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@ -2,8 +2,8 @@
> Chalk is under heavy development, so if any of these links are broken or if > Chalk is under heavy development, so if any of these links are broken or if
> any of the information is inconsistent with the code or outdated, please > any of the information is inconsistent with the code or outdated, please
> [open an issue][rustc-issues] so we can fix it. If you are able to fix the issue yourself, we would > [open an issue][rustc-issues] so we can fix it. If you are able to fix the
> love your contribution! > issue yourself, we would love your contribution!
[Chalk][chalk] recasts Rust's trait system explicitly in terms of logic [Chalk][chalk] recasts Rust's trait system explicitly in terms of logic
programming by "lowering" Rust code into a kind of logic program we can then programming by "lowering" Rust code into a kind of logic program we can then
@ -42,7 +42,7 @@ Rust-like syntax.
The parser takes that syntax and produces an [Abstract Syntax Tree (AST)][ast]. The parser takes that syntax and produces an [Abstract Syntax Tree (AST)][ast].
You can find the [complete definition of the AST][chalk-ast] in the source code. You can find the [complete definition of the AST][chalk-ast] in the source code.
The syntax contains things from Rust that we know and love for example traits, The syntax contains things from Rust that we know and love, for example: traits,
impls, and struct definitions. Parsing is often the first "phase" of impls, and struct definitions. Parsing is often the first "phase" of
transformation that a program goes through in order to become a format that transformation that a program goes through in order to become a format that
chalk can understand. chalk can understand.
@ -67,14 +67,14 @@ essentially one of the following:
* `forall<T> { ... }` is represented in the code using the [`Binders<T>` * `forall<T> { ... }` is represented in the code using the [`Binders<T>`
struct][binders-struct]. struct][binders-struct].
This is the phase where we encode the rules of the trait system into logic. For Lowering is the phase where we encode the rules of the trait system into logic.
example, if we have: For example, if we have the following Rust:
```rust,ignore ```rust,ignore
impl<T: Clone> Clone for Vec<T> {} impl<T: Clone> Clone for Vec<T> {}
``` ```
We generate: We generate the following program clause:
```rust,ignore ```rust,ignore
forall<T> { (Vec<T>: Clone) :- (T: Clone) } forall<T> { (Vec<T>: Clone) :- (T: Clone) }
@ -102,22 +102,23 @@ For example, if you have a type like `Foo<Bar>`, we would represent `Foo` as a
string in the AST but in `ir::Program`, we use numeric indices (`ItemId`). string in the AST but in `ir::Program`, we use numeric indices (`ItemId`).
In addition to `ir::Program` which has "rust-like things", there is also In addition to `ir::Program` which has "rust-like things", there is also
`ir::ProgramEnvironment` which is "pure logic". The main field in that is `ir::ProgramEnvironment` which is "pure logic". The main field in that struct is
`program_clauses` which contains the `ProgramClause`s that we generated `program_clauses` which contains the `ProgramClause`s that we generated
previously. previously.
## Rules ## Rules
The `rules` module works by iterating over every trait, impl, etc. and emitting The `rules` module works by iterating over every trait, impl, etc. and emitting
the rules that come from each one. The traits section of the rustc-guide (that the rules that come from each one. See [Lowering Rules][lowering-rules] for the
you are currently reading) contains the most up-to-date reference on that. most up-to-date reference on that.
The `ir::ProgramEnvironment` is created [in this module][rules-environment]. The `ir::ProgramEnvironment` is created [in this module][rules-environment].
## Testing ## Testing
TODO: Basically, [there is a macro](https://github.com/rust-lang-nursery/chalk/blob/94a1941a021842a5fcb35cd043145c8faae59f08/src/solve/test.rs#L112-L148) TODO: Basically, [there is a macro](https://github.com/rust-lang-nursery/chalk/blob/94a1941a021842a5fcb35cd043145c8faae59f08/src/solve/test.rs#L112-L148)
that will take syntax and run it through the full pipeline described above. that will take chalk's Rust-like syntax and run it through the full pipeline
described above.
[This](https://github.com/rust-lang-nursery/chalk/blob/94a1941a021842a5fcb35cd043145c8faae59f08/src/solve/test.rs#L83-L110) [This](https://github.com/rust-lang-nursery/chalk/blob/94a1941a021842a5fcb35cd043145c8faae59f08/src/solve/test.rs#L83-L110)
is the function that is ultimately called. is the function that is ultimately called.