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Clarify language in Trait Resolution

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Tyler Mandry 2018-05-11 21:06:21 -05:00 committed by Who? Me?!
parent d491bce01d
commit 3ea4a0b683
1 changed files with 3 additions and 3 deletions
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6
src/trait-resolution.md
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@ -202,8 +202,8 @@ impl<T:Get> Get for Box<T> {
What happens when we invoke `get_it(&Box::new(1_u16))`, for example? In this What happens when we invoke `get_it(&Box::new(1_u16))`, for example? In this
case, the `Self` type is `Box<u16>` – that unifies with both impls, case, the `Self` type is `Box<u16>` – that unifies with both impls,
because the first applies to all types, and the second to all because the first applies to all types `T`, and the second to all
boxes. In order for this to be unambiguous, the compiler does a *winnowing* `Box<T>`. In order for this to be unambiguous, the compiler does a *winnowing*
pass that considers `where` clauses pass that considers `where` clauses
and attempts to remove candidates. In this case, the first impl only and attempts to remove candidates. In this case, the first impl only
applies if `Box<u16> : Copy`, which doesn't hold. After winnowing, applies if `Box<u16> : Copy`, which doesn't hold. After winnowing,
@ -242,7 +242,7 @@ fn foo<X:A2+B>(x: X) {
In the body of `foo`, clearly we can use methods of `A1`, `A2`, or `B` In the body of `foo`, clearly we can use methods of `A1`, `A2`, or `B`
on variable `x`. The line marked `(*)` will incur an obligation `X: A1`, on variable `x`. The line marked `(*)` will incur an obligation `X: A1`,
which the line marked `(#)` will incur an obligation `X: B`. Meanwhile, while the line marked `(#)` will incur an obligation `X: B`. Meanwhile,
the parameter environment will contain two where-clauses: `X : A2` and `X : B`. the parameter environment will contain two where-clauses: `X : A2` and `X : B`.
For each obligation, then, we search this list of where-clauses. The For each obligation, then, we search this list of where-clauses. The
obligation `X: B` trivially matches against the where-clause `X: B`. obligation `X: B` trivially matches against the where-clause `X: B`.