# Enum chalk_solve::solve::Solution

``````pub enum Solution<I: Interner> {
Unique(Canonical<ConstrainedSubst<I>>),
Ambig(Guidance<I>),
}``````
Expand description

A (possible) solution for a proposed goal.

## Variants§

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### Unique(Canonical<ConstrainedSubst<I>>)

The goal indeed holds, and there is a unique value for all existential variables. In this case, we also record a set of lifetime constraints which must also hold for the goal to be valid.

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### Ambig(Guidance<I>)

The goal may be provable in multiple ways, but regardless we may have some guidance for type inference. In this case, we don’t return any lifetime constraints, since we have not “committed” to any particular solution yet.

## Implementations§

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### impl<I: Interner> Solution<I>

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#### pub fn combine(self, other: Solution<I>, interner: I) -> Solution<I>

There are multiple candidate solutions, which may or may not agree on the values for existential variables; attempt to combine them. This operation does not depend on the order of its arguments.

This actually isn’t as precise as it could be, in two ways:

a. It might be that while there are multiple distinct candidates, they all agree about some things. To be maximally precise, we would compute the intersection of what they agree on. It’s not clear though that this is actually what we want Rust’s inference to do, and it’s certainly not what it does today.

b. There might also be an ambiguous candidate and a successful candidate, both with the same refined-goal. In that case, we could probably claim success, since if the conditions of the ambiguous candidate were met, we know the success would apply. Example: `?0: Clone` yields ambiguous candidate `Option<?0>: Clone` and successful candidate `Option<?0>: Clone`.

But you get the idea.

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#### pub fn into_guidance(self) -> Guidance<I>

View this solution purely in terms of type inference guidance

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#### pub fn constrained_subst( &self, interner: I ) -> Option<Canonical<ConstrainedSubst<I>>>

Extract a constrained substitution from this solution, even if ambiguous.

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#### pub fn definite_subst( &self, interner: I ) -> Option<Canonical<ConstrainedSubst<I>>>

Determine whether this solution contains type information that must hold, and returns the subst in that case.

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## Trait Implementations§

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### impl<I: Clone + Interner> Clone for Solution<I>

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#### fn clone(&self) -> Solution<I>

Returns a copy of the value. Read more
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#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
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### impl<I: Debug + Interner> Debug for Solution<I>

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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### impl<I: Interner> HasInterner for Solution<I>

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#### type Interner = I

The interner associated with the type.
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### impl<I: PartialEq + Interner> PartialEq for Solution<I>

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#### fn eq(&self, other: &Solution<I>) -> bool

This method tests for `self` and `other` values to be equal, and is used by `==`.
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#### fn ne(&self, other: &Rhs) -> bool

This method tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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## Blanket Implementations§

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### impl<T> Any for Twhere T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for Twhere T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for Twhere T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> Cast for T

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#### fn cast<U>(self, interner: <U as HasInterner>::Interner) -> Uwhere Self: CastTo<U>, U: HasInterner,

Cast a value to type `U` using `CastTo`.
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### impl<Q, K> Equivalent<K> for Qwhere Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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#### fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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### impl<Q, K> Equivalent<K> for Qwhere Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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#### fn equivalent(&self, key: &K) -> bool

Compare self to `key` and return `true` if they are equal.
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T> Instrument for T

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#### fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided [`Span`], returning an `Instrumented` wrapper. Read more
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#### fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current `Span`, returning an `Instrumented` wrapper. Read more
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### impl<T, U> Into<U> for Twhere U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

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

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### impl<T> ToOwned for Twhere T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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### impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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### impl<T> WithSubscriber for T

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#### fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>where S: Into<Dispatch>,

Attaches the provided `Subscriber` to this type, returning a [`WithDispatch`] wrapper. Read more
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#### fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default `Subscriber` to this type, returning a [`WithDispatch`] wrapper. Read more