From 2fd4e604a46d1175f260a33efdfcacb7b48ed1ff Mon Sep 17 00:00:00 2001 From: Postmodern Date: Thu, 19 May 2016 17:07:29 -0700 Subject: [PATCH] Clarify the English translation of `?Sized` * It wasn't clear whether `?Sized` meant "not `Sized`" or "`Sized` or not `Sized`". According to #rust IRC, it does indeed mean "`Sized` or not `Sized`". * Use the same language as [Trait std::marker::Sized](https://doc.rust-lang.org/std/marker/trait.Sized.html) about how `Sized` is implicitly bound. --- src/doc/book/unsized-types.md | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/src/doc/book/unsized-types.md b/src/doc/book/unsized-types.md index 73b90355e4f1..d94409a7b827 100644 --- a/src/doc/book/unsized-types.md +++ b/src/doc/book/unsized-types.md @@ -47,7 +47,7 @@ pointers, can use this `impl`. # ?Sized If you want to write a function that accepts a dynamically sized type, you -can use the special bound, `?Sized`: +can use the special syntax, `?Sized`: ```rust struct Foo { @@ -55,6 +55,5 @@ struct Foo { } ``` -This `?`, read as “T may be `Sized`”, means that this bound is special: it -lets us match more kinds, not less. It’s almost like every `T` implicitly has -`T: Sized`, and the `?` undoes this default. +This `?Sized`, read as “T may or may not be `Sized`”, allowing us to match both constant size and unsized types. +All generic type parameters implicitly have the `Sized` bound, so `?Sized` can be used to opt-out of the implicit bound.