The usecase is that functions made visible to systems outside of the
rust ecosystem require the symbol to be visible.
This adds a lint for functions that are not exported, but also not mangled.
It has some gotchas:
[ ]: There is fallout in core that needs taking care of
[ ]: I'm not convinced the error message is correct
[ ]: It has no tests
~~However, there's an underlying issue which I'd like feedback on- which is that my belief that that non-pub functions would not have their symbols exported, however that seems not to be the case in the first case that this lint turned up in rustc (`rust_fail`), which intuition suggests has been working.~~
This seems to be a separate bug in rust, wherein the symbols are exported in binaries, but not in rlibs or dylibs. This lint would catch that case.
As per [RFC #235][rfc], you can now do:
[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0235-collections-conventions.md#intoiterator-and-iterable
``` rust
let mut v = vec![1];
// iterate over immutable references
for x in &v {
assert_eq!(x, &1);
}
// iterate over mutable references
for x in &mut v {
assert_eq!(x, &mut 1);
}
// iterate over values, this consumes `v`
for x in v {
assert_eq!(x, 1);
}
```
[breaking-change]s
For loops now "consume" (move) the iterator, this breaks iterating over mutable references to iterators, and also breaks multiple iterations over the same iterator:
``` rust
fn foo(mut it: &mut Iter) { // `Iter` implements `Iterator`
for x in it { .. } //~ error: `&mut Iter` doesn't implement Iterator
}
fn bar() {
for x in it { .. } //~ note: `it` moved here
for x in it { .. } //~ error: `it` has been moved
}
```
Both cases can be fixed using the `by_ref()` adapter to create an iterator from the mutable reference:
``` rust
fn foo(mut it: &mut Iter) {
for x in it.by_ref() { .. }
}
fn bar() {
for x in it.by_ref() { .. }
for x in it { .. }
}
```
This PR also makes iterator non-implicitly copyable, as this was source of subtle bugs in the libraries. You can still use `clone()` to explictly copy the iterator.
Finally, since the for loops are implemented in the frontend and use global paths to `IntoIterator`, `Iterator` and `Option` variants, users of the `core` crate will have to use add an `std` module to the root of their crate to be able to use for loops:
``` rust
#![no_std]
extern crate core;
fn main() {
for x in 0..10 {}
}
#[doc(hidden)]
mod std {
// these imports are needed to use for-loops
pub use core::iter;
pub use core::option;
}
```
---
r? @nikomatsakis @aturon
cc #18424closes#18045
The usecase is that functions made visible to systems outside of the
rust ecosystem require the symbol to be visible.
This adds a lint for functions that are not exported, but also not mangled.
It has some gotchas:
[ ]: There is fallout in core that needs taking care of
[ ]: I'm not convinced the error message is correct
[ ]: It has no tests
~~However, there's an underlying issue which I'd like feedback on- which is that my belief that that non-pub functions would not have their symbols exported, however that seems not to be the case in the first case that this lint turned up in rustc (`rust_fail`), which intuition suggests has been working.~~
This seems to be a separate bug in rust, wherein the symbols are exported in binaries, but not in rlibs or dylibs. This lint would catch that case.
This commit performs a final stabilization pass over the std::fmt module,
marking all necessary APIs as stable. One of the more interesting aspects of
this module is that it exposes a good deal of its runtime representation to the
outside world in order for `format_args!` to be able to construct the format
strings. Instead of hacking the compiler to assume that these items are stable,
this commit instead lays out a story for the stabilization and evolution of
these APIs.
There are three primary details used by the `format_args!` macro:
1. `Arguments` - an opaque package of a "compiled format string". This structure
is passed around and the `write` function is the source of truth for
transforming a compiled format string into a string at runtime. This must be
able to be constructed in stable code.
2. `Argument` - an opaque structure representing an argument to a format string.
This is *almost* a trait object as it's just a pointer/function pair, but due
to the function originating from one of many traits, it's not actually a
trait object. Like `Arguments`, this must be constructed from stable code.
3. `fmt::rt` - this module contains the runtime type definitions primarily for
the `rt::Argument` structure. Whenever an argument is formatted with
nonstandard flags, a corresponding `rt::Argument` is generated describing how
the argument is being formatted. This can be used to construct an
`Arguments`.
The primary interface to `std::fmt` is the `Arguments` structure, and as such
this type name is stabilize as-is today. It is expected for libraries to pass
around an `Arguments` structure to represent a pending formatted computation.
The remaining portions are largely "cruft" which would rather not be stabilized,
but due to the stability checks they must be. As a result, almost all pieces
have been renamed to represent that they are "version 1" of the formatting
representation. The theory is that at a later date if we change the
representation of these types we can add new definitions called "version 2" and
corresponding constructors for `Arguments`.
One of the other remaining large questions about the fmt module were how the
pending I/O reform would affect the signatures of methods in the module. Due to
[RFC 526][rfc], however, the writers of fmt are now incompatible with the
writers of io, so this question has largely been solved. As a result the
interfaces are largely stabilized as-is today.
[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0526-fmt-text-writer.md
Specifically, the following changes were made:
* The contents of `fmt::rt` were all moved under `fmt::rt::v1`
* `fmt::rt` is stable
* `fmt::rt::v1` is stable
* `Error` is stable
* `Writer` is stable
* `Writer::write_str` is stable
* `Writer::write_fmt` is stable
* `Formatter` is stable
* `Argument` has been renamed to `ArgumentV1` and is stable
* `ArgumentV1::new` is stable
* `ArgumentV1::from_uint` is stable
* `Arguments::new_v1` is stable (renamed from `new`)
* `Arguments::new_v1_formatted` is stable (renamed from `with_placeholders`)
* All formatting traits are now stable, as well as the `fmt` method.
* `fmt::write` is stable
* `fmt::format` is stable
* `Formatter::pad_integral` is stable
* `Formatter::pad` is stable
* `Formatter::write_str` is stable
* `Formatter::write_fmt` is stable
* Some assorted top level items which were only used by `format_args!` were
removed in favor of static functions on `ArgumentV1` as well.
* The formatting-flag-accessing methods remain unstable
Within the contents of the `fmt::rt::v1` module, the following actions were
taken:
* Reexports of all enum variants were removed
* All prefixes on enum variants were removed
* A few miscellaneous enum variants were renamed
* Otherwise all structs, fields, and variants were marked stable.
In addition to these actions in the `std::fmt` module, many implementations of
`Show` and `String` were stabilized as well.
In some other modules:
* `ToString` is now stable
* `ToString::to_string` is now stable
* `Vec` no longer implements `fmt::Writer` (this has moved to `String`)
This is a breaking change due to all of the changes to the `fmt::rt` module, but
this likely will not have much impact on existing programs.
Closes#20661
[breaking-change]
This commits adds an associated type to the `FromStr` trait representing an
error payload for parses which do not succeed. The previous return value,
`Option<Self>` did not allow for this form of payload. After the associated type
was added, the following attributes were applied:
* `FromStr` is now stable
* `FromStr::Err` is now stable
* `FromStr::from_str` is now stable
* `StrExt::parse` is now stable
* `FromStr for bool` is now stable
* `FromStr for $float` is now stable
* `FromStr for $integral` is now stable
* Errors returned from stable `FromStr` implementations are stable
* Errors implement `Display` and `Error` (both impl blocks being `#[stable]`)
Closes#15138
Coercions will now attempt to autoderef as needed before reborrowing.
This includes overloaded `Deref`, e.g. `&Rc<T>` coerces to `&T`, and
`DerefMut`, e.g. `&mut Vec<T>` coerces to `&mut [T]` (in addition to `&[T]`).
Closes#21432.
