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Remove incorrect coercion. Define type coercions. - #342
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| ``` | ||
| * Function results, either the final line of a block if it is not | ||
| * Function results – either the final line of a block if it is not |
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Style nitpick: shouldn't this be an em dash without surrounding spaces?
| Coercion is allowed between the following types: | ||
| * `T` to `U` if `T` is a subtype of `U` (*reflexive case*) | ||
| * `T` to `U` if `T` is a [subtype] of `U` (*reflexive case*) |
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Does the "reflexive case" annotation mean anything here? T to U when they are distinct is not reflexivity, although this does imply reflexivity because T is a subtype of T
| * `T` to `U`, when `U` is a trait object type and either `T` implements `U` or | ||
| `T` is a trait object for a subtrait of `U`. | ||
| * `T` to `dyn U`, when `T` implements `U + Sized` |
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I don't think + Sized is accurate here; without it, coercions of references won't always work because going from &T to &U would require that T be sized. Unless that's actually how it works?
alercah
commented
Aug 3, 2018
@Havvy Can you make the changes for this one? |
| Coercions are defined in [RFC 401]. [RFC 1558] then expanded on that. | ||
| A coercion is implicit and has no syntax. | ||
| **Type coercions** are implicit changes of the type of a value. They happen |
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Nitpick: An implicit coercion is essentially an implicit operation on a value. The value doesn't so much change type as there's an invisible "function call" on the value that produces a different value (this gets muddied a bit by subtyping and ownership). The language Idris allows one to define implicit functions and one can think of the implicit coercions in Rust as a set of those.
Havvy
commented
Nov 5, 2020
This is outdated. |
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