Enum rustc_trait_selection::infer::canonical::CanonicalTyVarKind

pub enum CanonicalTyVarKind {
    General(UniverseIndex),
    Int,
    Float,
}

Rust actually has more than one category of type variables; notably, the type variables we create for literals (e.g., 22 or 22.) can only be instantiated with integral/float types (e.g., usize or f32). In order to faithfully reproduce a type, we need to know what set of types a given type variable can be unified with.

Variants

General(UniverseIndex)

General type variable ?T that can be unified with arbitrary types.

Int

Integral type variable ?I (that can only be unified with integral types).

Float

Floating-point type variable ?F (that can only be unified with float types).