Type Alias FxHashMap 

pub type FxHashMap<K, V> = HashMap<K, V, FxBuildHasher>;

Centralized compatibility shims for compiler API differences across nightly versions.

When a type or function moves between modules or changes interface across rustc versions, add a re-export here (gated by #[cfg]). All other modules import from this crate instead of writing their own #[cfg] blocks.

How to add a new compat item

1. Add a cfg flag in build.rs (e.g. rustc_foo_moved).
2. Register it with emit_check_cfg in build.rs.
3. Add the re-export below.
4. Update call-sites to use crate::compat::Foo;. Type alias for a hash map that uses the Fx hashing algorithm.

Aliased Type

pub struct FxHashMap<K, V> { /* private fields */ }