For following:

```rust
struct A;
impl A {
    fn test4(&self) {
        let mut _file = File::create("foo.txt")?;
        //~^ ERROR the `?` operator can only be used in a method
    }
```
Suggest:

```rust
impl A {
    fn test4(&self) -> Result<(), Box<dyn std::error::Error>> {
        let mut _file = File::create("foo.txt")?;
        //~^ ERROR the `?` operator can only be used in a method

    Ok(())
    }
}
```

For rust-lang#125997

The documentation incorrectly stated that std::env::var could return
an error for variable names containing '=' or the NUL byte. Copy the
correct documentation from var_os.

var_os was fixed in Commit 8a7a665, Pull Request rust-lang#109894, which
closed Issue rust-lang#109893.

This documentation was incorrectly added in commit f2c0f29, which
replaced a panic in var_os by returning None, but documented the
change as "May error if ...".

Reference the specific error values and link to them.

... by using `std::fs::remove_dir_all`, which handles a bunch of edge
cases including read-only files and symlinks which are extremely tricky
on Windows.

During config parsing, some bootstrap logic (e.g., `download-ci-llvm`) checks certain sources
and acts based on their state. This means that if path is a git submodule, bootstrap needs to
update it before checking its state. Otherwise it may make incorrect assumptions by relying on
outdated sources. To enable submodule updates during config parsing, we need to move the `update_submodule`
function from the `Build` to `Config` instance, so we can access to it during the parsing process.

Signed-off-by: onur-ozkan <work@onurozkan.dev>

Signed-off-by: onur-ozkan <work@onurozkan.dev>

Signed-off-by: onur-ozkan <work@onurozkan.dev>

It's only valid when applied to a type or lifetime parameter
in `Drop` trait implementation.

Suggest adding Result return type for associated method in E0277.

Recommit rust-lang#126515 because I messed up during rebase,

Suggest adding Result return type for associated method in E0277.

For following:

```rust
struct A;
impl A {
    fn test4(&self) {
        let mut _file = File::create("foo.txt")?;
        //~^ ERROR the `?` operator can only be used in a method
    }
```

Suggest:

```rust
impl A {
    fn test4(&self) -> Result<(), Box<dyn std::error::Error>> {
        let mut _file = File::create("foo.txt")?;
        //~^ ERROR the `?` operator can only be used in a method

    Ok(())
    }
}
```

For rust-lang#125997

r? ````@cjgillot````

…rkingjubilee

doc: std::env::var: Returns None for names with '=' or NUL byte

The documentation incorrectly stated that std::env::var could return an error for variable names containing '=' or the NUL byte. Copy the correct documentation from var_os.

var_os was fixed in Commit 8a7a665, Pull Request rust-lang#109894, which closed Issue rust-lang#109893.

This documentation was incorrectly added in commit f2c0f29, which replaced a panic in var_os by returning None, but documented the change as "May error if ...".

Reference the specific error values and link to them.

…links, r=Kobzol

bootstrap: fix clean's remove_dir_all implementation

It turns out bootstrap's `clean.rs`'s hand-rolled `rm_rf` (which probably comes before `std::fs::remove_dir_all` was stable) is very broken on native Windows around both read-only files/directories and especially symbolic links. So instead of rolling our own, just use `std::fs::remove_dir_all`.

This is a blocker for compiletest's own `rm_rf` implementation rust-lang#129155 which happens to be also buggy, which in turn is a blocker for the rmake.rs test port rust-lang#128562 that heavily exercises symlinks (I was reviewing rust-lang#128562 and testing it on native Windows which is how I found out).

I also left a FIXME for `detect_src_and_out` due to a failing assertion on native Windows (opened rust-lang#129188):

```
---- core::config::tests::detect_src_and_out stdout ----
thread 'core::config::tests::detect_src_and_out' panicked at src\core\config\tests.rs:72:13:
assertion `left == right` failed
  left: "E:\\tmp"
 right: "C:\\tmp"
```

Fixes rust-lang#112544 (because now we handle Windows symlinks properly).

try-job: x86_64-msvc
try-job: i686-mingw
try-job: test-various
try-job: armhf-gnu
try-job: aarch64-apple
try-job: aarch64-gnu

…ulacrum

Fix bootstrap test `detect_src_and_out` on Windows

Fixes rust-lang#129188 by making sure it's properly testing the right path for the platform.

…es, r=Mark-Simulacrum

improve submodule updates

During config parsing, some bootstrap logic (e.g., `download-ci-llvm`) checks certain sources (for `download-ci-llvm`, it's `src/llvm-project`) and acts based on their state. This means that if path is a git submodule, bootstrap needs to update it before checking its state. Otherwise it may make incorrect assumptions by relying on outdated sources. To enable submodule updates during config parsing, we need to move the `update_submodule` function from the `Build` to `Config`, so we can access to it during the parsing process.

Closes rust-lang#122787

…piler-errors

Check that `#[may_dangle]` is properly applied

It's only valid when applied to a type or lifetime parameter in `Drop` trait implementation.

Tracking issue: rust-lang#34761
cc rust-lang#34761 (comment)

Typo

Fix a typo in a comment.