Cargo Features

LinkedHashMap has no features set by default.

linked-hash-map = { version = "0.5.6", features = ["nightly", "serde_impl", "heapsize_impl"] }
serde_impl = serde

Affects linked-hash-map::serde

heapsize_impl = heapsize

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.

serde serde_impl?
heapsize heapsize_impl?