Make ConnectionManager implement Sync automatically #2321
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By using `PhantomData<fn() -> T>` instead of `PhantomData<T>` for the type of the `_marker` field, this makes `ConnectionManager` implement `Sync` automatically, and means we can remove the `unsafe impl` of `Sync` for `ConnectionManager<T>`.
Mingun
reviewed
Mar 7, 2020
| @@ -31,11 +31,9 @@ use crate::sql_types::HasSqlType; | |||
| #[derive(Debug, Clone)] | |||
| pub struct ConnectionManager<T> { | |||
| database_url: String, | |||
| _marker: PhantomData<T>, | |||
| _marker: PhantomData<fn() -> T>, | |||
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I think, you should leave comment from PR description that explains, why not just PhantomData<T> is used
weiznich
requested changes
Mar 9, 2020
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Please explain why how change is equivalent (or at least equivalent sound) to the original code. Without this change T: 'static is enforced for the Sync bound. This bound is remove by changing the PhantomData type. See this playground for a toy example.
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By using
PhantomData<fn() -> T>instead ofPhantomData<T>for the type of the_markerfield, this makesConnectionManagerimplementSyncautomatically, and means we can remove theunsafe implofSyncforConnectionManager<T>.