We are heading towards deeper integration with the region inference
system in infcx; in particular, prior to the creation of the
`RegionInferenceContext`, it will be the "owner" of the set of region
variables.
check_unsafety: fix unused unsafe block duplication
The duplicate error message is later removed by error message
deduplication, but it still appears on beta and is still a bug.
r? @eddyb
always add an unreachable branch on matches to give more info to llvm
As part of https://github.com/djzin/rustc-optimization I discovered that some simple enum optimizations (src/unary/three_valued_enum.rs and src/unary/four_valued_enum.rs in the repo) are not applied - and the reason for this is that we erase the info that the discriminant of an enum is one of the options by putting the last one in an "otherwise" branch. This patch adds an extra branch so that LLVM can know what the possibilities are for the discriminant, which fixes the three- and four- valued cases.
Note that for whatever reason, this doesn't fix the case of 2 variants (most notably `Option` and `Result` have 2 variants) - a pass re-ordering might fix this or we may wish to add "assume" annotations on discriminants to force it to optimize.
MIR-borrowck: don't ICE for cannot move from array error
Closes#45694
compile-fail test E0508 now gives
```text
error[E0508]: cannot move out of type `[NonCopy; 1]`, a non-copy array (Ast)
--> .\src\test\compile-fail\E0508.rs:18:18
|
18 | let _value = array[0]; //[ast]~ ERROR E0508
| ^^^^^^^^
| |
| cannot move out of here
| help: consider using a reference instead: `&array[0]`
error[E0508]: cannot move out of type `[NonCopy; 1]`, a non-copy array (Mir)
--> .\src\test\compile-fail\E0508.rs:18:18
|
18 | let _value = array[0]; //[ast]~ ERROR E0508
| ^^^^^^^^ cannot move out of here
error: aborting due to 2 previous errors
```
MIR-borrowck: fix diagnostics for closures
Emit notes for captured variables in the same manner as AST borrowck.
```
error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
--> $DIR/borrowck-closures-two-mut.rs:24:24
|
23 | let c1 = to_fn_mut(|| x = 4);
| -- - previous borrow occurs due to use of `x` in closure
| |
| first mutable borrow occurs here
24 | let c2 = to_fn_mut(|| x = 5); //~ ERROR cannot borrow `x` as mutable more than once
| ^^ - borrow occurs due to use of `x` in closure
| |
| second mutable borrow occurs here
25 | }
| - first borrow ends here
error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
--> $DIR/borrowck-closures-two-mut.rs:24:24
|
23 | let c1 = to_fn_mut(|| x = 4);
| -- - previous borrow occurs due to use of `x` in closure
| |
| first mutable borrow occurs here
24 | let c2 = to_fn_mut(|| x = 5); //~ ERROR cannot borrow `x` as mutable more than once
| ^^ - borrow occurs due to use of `x` in closure
| |
| second mutable borrow occurs here
25 | }
| - first borrow ends here
```
Fixes#45362.
Fix MIR CopyPropagation errneously propagating assignments to function args
Compiling this code with MIR CopyPropagation activated will result in printing `5`,
because CopyProp errneously propagates the assignment of `5` to all `x`:
```rust
fn bar(mut x: u8) {
println!("{}", x);
x = 5;
}
fn main() {
bar(123);
}
```
If a local is propagated, it will result in an ICE at trans due to an use-before-def:
```rust
fn dummy(x: u8) -> u8 { x }
fn foo(mut x: u8) {
x = dummy(x); // this will assign a local to `x`
}
```
Currently CopyProp conservatively gives up if there are multiple assignments to a local,
but it is not took into account that arguments are already assigned from the beginning.
This PR fixes the problem by preventing propagation of assignments to function arguments.
