UnifyValue in rustc_data_structures::unify - Rust
Description: Trait implemented for values associated with a unification key. This trait defines how to merge the values from two keys that are unioned together. This merging can be fallible. If you attempt to union two keys whose values cannot be merged, then the error is propagated up and the two keys are not unioned.

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## UnifyValue

# Trait UnifyValue

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    pub trait UnifyValue: Clone + Debug {
        type Error;

        // Required method
        fn unify_values(value1: &Self, value2: &Self) -> Result<Self, Self::Error>;
    }

Expand description

Trait implemented for values associated with a unification key. This trait defines how to merge the values from two keys that are unioned together. This merging can be fallible. If you attempt to union two keys whose values cannot be merged, then the error is propagated up and the two keys are not unioned.

This crate provides implementations of `UnifyValue` for `()` (which is infallible) and `Option<T>` (where `T: UnifyValue`). The option implementation merges two sum-values using the `UnifyValue` implementation of `T`.

See also `EqUnifyValue`, which is a convenience trait for cases where the “merge” operation succeeds only if the two values are equal.

## Required Associated Types§

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#### type Error

Defines the type to return when merging of two values fails. If merging is infallible, use the special struct `NoError` found in this crate, which unlocks various more convenient methods on the unification table.

## Required Methods§

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#### fn unify_values(value1: &Self, value2: &Self) -> Result<Self, Self::Error>

Given two values, produce a new value that combines them. If that is not possible, produce an error.

## Dyn Compatibility§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

## Implementations on Foreign Types§

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### impl UnifyValue for ()

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#### type Error = NoError

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#### fn unify_values(_: &(), _: &()) -> Result<(), NoError>

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### impl<V> UnifyValue for Option<V>
where V: UnifyValue,

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#### type Error = <V as UnifyValue>::Error

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#### fn unify_values( a: &Option<V>, b: &Option<V>, ) -> Result<Option<V>, <V as UnifyValue>::Error>

## Implementors§

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### impl<T> UnifyValue for T
where T: EqUnifyValue,

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#### type Error = (T, T)