feature_macros

This crate allows for controling how safe/unsafe other crates are.

Example

This macro can (but should not necessarily) be used identically to unreachable! or panic!.

```rust

match x {
    Foo::Bar => bar(&x),
    Foo::Baz => baz(&x),
    _ => inconceivable!(),
}

```

Developer Controllable Options

• ub_inconceivable: This controls the semantics of the inconceivable! macro. When this options is not supplied (or when this options is supplied, and the crate is compiled with rustc --version < 1.27) inconceivable! will simply alias unreachable!. When this option is supplied (and the crate is compiled with rustc --version >= 1.27) this will instead emit unreachable_uncheck() which is UB.

Developer Uncontrollable Options

• RUSTC_VERSION_GE_1_27: States if rustc --version >= 1.27 this is used as a feature check.