Struct rustc_middle::ty::_match::Match

source ·
pub struct Match<'tcx> {
    tcx: TyCtxt<'tcx>,
    param_env: ParamEnv<'tcx>,
}
Expand description

A type “A” matches “B” if the fresh types in B could be substituted with values so as to make it equal to A. Matching is intended to be used only on freshened types, and it basically indicates if the non-freshened versions of A and B could have been unified.

It is only an approximation. If it yields false, unification would definitely fail, but a true result doesn’t mean unification would succeed. This is because we don’t track the “side-constraints” on type variables, nor do we track if the same freshened type appears more than once. To some extent these approximations could be fixed, given effort.

Like subtyping, matching is really a binary relation, so the only important thing about the result is Ok/Err. Also, matching never affects any type variables or unification state.

Fields§

§tcx: TyCtxt<'tcx>§param_env: ParamEnv<'tcx>

Implementations§

Trait Implementations§

Returns a static string we can use for printouts.
Returns true if the value a is the “expected” type in the relation. Just affects error messages. Read more
Used during coherence. If called, must emit an always-ambiguous obligation.
Switch variance for the purpose of relating a and b.
Generic relation routine suitable for most anything.
Relate the two substitutions for the given item. The default is to look up the variance for the item and proceed accordingly. Read more

Auto Trait Implementations§

Blanket Implementations§

Gets the TypeId of self. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.

Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference’s “Type Layout” chapter for details on type layout guarantees.

Size: 16 bytes