Evan Mesterhazy 965d6ce4e4 Implement a procedural macro to derive the ContentHash trait for structs ... This is a no-op in terms of function, but provides a nicer way to derive the ContentHash trait for structs using the `#[derive(ContentHash)]` syntax used for other traits such as `Debug`. This commit only adds the macro. A subsequent commit will replace uses of `content_hash!{}` with `#[derive(ContentHash)]`. The new macro generates nice error messages, just like the old macro: ``` error[E0277]: the trait bound `NotImplemented: content_hash::ContentHash` is not satisfied --> lib/src/content_hash.rs:265:16 | 265 | z: NotImplemented, | ^^^^^^^^^^^^^^ the trait `content_hash::ContentHash` is not implemented for `NotImplemented` | = help: the following other types implement trait `content_hash::ContentHash`: bool i32 i64 u8 u32 u64 std::collections::HashMap<K, V> BTreeMap<K, V> and 38 others ``` This commit does two things to make proc macros re-exported by jj_lib useable by deps: 1. jj_lib needs to be able refer to itself as `jj_lib` which it does by adding an `extern crate self as jj_lib` declaration. 2. jj_lib::content_hash needs to re-export the `digest::Update` type so that users of jj_lib can use the `#[derive(ContentHash)]` proc macro without directly depending on the digest crate. This is done by re-exporting it as `DigestUpdate`. #3054		2024-02-20 11:29:05 -05:00
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src	Implement a procedural macro to derive the ContentHash trait for structs	2024-02-20 11:29:05 -05:00
Cargo.toml	Implement a procedural macro to derive the ContentHash trait for structs	2024-02-20 11:29:05 -05:00