pub struct Instance<'tcx> {
    pub def: InstanceDef<'tcx>,
    pub substs: SubstsRef<'tcx>,
Expand description

A monomorphized InstanceDef.

Monomorphization happens on-the-fly and no monomorphized MIR is ever created. Instead, this type simply couples a potentially generic InstanceDef with some substs, and codegen and const eval will do all required substitution as they run.


§def: InstanceDef<'tcx>§substs: SubstsRef<'tcx>


Returns the Ty corresponding to this Instance, with generic substitutions applied and lifetimes erased, allowing a ParamEnv to be specified for use during normalization.

Finds a crate that contains a monomorphization of this instance that can be linked to from the local crate. A return value of None means no upstream crate provides such an exported monomorphization.

This method already takes into account the global -Zshare-generics setting, always returning None if share-generics is off.

Resolves a (def_id, substs) pair to an (optional) instance – most commonly, this is used to find the precise code that will run for a trait method invocation, if known.

Returns Ok(None) if we cannot resolve Instance to a specific instance. For example, in a context like this,

fn foo<T: Debug>(t: T) { ... }

trying to resolve Debug::fmt applied to T will yield Ok(None), because we do not know what code ought to run. (Note that this setting is also affected by the RevealMode in the parameter environment.)

Presuming that coherence and type-check have succeeded, if this method is invoked in a monomorphic context (i.e., like during codegen), then it is guaranteed to return Ok(Some(instance)).

Returns Err(ErrorGuaranteed) when the Instance resolution process couldn’t complete due to errors elsewhere - this is distinct from Ok(None) to avoid misleading diagnostics when an error has already been/will be emitted, for the original cause

Depending on the kind of InstanceDef, the MIR body associated with an instance is expressed in terms of the generic parameters of self.def_id(), and in other cases the MIR body is expressed in terms of the types found in the substitution array. In the former case, we want to substitute those generic types and replace them with the values from the substs when monomorphizing the function body. But in the latter case, we don’t want to do that substitution, since it has already been done effectively.

This function returns Some(substs) in the former case and None otherwise – i.e., if this function returns None, then the MIR body does not require substitution during codegen.

Returns a new Instance where generic parameters in instance.substs are replaced by identity parameters if they are determined to be unused in instance.def.

Trait Implementations§

Returns a copy of the value. Read more
Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
Formats the value using the given formatter. Read more
Feeds this value into the given Hasher. Read more
Feeds a slice of this type into the given Hasher. Read more
Given an instance of this key, what crate is it referring to? This is used to find the provider. Read more
In the event that a cycle occurs, if no explicit span has been given for a query with key self, what span should we use? Read more
If the key is a DefId or DefId–equivalent, return that DefId. Otherwise, return None. Read more
This method tests for self and other values to be equal, and is used by ==. Read more
This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason. Read more
The entry point for folding. To fold a value t with a folder f call: t.try_fold_with(f). Read more
A convenient alternative to try_fold_with for use with infallible folders. Do not override this method, to ensure coherence with try_fold_with. Read more
The entry point for visiting. To visit a value t with a visitor v call: t.visit_with(v). Read more
Returns true if self has any late-bound regions that are either bound by binder or bound by some binder outside of binder. If binder is ty::INNERMOST, this indicates whether there are any late-bound regions that appear free. Read more
Returns true if this self has any regions that escape binder (and hence are not bound by it). Read more
“Free” regions in this context means that it has any region that is not (a) erased or (b) late-bound. Read more
True if there are any un-erased free regions.
Indicates whether this value references only ‘global’ generic parameters that are the same regardless of what fn we are in. This is used for caching. Read more
True if there are any late-bound regions
Indicates whether this value still has parameters/placeholders/inference variables which could be replaced later, in a way that would change the results of impl specialization. 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
This method turns the parameters of a DepNodeConstructor into an opaque Fingerprint to be used in DepNode. Not all DepNodeParams support being turned into a Fingerprint (they don’t need to if the corresponding DepNode is anonymous). Read more
This method tries to recover the query key from the given DepNode, something which is needed when forcing DepNodes during red-green evaluation. The query system will only call this method if fingerprint_style() is not FingerprintStyle::Opaque. It is always valid to return None here, in which case incremental compilation will treat the query as having changed instead of forcing it. 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 resulting type after obtaining ownership.
Creates owned data from borrowed data, usually by cloning. Read more
Uses borrowed data to replace owned data, usually by cloning. Read more
Converts the given value to a String. Read more
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.


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: 32 bytes