, typename N>
+  struct Foo {
+    Foo(V, N);
+  };
+
+  template<typename X, typename N>
+  requires (C<N>) // removes the require-clause will make the crash disappear
+  Foo(X, N) -> Foo<X, N>;
+
+  template <typename Y, typename Y2, int N = sizeof(Y2)>
+  using AFoo = Foo<decltype(N), Y2>;
+};
+
+T<double>::AFoo s{1, 2}; // { dg-error "deduction|no match" }

diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias21.C b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias21.C
new file mode 100644 (file)
index 0000000..c39a0f9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias21.C
@@ -0,0 +1,38 @@
+// PR c++/114903
+// { dg-do compile { target c++20 } }
+
+template <typename T>
+struct Key {
+  Key(int);
+};
+
+class Forward {};
+
+template <typename T>
+constexpr bool C = __is_same(T, Forward);
+
+template <typename Z>
+struct Outer {
+  template <typename U>
+  struct Foo {
+    Foo(U);
+    U u;
+  };
+
+  template <typename V>
+    requires(C<Z>)
+  Foo(V) -> Foo<int>;
+};
+
+template <typename Y>
+struct T {
+  template <typename Y2>
+  struct T2 {
+    template <typename K>
+    using AFoo = Outer<Y2>::template Foo<K>;
+  };
+};
+
+T<Forward>::T2<Forward>::AFoo a(1.0);
+using type = decltype(a);
+using type = Outer<Forward>::Foo<int>;