This fixes#29048 (though I think adding better transactional support would be a better fix for that issue, but that is more difficult). It also simplifies region inference and changes the model to a pure data flow one, as discussed in [this internals thread](https://internals.rust-lang.org/t/rough-thoughts-on-the-impl-of-region-inference-mir-etc/2800). I am not 100% sure though if this PR is the right thing to do -- or at least maybe not at this moment, so thoughts on that would be appreciated.
r? @pnkfelix
cc @arielb1
expansion already by growing the RHS to be bigger than LHS (all the way
to `'static` if necessary). This is needed because contraction doesn't
handle givens. Fixes#28934.
empty region, and they complicate region inference to no particular end.
They also lead in some cases to spurious errors like #29048 (though in
some cases these errors are helpful in tracking down missing
constraints).
Closes#29314
The code from #29314:
```rust
fn main() {
if let Some(b) = None {
()
} else {
1
};
}
```
now prints this:
```
test.rs:2:5: 6:6 error: `if let` arms have incompatible types: expected `()`, found `_` (expected (), found integral variable) [E0308]
test.rs:2 if let Some(b) = None {
test.rs:3 ()
test.rs:4 } else {
test.rs:5 1
test.rs:6 };
test.rs:2:5: 6:6 help: run `rustc --explain E0308` to see a detailed explanation
test.rs:4:12: 6:6 note: `if let` arm with an incompatible type
test.rs:4 } else {
test.rs:5 1
test.rs:6 };
error: aborting due to previous error
```
this has the funky side-effect of also allowing constant evaluation of function calls to functions that are not `const fn` as long as `check_const` didn't mark that function `NOT_CONST`
It's still not possible to call a normal function from a `const fn`, but let statements' initialization value can get const evaluated (this caused the fallout in the overflowing tests)
we can now do this:
```rust
const fn add(x: usize, y: usize) -> usize { x + y }
const ARR: [i32; add(1, 2)] = [5, 6, 7];
```
also added a test for destructuring in const fn args
```rust
const fn i((a, b): (u32, u32)) -> u32 { a + b } //~ ERROR: E0022
```
This is a **[breaking change]**, since it turns some runtime panics into compile-time errors. This statement is true for ANY improvement to the const evaluator.
This commit stabilizes and deprecates library APIs whose FCP has closed in the
last cycle, specifically:
Stabilized APIs:
* `fs::canonicalize`
* `Path::{metadata, symlink_metadata, canonicalize, read_link, read_dir, exists,
is_file, is_dir}` - all moved to inherent methods from the `PathExt` trait.
* `Formatter::fill`
* `Formatter::width`
* `Formatter::precision`
* `Formatter::sign_plus`
* `Formatter::sign_minus`
* `Formatter::alternate`
* `Formatter::sign_aware_zero_pad`
* `string::ParseError`
* `Utf8Error::valid_up_to`
* `Iterator::{cmp, partial_cmp, eq, ne, lt, le, gt, ge}`
* `<[T]>::split_{first,last}{,_mut}`
* `Condvar::wait_timeout` - note that `wait_timeout_ms` is not yet deprecated
but will be once 1.5 is released.
* `str::{R,}MatchIndices`
* `str::{r,}match_indices`
* `char::from_u32_unchecked`
* `VecDeque::insert`
* `VecDeque::shrink_to_fit`
* `VecDeque::as_slices`
* `VecDeque::as_mut_slices`
* `VecDeque::swap_remove_front` - (renamed from `swap_front_remove`)
* `VecDeque::swap_remove_back` - (renamed from `swap_back_remove`)
* `Vec::resize`
* `str::slice_mut_unchecked`
* `FileTypeExt`
* `FileTypeExt::{is_block_device, is_char_device, is_fifo, is_socket}`
* `BinaryHeap::from` - `from_vec` deprecated in favor of this
* `BinaryHeap::into_vec` - plus a `Into` impl
* `BinaryHeap::into_sorted_vec`
Deprecated APIs
* `slice::ref_slice`
* `slice::mut_ref_slice`
* `iter::{range_inclusive, RangeInclusive}`
* `std::dynamic_lib`
Closes#27706Closes#27725
cc #27726 (align not stabilized yet)
Closes#27734Closes#27737Closes#27742Closes#27743Closes#27772Closes#27774Closes#27777Closes#27781
cc #27788 (a few remaining methods though)
Closes#27790Closes#27793Closes#27796Closes#27810
cc #28147 (not all parts stabilized)
This commit stabilizes and deprecates library APIs whose FCP has closed in the
last cycle, specifically:
Stabilized APIs:
* `fs::canonicalize`
* `Path::{metadata, symlink_metadata, canonicalize, read_link, read_dir, exists,
is_file, is_dir}` - all moved to inherent methods from the `PathExt` trait.
* `Formatter::fill`
* `Formatter::width`
* `Formatter::precision`
* `Formatter::sign_plus`
* `Formatter::sign_minus`
* `Formatter::alternate`
* `Formatter::sign_aware_zero_pad`
* `string::ParseError`
* `Utf8Error::valid_up_to`
* `Iterator::{cmp, partial_cmp, eq, ne, lt, le, gt, ge}`
* `<[T]>::split_{first,last}{,_mut}`
* `Condvar::wait_timeout` - note that `wait_timeout_ms` is not yet deprecated
but will be once 1.5 is released.
* `str::{R,}MatchIndices`
* `str::{r,}match_indices`
* `char::from_u32_unchecked`
* `VecDeque::insert`
* `VecDeque::shrink_to_fit`
* `VecDeque::as_slices`
* `VecDeque::as_mut_slices`
* `VecDeque::swap_remove_front` - (renamed from `swap_front_remove`)
* `VecDeque::swap_remove_back` - (renamed from `swap_back_remove`)
* `Vec::resize`
* `str::slice_mut_unchecked`
* `FileTypeExt`
* `FileTypeExt::{is_block_device, is_char_device, is_fifo, is_socket}`
* `BinaryHeap::from` - `from_vec` deprecated in favor of this
* `BinaryHeap::into_vec` - plus a `Into` impl
* `BinaryHeap::into_sorted_vec`
Deprecated APIs
* `slice::ref_slice`
* `slice::mut_ref_slice`
* `iter::{range_inclusive, RangeInclusive}`
* `std::dynamic_lib`
Closes#27706Closes#27725
cc #27726 (align not stabilized yet)
Closes#27734Closes#27737Closes#27742Closes#27743Closes#27772Closes#27774Closes#27777Closes#27781
cc #27788 (a few remaining methods though)
Closes#27790Closes#27793Closes#27796Closes#27810
cc #28147 (not all parts stabilized)
trait definitions, and give prefence to the former. This is consistent
with what we do for selection. It also works around a limitation
that was leading to #28871.
This PR turns statically known erroneous code (e.g. numeric overflow) into a warning and continues normal code-generation to emit the same code that would have been generated without `check_const` detecting that the result can be computed at compile-time.
<del>It's not done yet, as I don't know how to properly emit a lint from trans. I can't seem to extract the real lint level of the item the erroneous expression is in.</del> It's an unconditional warning now.
r? @pnkfelix
cc @nikomatsakis
* [RFC 1229 text](https://github.com/rust-lang/rfcs/blob/master/text/1229-compile-time-asserts.md)
* RFC PR: rust-lang/rfcs#1229
* tracking issue: https://github.com/rust-lang/rust/issues/28238
Stricter checking of stability attributes + enforcement of their invariants at compile time
(+ removed dead file librustc_front/attr.rs)
I intended to enforce use of `reason` for unstable items as well (it normally presents for new items), but it turned out too intrusive, many older unstable items don't have `reason`s.
r? @aturon
I'm studying how stability works and do some refactoring along the way, so it's probably not the last PR.
Here is my attempt to resolve issue #28822, @Manishearth.
Please let me know if it's fine. And if not, what should I do instead?
This issue felt like quite a good start for some rust contributions. It allows me to get used to the workflow and codebase of rust in an easy-to-swallow manner. Are there any other issues you would recommend me to look at? :) Would love to do some more stuff!
