[MIR] SwitchInt Everywhere
Something I've been meaning to do for a very long while. This PR essentially gets rid of 3 kinds of conditional branching and only keeps the most general one - `SwitchInt`. Primary benefits are such that dealing with MIR now does not involve dealing with 3 different ways to do conditional control flow. On the other hand, constructing a `SwitchInt` currently requires more code than what previously was necessary to build an equivalent `If` terminator. Something trivially "fixable" with some constructor methods somewhere (MIR needs stuff like that badly in general).
Some timings (tl;dr: slightly faster^1 (unexpected), but also uses slightly more memory at peak (expected)):
^1: Not sure if the speed benefits are because of LLVM liking the generated code better or the compiler itself getting compiled better. Either way, its a net benefit. The CORE and SYNTAX timings done for compilation without optimisation.
```
AFTER:
Building stage1 std artifacts (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
Finished release [optimized] target(s) in 31.50 secs
Finished release [optimized] target(s) in 31.42 secs
Building stage1 compiler artifacts (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
Finished release [optimized] target(s) in 439.56 secs
Finished release [optimized] target(s) in 435.15 secs
CORE: 99% (24.81 real, 0.13 kernel, 24.57 user); 358536k resident
CORE: 99% (24.56 real, 0.15 kernel, 24.36 user); 359168k resident
SYNTAX: 99% (49.98 real, 0.48 kernel, 49.42 user); 653416k resident
SYNTAX: 99% (50.07 real, 0.58 kernel, 49.43 user); 653604k resident
BEFORE:
Building stage1 std artifacts (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
Finished release [optimized] target(s) in 31.84 secs
Building stage1 compiler artifacts (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
Finished release [optimized] target(s) in 451.17 secs
CORE: 99% (24.66 real, 0.20 kernel, 24.38 user); 351096k resident
CORE: 99% (24.36 real, 0.17 kernel, 24.18 user); 352284k resident
SYNTAX: 99% (52.24 real, 0.56 kernel, 51.66 user); 645544k resident
SYNTAX: 99% (51.55 real, 0.48 kernel, 50.99 user); 646428k resident
```
cc @nikomatsakis @eddyb
Previously it used to build a switch in a way that didn’t preserve the invariat of SwitchInt. Now
it builds it in an optimal way too, where otherwise branch becomes all the branches which did not
have partial variant drops.
This removes another special case of Switch by replacing it with the more general SwitchInt. While
this is more clunky currently, there’s no reason we can’t make it nice (and efficient) to use.
Previously AdtDef variants contained ConstInt for each discriminant, which did not really reflect
the actual type of the discriminants. Moving the type into AdtDef allows to easily put the type
into metadata and also saves bytes from ConstVal overhead for each discriminant.
Also arguably the code is cleaner now :)
Make reprs use a structured representation instead of a slice
This is needed for `-z reorder-fields`. The old design uses a slice taken from HIR, plus a cache that lazily parses. The new design stores it directly in the `AdtDef` as a `ReprOptions`. We're doing this now because we need to be able to add reprs that don't necessarily exist in HIR for `-z reorder-fields`, but it needs to happen anyway.
`lookup_repr_hints` should be mostly deprecated. I want to remove it from `layout` before closing this, unless people think that should be a separate PR. The `[WIP]` is because of this. The problem with closing this as-is is that the code here isn't actually testable until some parts of the compiler start using it.
r? @eddyb
Stabilize static lifetime in statics
Stabilize the "static_in_const" feature. Blockers before this PR can be merged:
* [x] The [FCP with inclination to stabilize](https://github.com/rust-lang/rust/issues/35897#issuecomment-270441437) needs to be over. FCP lasts roughly three weeks, so will be over at Jan 25, aka this thursday.
* [x] Documentation needs to be added (#37928)
Closes#35897.
Improve error message for uninferrable types #38812
Hello,
I tried to improve the error message for uninferrable types. The error code is `E0282`.
```rust
error[E0282]: type annotations needed
--> /home/cengizIO/issue38812.rs:2:11
|
2 | let x = vec![];
| - ^^^^^^ cannot infer type for `T`
| |
| consider giving `x` a type
|
= note: this error originates in a macro outside of the current crate
```
and
```rust
error[E0282]: type annotations needed
--> /home/cengizIO/issue38812.rs:2:15
|
2 | let (x,) = (vec![],);
| ---- ^^^^^^ cannot infer type for `T`
| |
| consider giving a type to pattern
|
= note: this error originates in a macro outside of the current crate
```
Rust compiler now tries to find uninferred `local`s with type `_` and adds them into the error message.
I'm probably wrong on wording that I used. Please feel free to suggest better alternatives.
Thanks @nikomatsakis for mentoring 🍺
Any comments/feedback is more than welcome!
Thank you
make lifetimes that only appear in return type early-bound
This is the full and proper fix for #32330. This also makes some effort to give a nice error message (as evidenced by the `ui` test), sending users over to the tracking issue for a fuller explanation and offering a `--explain` message in some cases.
This needs a crater run before we land.
r? @arielb1
This is the full and proper fix for #32330. This also makes some effort
to give a nice error message (as evidenced by the `ui` test), sending
users over to the tracking issue for a full explanation.
Add warning for () to ! switch
With feature(never_type) enabled diverging type variables will default to `!` instead of `()`. This can cause breakages where a trait is resolved on such a type.
This PR emits a future-compatibility warning when it sees this happen.
rustdoc: fix doctests with non-feature crate attrs
Fixes#38129.
The book says that any top-level crate attributes at the beginning of a doctest are moved outside the generated `fn main`, but it was only checking for `#![feature`, not `#![`.
These attributes previously caused warnings but were then ignored, so in theory this could change the behavior of doctests in the wild.
Implement kind="static-nobundle" (RFC 1717)
This implements the "static-nobundle" library kind (last item from #37403).
Rustc handles "static-nobundle" libs very similarly to dylibs, except that on Windows, uses of their symbols do not get marked with "dllimport". Which is the whole point of this feature.
Previously, the note/message for the source of a lint being the command
line unconditionally named the individual lint, even if the actual
command specified a lint group (e.g., `-D warnings`); here, we take note
of the actual command options so we can be more specific.
This remains in the matter of #36846.
Warning or error messages set via a lint group attribute
(e.g. `#[deny(warnings)]`) should still make it clear which individual
lint (by name) was triggered, similarly to how we include "on by
default" language for default lints. This—and, while we're here, the
existing "on by default" language—can be tucked into a note rather than
cluttering the main error message. This occasions the slightest of
refactorings (we now have to get the diagnostic-builder with the main
message first, before matching on the lint source).
This is in the matter of #36846.
Miscellaneous refactors around how lints and typeck interact
This is preparation for making incr. comp. skip typeck. The main gist of is trying to rationalize the outputs from typeck that are not part of tables:
- one bit of output is the `used_trait_imports` set, which becomes something we track for dependencies
- the other big of output are various lints; we used to store these into a table on sess, but this work stores them into the`TypeckTables`, and then makes the lint pass consult that
- I think it probably makes sense to handle errors similarly, eventually, but that's not necessary now
r? @eddyb
Fixes#39495
