From e0538ca63bf3b9ebb45baf1bd3e7ed2af8926f6b Mon Sep 17 00:00:00 2001
From: =?utf8?q?Rados=C5=82aw=20Zarzy=C5=84ski?= <rzarzyns@redhat.com>
Date: Wed, 26 Jul 2023 12:42:45 +0200
Subject: [PATCH] crimson/ertr: assert on invocability of func provided to
 safe_then()
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The goal is to fail with an easier-to-understand error on failed
`static_assert()` than cryptic template substitution errors when
the function provided to e.g. `safe_then()` doesn't match the type
carried within an errorated future.

Signed-off-by: Radosław Zarzyński <rzarzyns@redhat.com>
(cherry picked from commit 83687f2cc86897d60a460575a7ab2acbd2f9170c)
---
 src/crimson/common/errorator.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/crimson/common/errorator.h b/src/crimson/common/errorator.h
index 705a9f05210ce..c5d63d5b9c1d5 100644
--- a/src/crimson/common/errorator.h
+++ b/src/crimson/common/errorator.h
@@ -599,7 +599,9 @@ private:
       static_assert((... && std::is_invocable_v<ErrorVisitorT,
                                                 AllowedErrors>),
                     "provided Error Visitor is not exhaustive");
-
+      static_assert(std::is_void_v<ValueT> ? std::is_invocable_v<ValueFuncT>
+		                           : std::is_invocable_v<ValueFuncT, ValueT>,
+                    "Value Func is not invocable with future's value");
       using value_func_result_t =
         typename std::conditional_t<std::is_void_v<ValueT>,
 				    std::invoke_result<ValueFuncT>,
-- 
2.47.3