Using Kernel.match?/2 to check if variable contains anonymous function AST increases size by 5 in Credo.Check.Refactor.ABCSize

[Eiji7]

Environment

• Credo version (mix credo -v):

$ mix credo -v
1.7.10-ref.main.1d74cf6+uncommittedchanges

• Erlang/Elixir version (elixir -v):

$ elixir -v
Erlang/OTP 27 [erts-15.1] [source] [64-bit] [smp:32:32] [ds:32:32:10] [async-threads:1] [jit:ns]

Elixir 1.17.3 (compiled with Erlang/OTP 27)

• Operating system:

Gentoo Linux using desktop/plasma profile for version 23.0 and with kernel version 6.6.41.

What were you trying to do?

Replaced if condition by true for debug ABCSize check

if match?({:fn, _meta, _args}, ast) do
  # …
end

Expected outcome

No idea how much points are expected, but 5 is definitely too much as just 6 lines with such a simple match? call would reach a limit.

The ABC size describes a metric based on assignments, branches and conditions.

1. Since ast is assigned above if condition I guess it should not count, right?
2. Branches are dot calls (like: mod.fun(…), right? Maybe it counts as +1 because of AST expansion to Kernel.match?(…) form …
3. Kernel.match?/2 is not a condition (if, unless, for, try, case, cond, and, or, &&, ||)

If that's correct then it should count as +1 for size. Not sure from where 5 comes - it does not match even if we count skipped patterns (_some_name) and ast with match? call would give at most 4 points. If you agree it would be awesome to count is as just +1 size, but as above I may be wrong here …

Actual outcome

Such a change decreases size by 5:

# after
if true do
  # …
end