When encountering code like the following, suggest borrowing the for loop
head to avoid moving it into the for loop pattern:
```
fn main() {
let a = vec![1, 2, 3];
for i in &a {
for j in a {
println!("{} * {} = {}", i, j, i * j);
}
}
}
```
Rollup of 7 pull requests
Successful merges:
- #59213 (Track changes to robots.txt)
- #59239 (Remove inline assembly from hint::spin_loop)
- #59251 (Use a valid name for graphviz graphs)
- #59296 (Do not encode gensymed imports in metadata)
- #59328 (Implement specialized nth_back() for Box and Windows.)
- #59355 (Fix ICE with const generic param in struct)
- #59377 (Correct minimum system LLVM version in tests)
(WIP) Small fixes in chalkification
Small fixes around region constraints and builtin impls. There are still some type inference errors, for example the following code errors out:
```rust
fn main() {
let mut x: Vec<i32> = Vec::new();
// ^^^^^^^^ cannot infer type for `std::vec::Vec<_>`
}
```
but explicitly specifying `Vec::<i32>::new` works.
With these few fixes, the following code now passes type-checking:
```rust
fn main() {
let mut x: Vec<i32> = Vec::<i32>::new();
x.push(5);
println!("{:?}", x);
}
```
I also fixed the implied bounds bug as discussed on Zulip and in https://github.com/rust-lang-nursery/chalk/pull/206
cc @tmandry
r? @nikomatsakis
Do not encode gensymed imports in metadata
(Unless they are underscore `_` imports which are re-gensymed on crate loading, see https://github.com/rust-lang/rust/pull/56392.)
We cannot encode gensymed imports properly in metadata and if we encode them improperly, we can get erroneous name conflicts downstream.
Gensymed imports are produced by the compiler, so we control their set, and can be sure that none of them needs being encoded for use from other crates.
A workaround that fixes https://github.com/rust-lang/rust/issues/59243.
Remove `track_errors` from `check_match`, `typeck_item_bodies` and `register_plugins`
In the spirit of continuing through errors in type checking (#39275), remove `track_errors` from a couple of locations in the codebase.
In order to minimize the verbosity of common syntax errors that are parsed
as type ascription, hide the feature gate error unless there are no other
errors being emitted by the parser.
Do not complain about non-existing fields after parse recovery
When failing to parse struct-like enum variants, the ADT gets recorded
as having no fields. Record that we have actually recovered during
parsing of this variant to avoid complaing about non-existing fields
when actually using it.
Fix#57361.
consistent naming for Rhs type parameter in libcore/ops
Rename RHS type parameter occurrences RHS->Rhs to make it consistent throughout files and follow naming conventions.
Point at coercion reason for `if` expressions without else clause if caused by return type
```
error[E0317]: if may be missing an else clause
--> $DIR/if-without-else-as-fn-expr.rs:2:5
|
LL | fn foo(bar: usize) -> usize {
| ----- found `usize` because of this return type
LL | / if bar % 5 == 0 {
LL | | return 3;
LL | | }
| |_____^ expected (), found usize
|
= note: expected type `()`
found type `usize`
= note: `if` expressions without `else` must evaluate to `()`
```
Fix#25228.
