Cargo Features
extern-existential has no features set by default.
[dependencies]
extern-existential = { version = "0.1.2", features = ["rustc-dep-of-std"] }- rustc-dep-of-std = compiler_builtins, core
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.