[gcc r11-10100] c++: dependent generic lambda template-id [PR106024]

[Jason Merrill]

https://gcc.gnu.org/g:252e9dfee9b1d01e0e44773ad83e0e44f3650945

commit r11-10100-g252e9dfee9b1d01e0e44773ad83e0e44f3650945
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Jun 23 23:14:35 2022 -0400

    c++: dependent generic lambda template-id [PR106024]
    
    We were wrongly looking up the generic lambda op() in a dependent scope, and
    then trying to look up its instantiation at substitution time, but lambdas
    aren't instantiated, so we crashed.  The fix is to not look into dependent
    lambda scopes.
    
            PR c++/106024
    
    gcc/cp/ChangeLog:
    
            * parser.c (cp_parser_lookup_name): Don't look in dependent lambda.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp2a/lambda-generic10.C: New test.

Diff:
---
 gcc/cp/parser.c                               |  5 ++++-
 gcc/testsuite/g++.dg/cpp2a/lambda-generic10.C | 14 ++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index b53cc6d360e..94b10922b90 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -29434,9 +29434,12 @@ cp_parser_lookup_name (cp_parser *parser, tree name,
     }
   else if (object_type)
     {
+      bool dep = dependent_scope_p (object_type);
+
       /* Look up the name in the scope of the OBJECT_TYPE, unless the
 	 OBJECT_TYPE is not a class.  */
-      if (CLASS_TYPE_P (object_type))
+      if (CLASS_TYPE_P (object_type)
+	  && !(dep && LAMBDA_TYPE_P (object_type)))
 	/* If the OBJECT_TYPE is a template specialization, it may
 	   be instantiated during name lookup.  In that case, errors
 	   may be issued.  Even if we rollback the current tentative
diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-generic10.C b/gcc/testsuite/g++.dg/cpp2a/lambda-generic10.C
new file mode 100644
index 00000000000..773fb948cee
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/lambda-generic10.C
@@ -0,0 +1,14 @@
+// PR c++/106024
+// { dg-do compile { target c++20 } }
+
+void sink(...);
+template <int... args> void f()
+{
+  sink ([] <int T> (int...) { return 1; }
+        .operator()<args>(args...)...); // { dg-error "" }
+} // { dg-prune-output {expected '\)'} }
+
+int main()
+{
+  f<1,2,3>();
+}