fix(cpp1): emit correct UFCS in function signature

regression-tests/mixed-bugfix-for-ufcs-non-local.cpp2

@@ -0,0 +1,25 @@
+template<bool> struct t { };
+constexpr bool f(const t<true>&) { return true; }
+constexpr t<true> o{};
+
+// Variables.
+
+// _: <V: t<o.f()>> bool = (); // Blocked on #389, [GCC109781][].
+
+_: t<o.f()> = ();
+
+_: bool = o.f();
+
+// Functions.
+
+// g: <V: t<o.f()>> () = { } // Blocked on [GCC109781][].
+
+g: (x: t<o.f()>) = { }
+
+g: () [[pre: o.f()]] = { }
+
+h: () -> t<o.f()> = o;
+
+main: () = { }
+
+// [GCC109781]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109781

regression-tests/pure2-bugfix-for-ufcs-sfinae.cpp2

@@ -0,0 +1,5 @@
+f: <T> () -> std::type_identity_t<decltype(T().a())> = { }
+B: type                                              = { }
+main: ()                                             = {
+  static_assert(!std::invocable<decltype(:<T> (x: T) -> std::void_t<decltype(f<T>())> = {}), B>);
+}

regression-tests/test-results/mixed-bugfix-for-ufcs-non-local.cpp

@@ -0,0 +1,59 @@
+
+
+//=== Cpp2 type declarations ====================================================
+
+
+#include "cpp2util.h"
+
+
+
+//=== Cpp2 type definitions and function declarations ===========================
+
+template<bool> struct t { };
+constexpr bool f(const t<true>&) { return true; }
+constexpr t<true> o{};
+
+// Variables.
+
+// _: <V: t<o.f()>> bool = (); // Blocked on #389, [GCC109781][].
+
+#line 9 "mixed-bugfix-for-ufcs-non-local.cpp2"
+extern t<CPP2_UFCS(,,(f),(o),())> auto_9_1;
+
+extern bool auto_11_1;
+
+// Functions.
+
+// g: <V: t<o.f()>> () = { } // Blocked on [GCC109781][].
+
+auto g(cpp2::in<t<CPP2_UFCS(,,(f),(o),())>> x) -> void;
+
+auto g() -> void;
+
+[[nodiscard]] auto h() -> t<CPP2_UFCS(,,(f),(o),())>;
+
+auto main() -> int;
+
+// [GCC109781]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109781
+
+
+//=== Cpp2 function definitions =================================================
+
+
+#line 9 "mixed-bugfix-for-ufcs-non-local.cpp2"
+t<CPP2_UFCS(,,(f),(o),())> auto_9_1 {}; 
+
+bool auto_11_1 {CPP2_UFCS(,,(f),(o),())}; 
+
+#line 17 "mixed-bugfix-for-ufcs-non-local.cpp2"
+auto g(cpp2::in<t<CPP2_UFCS(,,(f),(o),())>> x) -> void{}
+
+auto g() -> void{
+                         cpp2::Default.expects(CPP2_UFCS(&,,(f),(o),()), "");
+#line 19 "mixed-bugfix-for-ufcs-non-local.cpp2"
+}
+
+[[nodiscard]] auto h() -> t<CPP2_UFCS(,,(f),(o),())> { return o;  }
+
+auto main() -> int{}
+

regression-tests/test-results/mixed-bugfix-for-ufcs-non-local.cpp2.output

@@ -0,0 +1,2 @@
+mixed-bugfix-for-ufcs-non-local.cpp2... ok (mixed Cpp1/Cpp2, Cpp2 code passes safety checks)
+

regression-tests/test-results/pure2-bugfix-for-ufcs-sfinae.cpp

@@ -0,0 +1,36 @@
+
+#define CPP2_USE_MODULES         Yes
+
+//=== Cpp2 type declarations ====================================================
+
+
+#include "cpp2util.h"
+
+
+#line 2 "pure2-bugfix-for-ufcs-sfinae.cpp2"
+class B;
+
+
+//=== Cpp2 type definitions and function declarations ===========================
+
+#line 1 "pure2-bugfix-for-ufcs-sfinae.cpp2"
+template<typename T> [[nodiscard]] auto f() -> std::type_identity_t<decltype(CPP2_UFCS(,,(a),(T()),()))>;
+class B                                               {
+      public: B() = default;
+      public: B(B const&) = delete; /* No 'that' constructor, suppress copy */
+      public: auto operator=(B const&) -> void = delete;
+
+#line 2 "pure2-bugfix-for-ufcs-sfinae.cpp2"
+                                                         };
+auto main() -> int;
+
+
+//=== Cpp2 function definitions =================================================
+
+#line 1 "pure2-bugfix-for-ufcs-sfinae.cpp2"
+template<typename T> [[nodiscard]] auto f() -> std::type_identity_t<decltype(CPP2_UFCS(,,(a),(T()),()))>{}
+
+auto main() -> int                                   {
+  static_assert(!(std::invocable<decltype([]<typename T>(T const& x) -> std::void_t<decltype(f<T>())>{}),B>));
+}
+

regression-tests/test-results/pure2-bugfix-for-ufcs-sfinae.cpp2.output

@@ -0,0 +1,2 @@
+pure2-bugfix-for-ufcs-sfinae.cpp2... ok (all Cpp2, passes safety checks)
+

source/cppfront.cpp

@@ -1004,6 +1004,8 @@ class cppfront
     bool violates_initialization_safety = false;
     bool suppress_move_from_last_use    = false;
 
+    declaration_node const* having_signature_emitted = {};
+
     declaration_node const*   generating_assignment_from  = {};
     declaration_node const*   generating_move_from        = {};
     bool                      emitting_that_function      = false;
@@ -2946,7 +2948,13 @@ class cppfront
                 if (
                     current_declarations.back()->is_namespace()
                     || (
-                        current_declarations.back()->is_object()
+                        (
+                         current_declarations.back()->is_object()
+                         || (
+                             current_declarations.back()->is_function()
+                             && current_declarations.back() == having_signature_emitted
+                             )
+                         )
                         && current_declarations.back()->parent_is_namespace()
                         )
                     )
@@ -4829,6 +4837,13 @@ class cppfront
             printer.print_extra("\n");
         }
 
+        auto stack_value = []<typename T>(T& var, std::type_identity_t<T> const& value) {
+            return finally([&var, old = std::exchange(var, value)]() {
+                var = old;
+            });
+        };
+        auto stack = stack_value(having_signature_emitted, &n);
+
         //  Handle aliases
 
         if (n.is_alias())
@@ -5613,7 +5628,8 @@ class cppfront
                     function_returns.emplace_back(nullptr);        // no return type at all
                 }
 
-                for (auto&& c : func->contracts)
+                for (auto stack = stack_value(having_signature_emitted, nullptr);
+                     auto&& c : func->contracts)
                 {
                     auto print = std::string();
                     printer.emit_to_string(&print);
@@ -5680,6 +5696,7 @@ class cppfront
 
                 emit_requires_clause();
 
+                having_signature_emitted = nullptr;
                 emit(
                     *n.initializer,
                     true, func->position(), func->returns.index() == function_type_node::empty,