Cargo Features

[dependencies]
ident_case_conversions = { version = "1.0.0", default-features = false, features = ["syn"] }
default = syn

The syn feature is set by default whenever ident_case_conversions is added without default-features = false somewhere in the dependency tree.

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.

syn default