This refactors much of the ast generation required for `deriving` instances into a common interface, so that new instances only need to specify what they do with the actual data, rather than worry about naming function arguments and extracting fields from structs and enum. (This all happens in `generic.rs`. I've tried to make sure it was well commented and explained, since it's a little abstract at points, but I'm sure it's still a little confusing.)
It makes instances like the comparison traits and `Clone` short and easy to write.
Caveats:
- Not surprisingly, this slows the expansion pass (in some cases, dramatically, specifically deriving Ord or TotalOrd on enums with many variants). However, this shouldn't be too concerning, since in a more realistic case (compiling `core.rc`) the time increased by 0.01s, which isn't worth mentioning. And, it possibly slows type checking very slightly (about 2% worst case), but I'm having trouble measuring it (and I don't understand why this would happen). I think this could be resolved by using traits and encoding it all in the type system so that monomorphisation handles everything, but that would probably be a little tricky to arrange nicely, reduce flexibility and make compiling rustc take longer. (Maybe some judicious use of `#[inline(always)]` would help too; I'll have a bit of a play with it.)
- The abstraction is not currently powerful enough for:
- `IterBytes`: doesn't support arguments of type other than `&Self`.
- `Encodable`/`Decodable` (#5090): doesn't support traits with parameters.
- `Rand` & `FromStr`; doesn't support static functions and arguments of type other than `&Self`.
- `ToStr`: I don't think it supports returning `~str` yet, but I haven't actually tried.
(The last 3 are traits that might be nice to have: the derived `ToStr`/`FromStr` could just read/write the same format as `fmt!("%?", x)`, like `Show` and `Read` in Haskell.)
I have ideas to resolve all of these, but I feel like it would essentially be a simpler version of the `mt` & `ty_` parts of `ast.rs`, and I'm not sure if the simplification is worth having 2 copies of similar code.
Also, makes Ord, TotalOrd and TotalEq derivable (closes#4269, #5588 and #5589), although a snapshot is required before they can be used in the rust repo.
If there is anything that is unclear (or incorrect) either here or in the code, I'd like to get it pointed out now, so I can explain/fix it while I'm still intimately familiar with the code.
This implements #5158. Currently it takes the command line args and the crate map. Since it doesn't take a `main` function pointer, you can't actually start the runtime easily, but that seems to be a shim to allow the current `rust_start` function to call into main.
However, you can do an end-run round the io library and do this:
```rust
use core::libc::{write, c_int, c_void, size_t, STDOUT_FILENO};
#[start]
fn my_start(_argc:int, _argv: **u8, _crate_map: *u8) -> int {
do str::as_buf("Hello World!\n") |s,len| {
unsafe {
write(STDOUT_FILENO, s as *c_void, len as size_t);
}
}
return 0;
}
```
Which is the most basic "Hello World" you can do in rust without starting up the runtime (though that has quite a lot to do with the fact that `core::io` uses `@` everywhere...)
Allow a deriving instance using the generic code to short-circuit for
any non-matching enum variants (grouping them all into a _ match),
reducing the number of arms required. Use this to speed up the Eq &
TotalEq implementations.
Pulls out many of the common patterns from the Eq and Clone deriving code (and
invents a few of its own), so that deriving instances are very easy to write
for a certain class of traits. (Basically, those which don't have parameters
and where all methods only take arguments of type `&Self` and return either
`Self` or types with no parameters.)
The code samples are xfail'ed because the buildbot won't have `libsnappy.so` and I don't want to add boilerplate to all the snippets (but they're directly from my snappy bindings so I'll just send a pull request whenever they break). It works really well as an example because it's tiny library and lets the caller manage all the buffers.
I think everything stated in the `Interoperability with foreign code` section is accurate but it deserves a thorough double-check :).
The example with OpenSSL is incorrect, because OpenSSL is using a
static variable for the return value and isn't thread-safe.
The gettimeofday example isn't great because it's not very portable.
This adds an example for most of the methods in Rng.
As a total newcomer to Rust, it took a while to figure out how to do basic things like use library functions, because there aren't many usage examples, and most examples that Google turns up are out of date. Something like this would have saved me a bit of time.
This might be a bit verbose. Some alternative options would be to consolidate all the examples into one section, or to only have code for the specific function call inline.
Good morning,
This first patch series adds support for `#[deriving(Decodable, Encodable)]`, but does not yet remove `#[auto_encode]` and `#[auto_decode]`. I need a snapshot to remove the old code. Along the way it also extends support for tuple structs and struct enum variants.
Also, it includes a minor fix to the pretty printer. We decided a while ago to use 4 spaces to indent a match arm instead of 2. This updates the pretty printer to reflect that.
