diff options
Diffstat (limited to '')
| -rw-r--r-- | src/doc/reference/src/items/type-aliases.md | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/src/doc/reference/src/items/type-aliases.md b/src/doc/reference/src/items/type-aliases.md index ff0cc75f7..d2e14b903 100644 --- a/src/doc/reference/src/items/type-aliases.md +++ b/src/doc/reference/src/items/type-aliases.md @@ -4,7 +4,7 @@ > _TypeAlias_ :\ > `type` [IDENTIFIER] [_GenericParams_]<sup>?</sup> > ( `:` [_TypeParamBounds_] )<sup>?</sup> -> [_WhereClause_]<sup>?</sup> ( `=` [_Type_] )<sup>?</sup> `;` +> [_WhereClause_]<sup>?</sup> ( `=` [_Type_] [_WhereClause_]<sup>?</sup>)<sup>?</sup> `;` A _type alias_ defines a new name for an existing [type]. Type aliases are declared with the keyword `type`. Every value has a single, specific type, but @@ -31,11 +31,18 @@ let _ = UseAlias(5); // OK let _ = TypeAlias(5); // Doesn't work ``` -A type alias without the [_Type_] specification may only appear as an -[associated type] in a [trait]. +A type alias, when not used as an associated type, must include a [_Type_] and +may not include [_TypeParamBounds_]. -A type alias with [_TypeParamBounds_] may only specified when used as -an [associated type] in a [trait]. +A type alias, when used as an [associated type] in a [trait], must not include a +[_Type_] specification but may include [_TypeParamBounds_]. + +A type alias, when used as an [associated type] in a [trait impl], must include +a [_Type_] specification and may not include [_TypeParamBounds_]. + +Where clauses before the equals sign on a type alias in a [trait impl] (like +`type TypeAlias<T> where T: Foo = Bar<T>`) are deprecated. Where clauses after +the equals sign (like `type TypeAlias<T> = Bar<T> where T: Foo`) are preferred. [IDENTIFIER]: ../identifiers.md [_GenericParams_]: generics.md @@ -45,3 +52,4 @@ an [associated type] in a [trait]. [associated type]: associated-items.md#associated-types [trait]: traits.md [type]: ../types.md +[trait impl]: implementations.md#trait-implementations |