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DST custom coercions. #982

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merged 5 commits into from
Jun 3, 2015
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DST custom coercions. #982

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bf8d81b
DST custom coercions.
nrc Mar 16, 2015
4d803c1
Tweak newtype coercions, remove ?Sized requirement.
nrc Mar 16, 2015
97452ca
Remove newtype coercions, make CoerceUnsized coercions more general
nrc Mar 18, 2015
7468c30
Address some comments
nrc Mar 24, 2015
4b99006
eddyb's changes
nrc Jun 3, 2015
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Tweak newtype coercions, remove ?Sized requirement.
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@nrc
nrc committed Jun 3, 2015
commit 4d803c14371ca7cbfd327b3db9735ed3ba58e31f
7 changes: 3 additions & 4 deletions text/0000-dst-coercion.md
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Expand Up @@ -66,9 66,8 @@ coerced to the `Target` type. E.g., the above implementation means that
## Newtype coercions

We also add a new built-in coercion for 'newtype's. If `Foo<T>` is a tuple
struct with a single field with type `T` and `T` has at least the `?Sized`
bound, then coerce_inner(`Foo<T>`) = `Foo<U>` holds for any `T` and `U` where
`T` coerces to `U`.
struct with a single field with type `T`, then coerce_inner(`Foo<T>`) = `Foo<U>`
holds for any `T` and `U` where `T` coerces to `U`.

This coercion is not opt-in. It is best thought of as an extension to the
coercion rule for structs with an unsized field, the extension is that here the
Expand Down Expand Up @@ -121,7 120,7 @@ adjustment.
### Adjustment types

We add `AdjustCustom(usize, Box<AutoAdjustment>)` and
`AdjustNewtype(Box<AutoAdjustment>)` to the `AutoAdjustment` enum. These
`AdjustNewtype(Box<AutoDerefRef>)` to the `AutoAdjustment` enum. These
represent the new custom and newtype coercions, respectively. We add
`UnsizePlaceHolder(Ty, Ty)` to the `UnsizeKind` enum to represent a placeholder
adjustment due to an `Unsize` bound.
Expand Down