From a61c2fe50bbddf04164d713003ae9b1ce006b427 Mon Sep 17 00:00:00 2001
From: Johannes Kalmbach <johannes.kalmbach@gmail.com>
Date: Fri, 14 Feb 2025 08:58:45 +0100
Subject: [PATCH] Fix the lambdas

Signed-off-by: Johannes Kalmbach <johannes.kalmbach@gmail.com>
---
 src/backports/concepts.h     | 66 +++++++-----------------------------
 src/backports/cppTemplate2.h | 19 ++++++++++-
 2 files changed, 30 insertions(+), 55 deletions(-)

diff --git a/src/backports/concepts.h b/src/backports/concepts.h
index 98aee3c9e3..5873f7d0ea 100644
--- a/src/backports/concepts.h
+++ b/src/backports/concepts.h
@@ -19,11 +19,15 @@
 // resolution.
 //
 // `QL_CONCEPT_OR_TYPENAME(arg)`: expands to `arg` in C++20 mode, and to
-// `typename` in C++17 mode.
+// `typename` in C++17 mode. Example usage:
 //
 // `CPP_lambda(capture)(arg)(requires ...)`: Expands lambda to use
 //  `requires` in C++20 mode and `std::enable_if_t` in C++17 mode.
 //
+// `CPP_template_lambda(capture)(typenames...)(arg)(requires ...)`: Expands
+// lambda with (C++20) explicit gemplate parameters  to use
+//  `requires` in C++20 mode and `std::enable_if_t` in C++17 mode.
+//
 // Example usages:
 //
 // `QL_CONCEPT_OR_NOTHING(std::view) auto x = someFunction();`
@@ -37,6 +41,9 @@
 // `auto myLambda = CPP_lambda(someCapture)(someArg)(requires
 // ranges::same_as<decltype(someArg), int>) {...}`
 //
+// `auto myLambda2 = CPP_lambda(someCapture)(typename F)(F arg)(requires
+// ranges::same_as<F, int>) {...}`
+//
 // NOTE: The macros are variadic to allow for commas in the argument, like in
 // the second example above.
 
@@ -54,45 +61,9 @@
 #define CPP_and_2_def CPP_and_2_def_sfinae
 #define CPP_variadic_template CPP_template_NO_DEFAULT_SFINAE
 #define CPP_member_def CPP_member_def_sfinae
-
 #define CPP_lambda CPP_lambda_sfinae
-
+#define CPP_template_lambda CPP_template_lambda_sfinae
 #define CPP_lambda_mut CPP_lambda_mut_sfinae
-
-#define CPP_lambda_sfinae(...)     \
-  CPP_PP_IGNORE_CXX2A_COMPAT_BEGIN \
-  [__VA_ARGS__] CPP_LAMBDA_SFINAE_ARGS
-
-#define CPP_lambda_mut_sfinae(...) \
-  CPP_PP_IGNORE_CXX2A_COMPAT_BEGIN \
-  [__VA_ARGS__] CPP_LAMBDA_MUT_SFINAE_ARGS
-
-#define CPP_LAMBDA_SFINAE_ARGS(...) \
-    (__VA_ARGS__ CPP_LAMBDA_SFINAE_AUX_
-
-#define CPP_LAMBDA_MUT_SFINAE_ARGS(...) \
-    (__VA_ARGS__ CPP_LAMBDA_MUT_SFINAE_AUX_
-
-#define CPP_LAMBDA_SFINAE_AUX_WHICH_(FIRST, ...) \
-  CPP_PP_EVAL(CPP_PP_CHECK, FIRST)
-
-#define CPP_LAMBDA_SFINAE_AUX_(...)                       \
-  CPP_PP_CAT(CPP_LAMBDA_SFINAE_AUX_,                      \
-             CPP_LAMBDA_SFINAE_AUX_WHICH_(__VA_ARGS__, )) \
-  (__VA_ARGS__)
-
-#define CPP_LAMBDA_MUT_SFINAE_AUX_(...)                   \
-  CPP_PP_CAT(CPP_LAMBDA_SFINAE_AUX_,                      \
-             CPP_LAMBDA_SFINAE_AUX_WHICH_(__VA_ARGS__, )) \
-  (__VA_ARGS__) mutable
-
-#define CPP_LAMBDA_SFINAE_AUX_0(...) ,                           \
-    std::enable_if_t<                                            \
-        CPP_PP_CAT(CPP_LAMBDA_SFINAE_AUX_3_, __VA_ARGS__)        \
-        >* = nullptr)
-
-#define CPP_LAMBDA_SFINAE_AUX_3_requires
-
 #else
 #define QL_CONCEPT_OR_NOTHING(...) __VA_ARGS__
 #define QL_CONCEPT_OR_TYPENAME(...) __VA_ARGS__
@@ -102,22 +73,9 @@
 #define CPP_and_2_def CPP_and
 #define CPP_variadic_template CPP_template
 #define CPP_member_def CPP_member
-
-#define CPP_lambda(...) [__VA_ARGS__] CPP_LAMBDA_ARGS
-
-#define CPP_lambda_mut(...) [__VA_ARGS__] CPP_LAMBDA_ARGS_MUT
-
-#define CPP_LAMBDA_ARGS(...) (__VA_ARGS__) CPP_LAMBDA_AUX_
-
-#define CPP_LAMBDA_ARGS_MUT(...) (__VA_ARGS__) mutable CPP_LAMBDA_AUX_
-
-#define CPP_LAMBDA_AUX_(...) \
-  CPP_PP_CAT(CPP_LAMBDA_AUX_, CPP_LAMBDA_AUX_WHICH_(__VA_ARGS__, ))(__VA_ARGS__)
-
-#define CPP_LAMBDA_AUX_WHICH_(FIRST, ...) CPP_PP_EVAL(CPP_PP_CHECK, FIRST)
-
-#define CPP_LAMBDA_AUX_0(...) __VA_ARGS__
-
+#define CPP_lambda CPP_LAMBDA_20
+#define CPP_template_lambda CPP_TEMPLATE_LAMBDA_20
+#define CPP_lambda_mut CPP_lambda_mut_20
 #endif
 
 // The namespace `ql::concepts` includes concepts that are contained in the
diff --git a/src/backports/cppTemplate2.h b/src/backports/cppTemplate2.h
index 171dc5dca4..e250034f19 100644
--- a/src/backports/cppTemplate2.h
+++ b/src/backports/cppTemplate2.h
@@ -68,7 +68,9 @@
 (__VA_ARGS__ CPP_LAMBDA_SFINAE_AUX_
 
 #define CPP_LAMBDA_SFINAE_AUX_WHICH_(FIRST, ...) \
-  CPP_PP_EVAL(CPP_PP_CHECK, CPP_PP_CAT(CPP_LAMBDA_SFINAE_PROBE_CONCEPT_, FIRST))
+  CPP_PP_EVAL(CPP_PP_CHECK, FIRST)
+//  CPP_PP_EVAL(CPP_PP_CHECK, CPP_PP_CAT(CPP_LAMBDA_SFINAE_PROBE_CONCEPT_,
+//  FIRST))
 
 #define CPP_LAMBDA_SFINAE_AUX_(...)                       \
   CPP_PP_CAT(CPP_LAMBDA_SFINAE_AUX_,                      \
@@ -102,3 +104,18 @@ CPP_PP_CAT(CPP_LAMBDA_SFINAE_AUX_3_, __VA_ARGS__)        \
 #define CPP_LAMBDA_AUX_0(...) __VA_ARGS__
 
 #define CPP_TEMPLATE_LAMBDA_ARGS(...) <__VA_ARGS__> CPP_LAMBDA_ARGS
+
+#define CPP_lambda_mut_sfinae(...) \
+  CPP_PP_IGNORE_CXX2A_COMPAT_BEGIN \
+  [__VA_ARGS__] CPP_LAMBDA_MUT_SFINAE_ARGS
+
+#define CPP_LAMBDA_MUT_SFINAE_ARGS(...) \
+(__VA_ARGS__ CPP_LAMBDA_MUT_SFINAE_AUX_
+
+#define CPP_LAMBDA_MUT_SFINAE_AUX_(...)                   \
+  CPP_PP_CAT(CPP_LAMBDA_SFINAE_AUX_,                      \
+             CPP_LAMBDA_SFINAE_AUX_WHICH_(__VA_ARGS__, )) \
+  (__VA_ARGS__) mutable
+
+#define CPP_LAMBDA_ARGS_MUT(...) (__VA_ARGS__) mutable CPP_LAMBDA_AUX_
+#define CPP_lambda_mut_20(...) [__VA_ARGS__] CPP_LAMBDA_ARGS_MUT