Remove incorrect coercion. Define type coercions. #342
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| @@ -53,7 +53,7 @@ sites are: | |||
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| ``` | |||
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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?
| @@ -91,7 +91,7 @@ the block has a known type. | |||
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| Coercion is allowed between the following types: | |||
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| * `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
| @@ -164,8 +164,7 @@ the compiler will provide an implementation of `Unsize<U>` for `T`: | |||
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| * `[T; n]` to `[T]`. | |||
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| * `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?
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@Havvy Can you make the changes for this one? |
| @@ -1,10 +1,10 @@ | |||
| # Type coercions | |||
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| 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.
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