c++: mangle multiple levels of template parms [PR109422]

This becomes be more important with concepts, but can also be seen with
generic lambdas.

	PR c++/109422

gcc/cp/ChangeLog:

	* mangle.cc (write_template_param): Also mangle level.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/lambda-generic-mangle1.C: New test.
	* g++.dg/cpp2a/lambda-generic-mangle1a.C: New test.

1 files changed, 13 insertions, 0 deletions

diff --git a/gcc/cp/mangle.cc b/gcc/cp/mangle.cc
index d88c779..d079f72 100644
--- a/gcc/cp/mangle.cc
+++ b/gcc/cp/mangle.cc
@@ -3921,6 +3921,7 @@ static void
 write_template_param (const tree parm)
 {
   int parm_index;
+  int level;
 
   MANGLE_TRACE_TREE ("template-parm", parm);
 
@@ -3930,10 +3931,12 @@ write_template_param (const tree parm)
     case TEMPLATE_TEMPLATE_PARM:
     case BOUND_TEMPLATE_TEMPLATE_PARM:
       parm_index = TEMPLATE_TYPE_IDX (parm);
+      level = TEMPLATE_TYPE_LEVEL (parm);
       break;
 
     case TEMPLATE_PARM_INDEX:
       parm_index = TEMPLATE_PARM_IDX (parm);
+      level = TEMPLATE_PARM_LEVEL (parm);
       break;
 
     default:
@@ -3941,6 +3944,16 @@ write_template_param (const tree parm)
     }
 
   write_char ('T');
+  if (level > 1)
+    {
+      if (abi_warn_or_compat_version_crosses (19))
+	G.need_abi_warning = 1;
+      if (abi_version_at_least (19))
+	{
+	  write_char ('L');
+	  write_compact_number (level - 1);
+	}
+    }
   /* NUMBER as it appears in the mangling is (-1)-indexed, with the
      earliest template param denoted by `_'.  */
   write_compact_number (parm_index);