Fix 'associate type' typo
I came across an error message mentioning an 'associate type'.
Since this is the only instance of this term in rustc (it's 'associated type' everywhere else), I think this might be a typo.
Make assignments to `Copy` union fields safe
This is an accompanying PR to PR https://github.com/rust-lang/rust/pull/42068 stabilizing FFI unions.
This was first proposed in https://github.com/rust-lang/rust/issues/32836#issuecomment-281296416, see subsequent comments as well.
Assignments to `Copy` union fields do not read any data from the union and are [equivalent](https://github.com/rust-lang/rust/issues/32836#issuecomment-281660298) to whole union assignments, which are safe, so they should be safe as well. This removes a significant number of "false positive" unsafe blocks, in code dealing with FFI unions in particular.
It desirable to make this change now, together with stabilization of FFI unions, because now it affecfts only unstable code, but later it will cause warnings/errors caused by `unused_unsafe` lint in stable code.
cc #32836
r? @nikomatsakis
add thiscall calling convention support
This support is needed for bindgen to work well on 32-bit Windows, and also enables people to begin experimenting with C++ FFI support on that platform.
Fixes#42044.
Initial implementation of declarative macros 2.0
Implement declarative macros 2.0 (rust-lang/rfcs#1584) behind `#![feature(decl_macro)]`.
Differences from `macro_rules!` include:
- new syntax: `macro m(..) { .. }` instead of `macro_rules! m { (..) => { .. } }`
- declarative macros are items:
```rust
// crate A:
pub mod foo {
m!(); // use before definition; declaration order is irrelevant
pub macro m() {} // `pub`, `pub(super)`, etc. work
}
fn main() {
foo::m!(); // named like other items
{ use foo::m as n; n!(); } // imported like other items
}
pub use foo::m; // re-exported like other items
// crate B:
extern crate A; // no need for `#[macro_use]`
A::foo::m!(); A::m!();
```
- Racket-like hygiene for items, imports, methods, fields, type parameters, privacy, etc.
- Intuitively, names in a macro definition are resolved in the macro definition's scope, not the scope in which the macro is used.
- This [explaination](http://beautifulracket.com/explainer/hygiene.html) of hygiene for Racket applies here (except for the "Breaking Hygiene" section). I wrote a similar [explanation](https://github.com/jseyfried/rfcs/blob/hygiene/text/0000-hygiene.md) for Rust.
- Generally speaking, if `fn f() { <body> }` resolves, `pub macro m() { <body> } ... m!()` also resolves, even if `m!()` is in a separate crate.
- `::foo::bar` in a `macro` behaves like `$crate::foo::bar` in a `macro_rules!`, except it can access everything visible from the `macro` (thus more permissive).
- See [`src/test/{run-pass, compile-fail}/hygiene`](https://github.com/rust-lang/rust/pull/40847/commits/afe7d89858fd72b983e24727d6f4058293153c19) for examples. Small example:
```rust
mod foo {
fn f() { println!("hello world"); }
pub macro m() { f(); }
}
fn main() { foo::m!(); }
```
Limitations:
- This does not address planned changes to matchers (`expr`,`ty`, etc.), c.f. #26361.
- Lints (including stability and deprecation) and `unsafe` are not hygienic.
- adding hygiene here will be mostly or entirely backwards compatible
- Nested macro definitions (a `macro` inside another `macro`) don't always work correctly when invoked from external crates.
- pending improvements in how we encode macro definitions in crate metadata
- There is no way to "escape" hygiene without using a procedural macro.
r? @nrc
This support is needed for bindgen to work well on 32-bit Windows, and
also enables people to begin experimenting with C++ FFI support on that
platform.
Fixes#42044.
Also, add detection to treat such comments as tidy errors.
We also remove the found_lib_feature code because it
was just repeating the found_feature code. Originally it
was intended to allow for gate-test lines for
lib features, but apparently nobody missed it.
Add better error message when == operator is badly used
Part of #40660.
With the following code:
```rust
fn foo<T: PartialEq>(a: &T, b: T) {
a == b;
}
fn main() {
foo(&1, 1);
}
```
It prints:
```
error[E0277]: the trait bound `&T: std::cmp::PartialEq<T>` is not satisfied
--> test.rs:2:5
|
2 | a == b;
| ^^^^^^ can't compare `&T` with `T`
|
= help: the trait `std::cmp::PartialEq<T>` is not implemented for `&T`
= help: consider adding a `where &T: std::cmp::PartialEq<T>` bound
error: aborting due to previous error
```
