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lib/reach/smell/checks/nested_enum.ex
defmodule Reach.Smell.Checks.NestedEnum do
@moduledoc "Detects Enum.member? nested inside another Enum traversal of the same variable."
use Reach.Smell.Check
@outer_fns ~w(map filter reduce each any? all? find find_value flat_map reject count)a
defp findings(function) do
all_nodes = IR.all_nodes(function)
outer_calls =
for node <- all_nodes,
node.type == :call,
node.meta[:module] == Enum,
node.meta[:function] in @outer_fns,
node.source_span,
[%{type: :var, meta: %{name: var}} | _] <- [node.children] do
{var, node}
end
Enum.flat_map(outer_calls, fn {var, outer} ->
inner_calls =
outer
|> Helpers.callback_body()
|> Enum.filter(fn n ->
n.type == :call and n.meta[:module] == Enum and
n.meta[:function] == :member? and not is_nil(n.source_span) and
match?([%{type: :var, meta: %{name: ^var}} | _], n.children)
end)
Enum.map(inner_calls, fn inner ->
finding(
:suboptimal,
"Enum.member?/2 nested inside Enum.#{outer.meta[:function]} on `#{var}` is O(n²); precompute a MapSet",
inner
)
end)
end)
end
end