c++: Fix canonical type for lambda pack captures [PR122015]

comp_template_parms_position uses whether a TEMPLATE_TYPE_PARM is a pack
to determine equivalency.  This in turn affects whether
canonical_type_parameter finds a pre-existing auto type as equivalent.

When generating the 'auto...' type for a lambda pack capture, we only
mark it as a pack after generating the node (and calculating its
canonical); this means that later when comparing a version streamed in
from a module we think that two equivalent types have different
TYPE_CANONICAL, because the latter already had
TEMPLATE_PARM_PARAMETER_PACK set before calculating its canonical.

This patch fixes this by using a new 'make_auto_pack' function to ensure
that packness is set before the canonical is looked up.

	PR c++/122015

gcc/cp/ChangeLog:

	* cp-tree.h (make_auto_pack): Declare.
	* lambda.cc (lambda_capture_field_type): Use make_auto_pack to
	ensure TYPE_CANONICAL is set correctly.
	* pt.cc (make_auto_pack): New function.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/lambda-11.h: New test.
	* g++.dg/modules/lambda-11_a.H: New test.
	* g++.dg/modules/lambda-11_b.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
Reviewed-by: Patrick Palka <ppalka@redhat.com>

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index d531bcd833b3028213242bc534fb142718c944fc..54156cb0d237d6d64ceef036236190fa9ef4e3c1 100644 (file)
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7835,6 +7835,7 @@ extern tree make_constrained_auto         (tree, tree);
 extern tree make_constrained_decltype_auto     (tree, tree);
 extern tree make_template_placeholder          (tree);
 extern tree make_cast_auto                     (void);
+extern tree make_auto_pack                     (void);
 extern bool template_placeholder_p             (tree);
 extern bool ctad_template_p                    (tree);
 extern bool unparenthesized_id_or_class_member_access_p (tree);

diff --git a/gcc/cp/lambda.cc b/gcc/cp/lambda.cc
index bb0aa7d0a020f174f2f096e9b44c3a1bfc4e6196..575daaa9d711f80ba1fd6bd7bfdb72d2d8c72b89 100644 (file)
--- a/gcc/cp/lambda.cc
+++ b/gcc/cp/lambda.cc
@@ -220,18 +220,23 @@ lambda_capture_field_type (tree expr, bool explicit_init_p,
 
   if (explicit_init_p)
     {
-      tree auto_node = make_auto ();
-
-      type = auto_node;
-      if (by_reference_p)
-       /* Add the reference now, so deduction doesn't lose
-          outermost CV qualifiers of EXPR.  */
-       type = build_reference_type (type);
       if (uses_parameter_packs (expr))
-       /* Stick with 'auto' even if the type could be deduced.  */
-       TEMPLATE_TYPE_PARAMETER_PACK (auto_node) = true;
+       {
+         /* Stick with 'auto...' even if the type could be deduced.  */
+         type = make_auto_pack ();
+         if (by_reference_p)
+           type = build_reference_type (type);
+       }
       else
-       type = do_auto_deduction (type, expr, auto_node);
+       {
+         tree auto_node = make_auto ();
+         type = auto_node;
+         if (by_reference_p)
+           /* Add the reference now, so deduction doesn't lose
+              outermost CV qualifiers of EXPR.  */
+           type = build_reference_type (type);
+         type = do_auto_deduction (type, expr, auto_node);
+       }
     }
   else if (!type_deducible_expression_p (expr))
     {

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 494b6be7a24081a1f6e736ae9bca09df6bce8e71..06287f0b04525e798a36b0ea64970497d7464c89 100644 (file)
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -30493,6 +30493,18 @@ make_constrained_decltype_auto (tree con, tree args)
   return make_constrained_placeholder_type (type, con, args);
 }
 
+/* Create an "auto..." type-specifier.  */
+
+tree
+make_auto_pack ()
+{
+  tree type = make_auto_1 (auto_identifier, false);
+  TEMPLATE_TYPE_PARAMETER_PACK (type) = true;
+  /* Our canonical type depends on being a pack.  */
+  TYPE_CANONICAL (type) = canonical_type_parameter (type);
+  return type;
+}
+
 /* Returns true if the placeholder type constraint T has any dependent
    (explicit) template arguments.  */
 

diff --git a/gcc/testsuite/g++.dg/modules/lambda-11.h b/gcc/testsuite/g++.dg/modules/lambda-11.h
new file mode 100644 (file)
index 0000000..e4a07f2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/lambda-11.h
@@ -0,0 +1,6 @@
+// PR c++/122015
+
+template <typename> auto declval();
+template <typename... _BindArgs> void bind_front() {
+  [... __bound_args(_BindArgs{})] {};
+}

diff --git a/gcc/testsuite/g++.dg/modules/lambda-11_a.H b/gcc/testsuite/g++.dg/modules/lambda-11_a.H
new file mode 100644 (file)
index 0000000..03d0242
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/lambda-11_a.H
@@ -0,0 +1,6 @@
+// PR c++/122015
+// { dg-do compile { target c++20 } }
+// { dg-additional-options "-fmodule-header" }
+// { dg-module-cmi {} }
+
+#include "lambda-11.h"

diff --git a/gcc/testsuite/g++.dg/modules/lambda-11_b.C b/gcc/testsuite/g++.dg/modules/lambda-11_b.C
new file mode 100644 (file)
index 0000000..c7a5f43
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/lambda-11_b.C
@@ -0,0 +1,6 @@
+// PR c++/122015
+// { dg-do compile { target c++20 } }
+// { dg-additional-options "-fmodules -fno-module-lazy" }
+
+#include "lambda-11.h"
+import "lambda-11_a.H";