Cargo Features

file_type_enum has no features set by default.

[dependencies]
file_type_enum = { version = "2.0.1", features = ["mode-t-conversion"] }
mode-t-conversion = libc

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

libc mode-t-conversion?