Warn about unused expressions with closure or generator type. This follows
existing precedence of must use annotations present on `FnOnce`, `FnMut`, `Fn`
traits, which already indirectly apply to closures in some cases, e.g.,:
```rust
fn f() -> impl FnOnce() {
|| {}
}
fn main() {
// an existing warning: unused implementer of `std::ops::FnOnce` that must be used:
f();
// a new warning: unused closure that must be used:
|| {};
}
```
Derive common traits for panic::Location.
Now that `#[track_caller]` is on track to stabilize, one of the roughest edges of working with it is the fact that you can't do much with `Location` except turn it back into a `(&str, u32, u32)`. Which makes sense because the type was defined around the panic machinery originally passing around that tuple (it has the same layout as Location even).
This PR derives common traits for the type in accordance with the [API guidelines](https://rust-lang.github.io/api-guidelines/interoperability.html#types-eagerly-implement-common-traits-c-common-traits) (those apply to core, right?).
There's a risk here, e.g. if we ever change the representation of `Location` in a way that makes it harder to implement `Ord`, we might not be able to make that change in a backwards-compatible way. I don't think there's any other compatibility hazard here, as the only changes we currently imagine for the type are to add end fields.
cc @rust-lang/libs
More ensure stack to avoid segfault with increased `recursion_limit`
Fixes#74711
I do not add the test here since the limit value depends on the machine and it's hard to test the output.
r? @oli-obk
rustbuild: fix bad usage of UNIX exec() in rustc wrapper
exec never returns, it replaces the current process. so anything after it is unreachable. that's not how exec_cmd() is used in the surrounding code
We use `--on-fail env` on Debian. `env` always returns exit code 0. This means that the `rustc` bootstrap wrapper always returns exit code 0 even when it fails. However, the crossbeam-utils build process (due to autocfg) relies on `rustc` returning error exit codes when detecting CPU features, and ends up writing `cargo:rustc-cfg=has_atomic_u128` even when it's not detected, because the `rustc` wrapper is always giving exit code 0.
(This separately is causing our builds to try to compile rustc 40+ times, due to #74801.)
Forbid generic parameters in anon consts inside of type defaults
Emit a resolution error for `struct Foo<T, U = [u8; std::mem::size_of::<T>()]>`.
We are unable to support this with the way `ty::Generics` is currently used,
so let's just forbid it entirely for now.
Fixes some ICE on stable, e.g.
```rust
struct Foo<T, U = [u8; std::mem::size_of::<*mut T>()]>(T, U);
```
r? @varkor @eddyb
