forked from mirrors/jj
965d6ce4e4
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
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265 | z: NotImplemented,
| ^^^^^^^^^^^^^^ the trait `content_hash::ContentHash` is not implemented for `NotImplemented`
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= 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
16 lines
280 B
TOML
16 lines
280 B
TOML
[package]
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name = "jj-lib-proc-macros"
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publish = false
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version = { workspace = true }
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edition = { workspace = true }
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license = { workspace = true }
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[lib]
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proc-macro = true
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[dependencies]
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proc-macro2 = { workspace = true }
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quote = { workspace = true }
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syn = { workspace = true }
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