Implement constant support in MIR.
All of the intended features in `trans::consts` are now supported by `mir::constant`.
The implementation is considered a temporary measure until `miri` replaces it.
A `-Z orbit` bootstrap build will only translate LLVM IR from AST for `#[rustc_no_mir]` functions.
Furthermore, almost all checks of constant expressions have been moved to MIR.
In non-`const` functions, trees of temporaries are promoted, as per RFC 1414 (rvalue promotion).
Promotion before MIR borrowck would allow reasoning about promoted values' lifetimes.
The improved checking comes at the cost of four `[breaking-change]`s:
* repeat counts must contain a constant expression, e.g.:
`let arr = [0; { println!("foo"); 5 }];` used to be allowed (it behaved like `let arr = [0; 5];`)
* dereference of a reference to a `static` cannot be used in another `static`, e.g.:
`static X: [u8; 1] = [1]; static Y: u8 = (&X)[0];` was unintentionally allowed before
* the type of a `static` *must* be `Sync`, irrespective of the initializer, e.g.
`static FOO: *const T = &BAR;` worked as `&T` is `Sync`, but it shouldn't because `*const T` isn't
* a `static` cannot wrap `UnsafeCell` around a type that *may* need drop, e.g.
`static X: MakeSync<UnsafeCell<Option<String>>> = MakeSync(UnsafeCell::new(None));`
was previously allowed based on the fact `None` alone doesn't need drop, but in `UnsafeCell`
it can be later changed to `Some(String)` which *does* need dropping
The drop restrictions are relaxed by RFC 1440 (#33156), which is implemented, but feature-gated.
However, creating `UnsafeCell` from constants is unstable, so users can just enable the feature gate.
doc: Update reference with better description of target_env
The definition of this value recently changed slightly. It no
longer corresponds directly to the target triple.
Also shuffled things around to make the order of cfg descriptions more
logical and added text related them to the target triple.
cc #33403
rustdoc: add "src" links to individual impls
Since these impls can be scattered around quite a bit, it is nice to be able to jump to the location where individual methods and trait impls are defined.
NOTE: this needs an update to the CSS, which I'd like to leave for whoever is the "rustdoc frontend champion". The new [src] links are currently too large and bold. Also, the interaction with the "since version X" annotations is not good.
Fixes: #30416
parser: do not try to continue with `unsafe` on foreign fns
The changed line makes it look like `unsafe` is allowed, but the first statement of `parse_item_foreign_fn` is:
```
self.expect_keyword(keywords::Fn)?;
```
So we get the strange "expected one of `fn`, `pub`, `static`, or `unsafe`, found `unsafe`".
Fixes: #27361
std::thread docs: spawn() does not return a Thread anymore
Also move the "Thread type" section down a bit, since it is not so important anymore.
Fixes: #33321
mk: Fix building with --enable-ccache
We will no longer use `ccache` in the makefiles for our local dependencies like
miniz, but they're so small anyway it doesn't really matter.
Closes#33285
dep_graph: avoid panicking in thread when channel closed
On my system, when the processor is already loaded, and I try to
run the test suite, e.g. compile-fail/dep-graph-assoc-type-trans.rs
fails because of undecodable JSON.
Running the compiler manually, I can see that the dep graph thread
panics (and puts non-JSON on stderr) while `send`ing on `swap_out`,
presumably because the other end has already quit. I think that in
this case, we can just gracefully exit the thread.
A few oversights happened while porting the example from docopt to
getopts. I retraced all the steps, fixing code and description as
necessary.
Fixes: #33422
rustdoc: refactor rustdoc syntax highlighting for a more flexible API
Clients can now use the rustdoc syntax highlighter to classify tokens, then use that info to put together there own HTML (or whatever), rather than just having static HTML output.
parser: fix suppression of syntax errors in range RHS
Invalid expressions on the RHS were just swallowed without generating an error. The new version more closely mirrors the code for parsing `..x` in the `parse_prefix_range_expr` method below, where no cancel is done either.
Fixes#33262.
Move auxiliary directories to live with the tests
This is a step for enabling testing of cross-crate incremental compilation. The idea is that instead of having a central auxiliary directory, when you have a `// aux-build:foo.rs` annotation in the test `run-pass/bar.rs`, it will look in (e.g.) `run-pass/aux/foo.rs`. In general, it looks for an `aux` directory in the same directory as the test. We also ignore the `aux` directories when enumerating the set of tests.
As part of this PR, also refactor `runtest.rs` to use methods on a context, which means we can stop passing around context everywhere.
r? @alexcrichton
