[gcc r16-2147] c++: 'this' in lambda in noexcept-spec [PR121008]

[Jason Merrill via Gcc-cvs]

https://gcc.gnu.org/g:131ba6137bca263d7381ad3331840ee05e306fc9

commit r16-2147-g131ba6137bca263d7381ad3331840ee05e306fc9
Author: Jason Merrill <ja...@redhat.com>
Date:   Wed Jul 9 10:38:20 2025 -0400

    c++: 'this' in lambda in noexcept-spec [PR121008]
    
    In r16-970 I changed finish_this_expr to look at current_class_type rather
    than current_class_ptr to accommodate explicit object lambdas.  But here in
    a lambda in the noexcept-spec, the closure type doesn't yet have the
    function as its context, so lambda_expr_this_capture can't find the function
    and gives up.  But in this context current_class_ptr refers to the
    function's 'this', so let's go back to using it in that case.
    
            PR c++/121008
            PR c++/113563
    
    gcc/cp/ChangeLog:
    
            * semantics.cc (finish_this_expr): Do check current_class_ref for
            non-lambda.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp2a/lambda-uneval28.C: New test.

Diff:
---
 gcc/cp/semantics.cc                          |  8 +++++---
 gcc/testsuite/g++.dg/cpp2a/lambda-uneval28.C | 10 ++++++++++
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 28baf7b3172b..b57547cb8afa 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -3605,11 +3605,13 @@ finish_this_expr (void)
 {
   tree result = NULL_TREE;
 
-  if (current_class_type && LAMBDA_TYPE_P (current_class_type))
+  if (current_class_ref && !LAMBDA_TYPE_P (TREE_TYPE (current_class_ref)))
+    result = current_class_ptr;
+  else if (current_class_type && LAMBDA_TYPE_P (current_class_type))
     result = (lambda_expr_this_capture
              (CLASSTYPE_LAMBDA_EXPR (current_class_type), /*add*/true));
-  else if (current_class_ptr)
-    result = current_class_ptr;
+  else
+    gcc_checking_assert (!current_class_ptr);
 
   if (result)
     /* The keyword 'this' is a prvalue expression.  */
diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-uneval28.C 
b/gcc/testsuite/g++.dg/cpp2a/lambda-uneval28.C
new file mode 100644
index 000000000000..4b1bfc8f0268
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/lambda-uneval28.C
@@ -0,0 +1,10 @@
+// PR c++/121008
+// { dg-do compile { target c++20 } }
+
+struct A {
+  void f()
+    noexcept(noexcept([this]() noexcept(noexcept(this)) {}))
+  {}
+};
+
+int main() {}