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.
Because of type inference, duplicate obligations exist and cause duplicate
errors. To avoid this, only display the first error for each (predicate,span).
The inclusion of the span is somewhat bikesheddy, but *is* the more
conservative option (it does not remove some instability, as duplicate
obligations are ignored by `duplicate_set` under some inference conditions).
Fixes#28098
cc #21528 (is it a dupe?)
This lint warning was originally intended to help against misuse of the old Rust
`int` and `uint` types in FFI bindings where the Rust `int` was not equal to the
C `int`. This confusion no longer exists (as Rust's types are now `isize` and
`usize`), and as a result the need for this lint has become much less over time.
Additionally, starting with [the RFC for libc][rfc] it's likely that `isize` and
`usize` will be quite common in FFI bindings (e.g. they're the definition of
`size_t` and `ssize_t` on many platforms).
[rfc]: https://github.com/rust-lang/rfcs/pull/1291
This commit disables these lints to instead consider `isize` and `usize` valid
types to have in FFI signatures.
new error style:
```
path.rs:4:6: 4:7 error: the trait `core::marker::Sized` is not implemented for the type `[u8]` [E0277]
path.rs:4 fn f(p: Path) {}
^
path.rs:4:6: 4:7 help: run `rustc --explain E0277` to see a detailed explanation
path.rs:4:6: 4:7 note: `[u8]` does not have a constant size known at compile-time
path.rs:4:6: 4:7 note: required because it appears within the type `std::sys::os_str::Slice`
path.rs:4:6: 4:7 note: required because it appears within the type `std::ffi::os_str::OsStr`
path.rs:4:6: 4:7 note: required because it appears within the type `std::path::Path`
path.rs:4:6: 4:7 note: all local variables must have a statically known size
path.rs:7:5: 7:36 error: the trait `core::marker::Send` is not implemented for the type `alloc::rc::Rc<()>` [E0277]
path.rs:7 foo::<BTreeMap<Rc<()>, Rc<()>>>();
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
path.rs:7:5: 7:36 help: run `rustc --explain E0277` to see a detailed explanation
path.rs:7:5: 7:36 note: `alloc::rc::Rc<()>` cannot be sent between threads safely
path.rs:7:5: 7:36 note: required because it appears within the type `collections::btree::node::Node<alloc::rc::Rc<()>, alloc::rc::Rc<()>>`
path.rs:7:5: 7:36 note: required because it appears within the type `collections::btree::map::BTreeMap<alloc::rc::Rc<()>, alloc::rc::Rc<()>>`
path.rs:7:5: 7:36 note: required by `foo`
error: aborting due to 2 previous errors
```
Fixes#21793Fixes#23286
r? @nikomatsakis
The second commit in this PR will stop printing the macro definition site in backtraces, which cuts their length in half and increases readability (the definition site was only correct for local macros).
The third commit will not print an invocation if the last one printed occurred at the same place (span). This will make backtraces caused by a self-recursive macro much shorter.
(A possible alternative would be to capture the backtrace first, then limit it to a few frames at the start and end of the chain and print `...` inbetween. This would also work with multiple macros calling each other, which is not addressed by this PR - although the backtrace will still be halved)
Example:
```rust
macro_rules! m {
( 0 $($t:tt)* ) => ( m!($($t)*); );
() => ( fn main() {0} );
}
m!(0 0 0 0 0 0 0 0 0 0 0 0 0 0 0);
```
On a semi-recent nightly, this yields:
```
test.rs:3:21: 3:22 error: mismatched types:
expected `()`,
found `_`
(expected (),
found integral variable) [E0308]
test.rs:3 () => ( fn main() {0} );
^
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:2:23: 2:34 note: expansion site
test.rs:1:1: 4:2 note: in expansion of m!
test.rs:6:1: 6:35 note: expansion site
test.rs:3:21: 3:22 help: run `rustc --explain E0308` to see a detailed explanation
error: aborting due to previous error
```
After this patch:
```
test.rs:3:21: 3:22 error: mismatched types:
expected `()`,
found `_`
(expected (),
found integral variable) [E0308]
test.rs:3 () => ( fn main() {0} );
^
test.rs:2:23: 2:34 note: in this expansion of m!
test.rs:6:1: 6:35 note: in this expansion of m!
test.rs:3:21: 3:22 help: run `rustc --explain E0308` to see a detailed explanation
error: aborting due to previous error
```
This patch transforms functions of the form
```
fn f<Generic: AsRef<Concrete>>(arg: Generic) {
let arg: &Concrete = arg.as_ref();
// Code using arg
}
```
to the next form:
```
#[inline]
fn f<Generic: AsRef<Concrete>>(arg: Generic) {
fn f_inner(arg: &Concrete) {
// Code using arg
}
f_inner(arg.as_ref());
}
```
Therefore, most of the code is concrete and not duplicated during monomorphisation (unless inlined)
and only the tiny bit of conversion code is duplicated. This method was mentioned by @aturon in the
Conversion Traits RFC (https://github.com/rust-lang/rfcs/blame/master/text/0529-conversion-traits.md#L249) and similar techniques are not uncommon in C++ template libraries.
This patch goes to the extremes and applies the transformation even to smaller functions<sup>1</sup>
for purity of the experiment. *Some of them can be rolled back* if considered too ridiculous.
<sup>1</sup> However who knows how small are these functions are after inlining and everything.
The functions in question are mostly `fs`/`os` functions and not used especially often with variety
of argument types, so the code size reduction is rather small (but consistent). Here are the sizes
of stage2 artifacts before and after the patch:
https://gist.github.com/petrochenkov/e76a6b280f382da13c5dhttps://gist.github.com/petrochenkov/6cc28727d5256dbdfed0
Note:
All the `inner` functions are concrete and unavailable for cross-crate inlining, some of them may
need `#[inline]` annotations in the future.
r? @aturon
Overflows in integer pow() computations would be missed if they
preceded a 0 bit of the exponent being processed. This made
calls such as 2i32.pow(1024) not trigger an overflow.
Fixes#28012
This allows to skip the codegen for all the unneeded landing pads, reducing code size across the board by about 2-5%, depending on the crate. Compile times seem to be pretty unaffected though :-/
Unwinding across an FFI boundary is undefined behaviour, so we can mark
all external function as nounwind. The obvious exception are those
functions that actually perform the unwinding.
