Improve is_empty on the VecDeque and its iterators by just comparing
tail and head; this saves a few instructions (to be able to remove the
`& (size - 1)` computation, it would have to know that size is a power of two).
in region, treat current (and future) item-likes alike
The `visit_fn` code mutates its surrounding context. Between *items*,
this was saved/restored, but between impl items it was not. This meant
that we wound up with `CallSiteScope` entries with two parents (or
more!). As far as I can tell, this is harmless in actual type-checking,
since the regions you interact with are always from at most one of those
branches. But it can slow things down.
Before, the effect was limited, since it only applied to impl items
within an impl. After #37660, impl items are visisted all together at
the end, and hence this could create a very messed up
hierarchy. Isolating impl item properly solves both issues.
I cannot come up with a way to unit-test this; for posterity, however,
you can observe the messed up hierarchies with a test as simple as the
following, which would create a callsite scope with two parents both
before and after
```
struct Foo {
}
impl Foo {
fn bar(&self) -> usize {
22
}
fn baz(&self) -> usize {
22
}
}
fn main() { }
```
Fixes#37864.
r? @michaelwoerister
cc @pnkfelix -- can you think of a way to make a regr test?
add a `-Z incremental-dump-hash` flag
This causes us to dump a bunch of has information to stdout that can be
useful in tracking down incremental compilation invalidations,
particularly across crates.
incr.comp.: Add more output to -Z incremental-info.
Also makes sure that all output from `-Z incremental-info` is prefixed with `incremental:` for better grep-ability.
r? @nikomatsakis
Show `Trait` instead of `<Struct as Trait>` in E0323
For a given file
```
trait Foo {
fn bar(&self);
}
pub struct FooConstForMethod;
impl Foo for FooConstForMethod {
const bar: u64 = 1;
}
```
show
```
error[E0323]: item `bar` is an associated const, which doesn't match its trait `Foo`
```
instead of
```
error[E0323]: item `bar` is an associated const, which doesn't match its trait `<FooConstForMethod as Foo>`
```
Fix#37618
Refactor one_bound_for_assoc_type to take an Iterator instead of Vec
I doubt the performance implications will be serious, but it will avoid allocating one-element Vecs for the successful case (and avoid allocating vecs at all for any case, too).
`--stage 2` tests passed locally.
Add new #[target_feature = "..."] attribute.
This commit adds a new attribute that instructs the compiler to emit
target specific code for a single function. For example, the following
function is permitted to use instructions that are part of SSE 4.2:
#[target_feature = "+sse4.2"]
fn foo() { ... }
In particular, use of this attribute does not require setting the
-C target-feature or -C target-cpu options on rustc.
This attribute does not have any protections built into it. For example,
nothing stops one from calling the above `foo` function on hosts without
SSE 4.2 support. Doing so may result in a SIGILL.
I've also expanded the x86 target feature whitelist.
print option to dump target spec as JSON
This lets the user dump out the target spec that the compiler is using. This is useful to people defining their own target.json to compare it against existing targets or understand how different targets change internal settings. It is also potentially useful for Cargo to determine if something has changed with a target and it needs to rebuild things.
evaluate obligations in LIFO order during closure projection
This is an annoying gotcha with the projection cache's handling of
nested obligations.
Nested projection obligations enter the issue in this case:
```
DEBUG:rustc::traits::project: AssociatedTypeNormalizer: depth=3
normalized
<std::iter::Map<std::ops::Range<i32>,
[closure@not-a-recursion-error.rs:5:30: 5:53]> as
std::iter::IntoIterator>::Item to _#7t with 12 add'l obligations
```
Here the normalization result is the result of the nested impl
`<[closure@not-a-recursion-error.rs:5:30: 5:53] as FnMut(i32)>::Output`,
which is an additional obligation that is a part of "add'l obligations".
By itself, this is proper behaviour - the additional obligation is
returned, and the RFC 447 rules ensure that it is processed before the
output `#_7t` is used in any way.
However, the projection cache breaks this - it caches the
`<std::iter::Map<std::ops::Range<i32>,[closure@not-a-recursion-error.rs:5:30:
5:53]> as std::iter::IntoIterator>::Item = #_7t` resolution. Now
everybody else that attempts to look up the projection will just get
`#_7t` *without* any additional obligations. This obviously causes all
sorts of trouble (here a spurious `EvaluatedToAmbig` results in
specializations not being discarded
[here](9ca50bd4d5/src/librustc/traits/select.rs (L1705))).
The compiler works even with this projection cache gotcha because in most
cases during "one-pass evaluation". we tend to process obligations in LIFO
order - after an obligation is added to the cache, we process its nested
obligations before we do anything else (and if we have a cycle, we handle
it specifically) - which makes sure the inference variables are resolved
before they are used.
That "LIFO" order That was not done when projecting out of a closure, so
let's just fix that for the time being.
Fixes#38033.
Beta-nominating because regression.
r? @nikomatsakis
In LLVM 4.0, this enum becomes an actual type-safe enum, which breaks
all of the interfaces. Introduce our own copy of the bitflags that we
can then safely convert to the LLVM one.
It is an unnecessary restriction; nth neither needs self to be sized
nor needs to be exempted from the trait object.
It increases the utility of the nth method, because type specific
implementations are available through `&mut I` or through an iterator
trait object.
It is a backwards compatible change due to the special cases of the
`where Self: Sized` bound; it was already optional to include this bound
in `Iterator` implementations.
