c++: lambda in concept [PR105652]

We currently check satisfaction in the context of the constrained
declaration (which may be wrong, see PR104111).  When checking C<int>
for S<int>, we currently substitute into the lambda in the context of
S<T> (rather than S<int>, which seems wrong if the above isn't wrong), so
the new closure type thinks its context is S<T>, which confuses debug
output.  For the moment, let's work around all of this by overriding the
context of the closure.

	PR c++/105652

gcc/cp/ChangeLog:

	* pt.cc (tsubst_lambda_expr): Don't let a namespace-scope lambda
	instantiate into a class-scope lambda.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/concepts-lambda20.C: New test.

1 files changed, 12 insertions, 5 deletions

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 24bbe2f..f1f0805 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -19740,11 +19740,18 @@ tsubst_lambda_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
     return error_mark_node;
 
   if (LAMBDA_EXPR_EXTRA_SCOPE (t) == NULL_TREE)
-    /* A lambda in a default argument outside a class gets no
-       LAMBDA_EXPR_EXTRA_SCOPE, as specified by the ABI.  But
-       tsubst_default_argument calls start_lambda_scope, so we need to
-       specifically ignore it here, and use the global scope.  */
-    record_null_lambda_scope (r);
+    {
+      /* A lambda in a default argument outside a class gets no
+	 LAMBDA_EXPR_EXTRA_SCOPE, as specified by the ABI.  But
+	 tsubst_default_argument calls start_lambda_scope, so we need to
+	 specifically ignore it here, and use the global scope.  */
+      record_null_lambda_scope (r);
+
+      /* If we're pushed into another scope (PR105652), fix it.  */
+      if (TYPE_NAMESPACE_SCOPE_P (TREE_TYPE (t)))
+	TYPE_CONTEXT (type) = DECL_CONTEXT (TYPE_NAME (type))
+	  = TYPE_CONTEXT (TREE_TYPE (t));
+    }
   else
     record_lambda_scope (r);