import 15.2.0 Octopus source

[ceph.git] / ceph / src / seastar / coding-style.md

diff --git a/ceph/src/seastar/coding-style.md b/ceph/src/seastar/coding-style.md
index d278fc1cf0df6dff45668ad5a9d599cc747bf3d4..c5bfe2ccae76923a637fa54eac48be29ebd257e1 100644 (file)
--- a/ceph/src/seastar/coding-style.md
+++ b/ceph/src/seastar/coding-style.md
@@ -133,3 +133,18 @@ If a line becomes excessively long (>120 characters?), or is just complicated, b
 
 Of course, long lines or complex conditions may indicate that refactoring is in order.
 
+## Generic lambdas and types
+
+Generic lambdas (`[] (auto param)`) are discouraged where the type is known. Generic
+lambdas reduce the compiler's and other tools' ability to reason about the code.
+In case the actual type of `param` doesn't match the programmers expectations,
+the compiler will only detect an error in the lambda body, or perhaps
+even lower down the stack if more generic functions are called. In the case of an
+IDE, most of its functionality is disabled in a generic lambda, since it can't
+assume anything about that parameter.
+
+Of course, when there is a need to support multiple types, genericity is the correct
+tool. Even then, type parameters should be constrained with concepts, in order to
+catch type mismatches early rather than deep in the instantiation chain.
+
+