[COMMITTED] c++: Fix ICE with constrained friend (PR93400).
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Message ID 20200125060853.9501-1-jason@redhat.com
State New
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  • [COMMITTED] c++: Fix ICE with constrained friend (PR93400).
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Commit Message

Jason Merrill Jan. 25, 2020, 6:08 a.m. UTC
Here, the problem was that tsubst_friend_function was modifying the
CONSTRAINT_INFO for the friend template to have the constraints for one
instantiation, which fell down when we went to adjust it for another
instantiation.  Fixed by deferring substitution of trailing requirements
until we try to check declaration matching.

Tested x86_64-pc-linux-gnu, applying to trunk.

	PR c++/93400 - ICE with constrained friend.
	* constraint.cc (maybe_substitute_reqs_for): New.
	* decl.c (function_requirements_equivalent_p): Call it.
	* pt.c (tsubst_friend_function): Only substitute
	TEMPLATE_PARMS_CONSTRAINTS.
	(tsubst_template_parms): Copy constraints.
---
 gcc/cp/cp-tree.h                              |  1 +
 gcc/cp/constraint.cc                          | 23 ++++++++++++++
 gcc/cp/decl.c                                 |  2 ++
 gcc/cp/pt.c                                   | 31 +++++--------------
 gcc/testsuite/g++.dg/cpp2a/concepts-friend3.C |  3 ++
 gcc/testsuite/g++.dg/cpp2a/concepts-friend5.C |  8 +++++
 gcc/testsuite/g++.dg/cpp2a/concepts-pr84140.C |  5 ++-
 7 files changed, 47 insertions(+), 26 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-friend5.C


base-commit: 8b91e848130e45b427599ad30e99f96e447ea9aa

Patch
diff mbox series

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 77bcf046608..b8035b4360d 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7832,6 +7832,7 @@  extern void remove_constraints                  (tree);
 extern tree current_template_constraints	(void);
 extern tree associate_classtype_constraints     (tree);
 extern tree build_constraints                   (tree, tree);
+extern tree maybe_substitute_reqs_for		(tree, const_tree);
 extern tree get_template_head_requirements	(tree);
 extern tree get_trailing_function_requirements	(tree);
 extern tree get_shorthand_constraints           (tree);
diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 823604afb89..cda644eabe2 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -1189,6 +1189,29 @@  remove_constraints (tree t)
     decl_constraints->remove (t);
 }
 
+/* If DECL is a friend, substitute into REQS to produce requirements suitable
+   for declaration matching.  */
+
+tree
+maybe_substitute_reqs_for (tree reqs, const_tree decl_)
+{
+  if (reqs == NULL_TREE)
+    return NULL_TREE;
+  tree decl = CONST_CAST_TREE (decl_);
+  tree result = STRIP_TEMPLATE (decl);
+  if (DECL_FRIEND_P (result))
+    {
+      tree tmpl = decl == result ? DECL_TI_TEMPLATE (result) : decl;
+      tree gargs = generic_targs_for (tmpl);
+      processing_template_decl_sentinel s;
+      if (uses_template_parms (gargs))
+	++processing_template_decl;
+      reqs = tsubst_constraint (reqs, gargs,
+				tf_warning_or_error, NULL_TREE);
+    }
+  return reqs;
+}
+
 /* Returns the template-head requires clause for the template
    declaration T or NULL_TREE if none.  */
 
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 98ed79f3579..e55de5dd53d 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -942,6 +942,8 @@  function_requirements_equivalent_p (tree newfn, tree oldfn)
   tree reqs2 = get_trailing_function_requirements (oldfn);
   if ((reqs1 != NULL_TREE) != (reqs2 != NULL_TREE))
     return false;
+  reqs1 = maybe_substitute_reqs_for (reqs1, newfn);
+  reqs2 = maybe_substitute_reqs_for (reqs2, oldfn);
   return cp_tree_equal (reqs1, reqs2);
 }
 
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 209044135cb..45c204e4269 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -10834,29 +10834,12 @@  tsubst_friend_function (tree decl, tree args)
       DECL_SAVED_TREE (DECL_TEMPLATE_RESULT (new_friend))
 	= DECL_SAVED_TREE (DECL_TEMPLATE_RESULT (decl));
 
-      /* Attach the template requirements to the new declaration
-         for declaration matching. We need to rebuild the requirements
-         so that parameter levels match.  */
-      if (tree ci = get_constraints (decl))
-	{
-	  tree parms = DECL_TEMPLATE_PARMS (new_friend);
-	  tree args = generic_targs_for (new_friend);
-	  tree treqs = tsubst_constraint (CI_TEMPLATE_REQS (ci), args,
-					  tf_warning_or_error, NULL_TREE);
-	  tree freqs = tsubst_constraint (CI_DECLARATOR_REQS (ci), args,
-					  tf_warning_or_error, NULL_TREE);
-
-	  /* Update the constraints -- these won't really be valid for
-	     checking, but that's not what we need them for. These ensure
-	     that the declared function can find the friend during
-	     declaration matching.  */
-	  tree new_ci = get_constraints (new_friend);
-	  CI_TEMPLATE_REQS (new_ci) = treqs;
-	  CI_DECLARATOR_REQS (new_ci) = freqs;
-
-	  /* Also update the template parameter list.  */
-	  TEMPLATE_PARMS_CONSTRAINTS (parms) = treqs;
-	}
+      /* Substitute TEMPLATE_PARMS_CONSTRAINTS so that parameter levels will
+	 match in decls_match.  */
+      tree parms = DECL_TEMPLATE_PARMS (new_friend);
+      tree treqs = TEMPLATE_PARMS_CONSTRAINTS (parms);
+      treqs = maybe_substitute_reqs_for (treqs, new_friend);
+      TEMPLATE_PARMS_CONSTRAINTS (parms) = treqs;
     }
 
   /* The mangled name for the NEW_FRIEND is incorrect.  The function
@@ -13225,6 +13208,8 @@  tsubst_template_parms (tree parms, tree args, tsubst_flags_t complain)
 	tree_cons (size_int (TMPL_PARMS_DEPTH (parms)
 			     - TMPL_ARGS_DEPTH (args)),
 		   new_vec, NULL_TREE);
+      TEMPLATE_PARMS_CONSTRAINTS (*new_parms)
+	= TEMPLATE_PARMS_CONSTRAINTS (parms);
     }
 
   --processing_template_decl;
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-friend3.C b/gcc/testsuite/g++.dg/cpp2a/concepts-friend3.C
index 4f49358ed7d..4278278b9df 100644
--- a/gcc/testsuite/g++.dg/cpp2a/concepts-friend3.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-friend3.C
@@ -4,6 +4,7 @@  template <class T> concept True = true;
 
 template <True U> struct B { int i = ++U::x; };
 template <True U> void f() { ++U::x; }
+template <class U> void g() requires True<U> { ++U::x; }
 
 template <class V> class C
 {
@@ -11,10 +12,12 @@  template <class V> class C
 
   template <True U> friend struct B;
   template <True U> friend void f();
+  template <class U> friend void g() requires True<U>;
 };
 
 int main()
 {
   f<C<int>>();
+  g<C<int>>();
   B<C<int>>();
 }
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-friend5.C b/gcc/testsuite/g++.dg/cpp2a/concepts-friend5.C
new file mode 100644
index 00000000000..394f141bf17
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-friend5.C
@@ -0,0 +1,8 @@ 
+// PR c++/93400
+// { dg-do compile { target concepts } }
+
+template <typename> bool a = true;
+template <typename i> concept b = a<i>;
+template <int> struct f { template <b c> friend auto g(c, f); };
+auto d = f<1>{};
+auto e = f<0>{};
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-pr84140.C b/gcc/testsuite/g++.dg/cpp2a/concepts-pr84140.C
index d901ab20cbf..83a9083cf17 100644
--- a/gcc/testsuite/g++.dg/cpp2a/concepts-pr84140.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-pr84140.C
@@ -1,14 +1,13 @@ 
 // { dg-do run { target c++2a } }
-// { dg-additional-options "-fconcepts-ts" }
 
 template<class, class> constexpr bool is_same_v = false;
 template<class T> constexpr bool is_same_v<T, T> = true;
 
 template<class T, class U>
-concept bool Same = is_same_v<T, U>;
+concept Same = is_same_v<T, U>;
 
 template<class T, class U>
-concept bool Diff = requires(T& t, U& u) { u - t; };
+concept Diff = requires(T& t, U& u) { u - t; };
 
 template<class I, class S>
 int distance(I, S) { return 0; }