c++: static lambda in template [PR108526]

tsubst_lambda_expr uses build_memfn_type to build a METHOD_TYPE for the new
lamba op().  This is not what we want for a C++23 static op(), but since we
also use that METHOD_TYPE to communicate the closure type down to
tsubst_function_decl, let's wait and turn it back at that point.

	PR c++/108526

gcc/cp/ChangeLog:

	* pt.cc (tsubst_function_decl): Handle static lambda.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp23/static-operator-call5.C: New test.

2 files changed, 13 insertions, 0 deletions

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 2a4d03c..51fc246 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -14306,6 +14306,11 @@ tsubst_function_decl (tree t, tree args, tsubst_flags_t complain,
   tree ctx = closure ? closure : DECL_CONTEXT (t);
   bool member = ctx && TYPE_P (ctx);
 
+  /* If this is a static lambda, remove the 'this' pointer added in
+     tsubst_lambda_expr now that we know the closure type.  */
+  if (lambda_fntype && DECL_STATIC_FUNCTION_P (t))
+    lambda_fntype = static_fn_type (lambda_fntype);
+
   if (member && !closure)
     ctx = tsubst_aggr_type (ctx, args,
 			    complain, t, /*entering_scope=*/1);
diff --git a/gcc/testsuite/g++.dg/cpp23/static-operator-call5.C b/gcc/testsuite/g++.dg/cpp23/static-operator-call5.C
new file mode 100644
index 0000000..ae022d0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp23/static-operator-call5.C
@@ -0,0 +1,8 @@
+// PR c++/108526
+// { dg-do compile { target c++23 } }
+
+template<class> void f()
+{
+  auto a = [] (auto x) static { return x; };
+}
+template void f<int>();