`useless_asref` lint produces incorrect fix suggestion that causes type error with `Cow::Borrowed`

### Summary

When running `cargo +nightly clippy --fix`, the `useless_asref` lint incorrectly suggests removing `.as_ref()` from code that maps `&&str` to `Cow::Borrowed(&str)`, resulting in a type error after the automatic fix is applied.

### Lint Name

clippy::useless_asref

### Reproducer

### Clone and checkout the repository

```sh
git clone git@github.com:carthage-software/mago.git
cd mago/mago
git checkout 0de9868  # commit where the issue occurs
```

### Run clippy with automatic fixes

```sh
cargo +nightly clippy --workspace --all-targets --all-features --fix --allow-dirty --allow-staged
```

The command will fail with the following error after attempting to apply the automatic fix:

```
warning: failed to automatically apply fixes suggested by rustc to crate `mago_orchestrator`

after fixes were automatically applied the compiler reported errors within these files:

  * crates/orchestrator/src/lib.rs

This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report!

The following errors were reported:
error[E0277]: a value of type `std::vec::Vec<std::borrow::Cow<'_, str>>` cannot be built from an iterator over elements of type `std::borrow::Cow<'_, &str>`
    --> crates/orchestrator/src/lib.rs:186:81
     |
 186 |             extensions: self.config.extensions.iter().map(|s| Cow::Borrowed(s)).collect(),
     |                                                                                 ^^^^^^^ value of type `std::vec::Vec<std::borrow::Cow<'_, str>>` cannot be built from `std::iter::Iterator<Item=std::borrow::Cow<'_, &str>>`
     |
     = help: for that trait implementation, expected `str`, found `&str`
```

### Original Warning

Before the fix is applied, clippy shows:

```
warning: this call to `as_ref` does nothing
   --> crates/orchestrator/src/lib.rs:186:77
    |
186 |             extensions: self.config.extensions.iter().map(|s| Cow::Borrowed(s.as_ref())).collect(),
    |                                                                             ^^^^^^^^^^ help: try: `s`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_asref
```

## Expected Behavior

Either:
1. The lint should suggest replacing `s.as_ref()` with `*s` (the correct fix), or
2. The lint should not trigger on this code (since `.as_ref()` serves a purpose)

## Actual Behavior

The lint triggers and suggests removing `.as_ref()` entirely, then applies the fix automatically when using `--fix`, causing the code to fail compilation.

## Correct Fix

The correct fix is to replace `s.as_ref()` with `*s`:

```rust
// Before (triggers clippy warning)
extensions: self.config.extensions.iter().map(|s| Cow::Borrowed(s.as_ref())).collect(),

// Clippy's suggested fix (causes compilation error)
extensions: self.config.extensions.iter().map(|s| Cow::Borrowed(s)).collect(),

// Correct fix (compiles and satisfies clippy)
extensions: self.config.extensions.iter().map(|s| Cow::Borrowed(*s)).collect(),
```

## Full Output

```
    Checking mago-orchestrator v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/orchestrator)
    Checking mago-guard v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/guard)
    Checking mago-linter v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/linter)
    Checking mago-formatter v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/formatter)
    Checking mago-analyzer v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/analyzer)
warning: failed to automatically apply fixes suggested by rustc to crate `mago_orchestrator`

after fixes were automatically applied the compiler reported errors within these files:

  * crates/orchestrator/src/lib.rs

This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust-clippy/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag

The following errors were reported:
error[E0277]: a value of type `std::vec::Vec<std::borrow::Cow<'_, str>>` cannot be built from an iterator over elements of type `std::borrow::Cow<'_, &str>`
    --> crates/orchestrator/src/lib.rs:186:81
     |
 186 |             extensions: self.config.extensions.iter().map(|s| Cow::Borrowed(s)).collect(),
     |                                                                                 ^^^^^^^ value of type `std::vec::Vec<std::borrow::Cow<'_, str>>` cannot be built from `std::iter::Iterator<Item=std::borrow::Cow<'_, &str>>`
     |
help: the trait `FromIterator<std::borrow::Cow<'_, &_>>` is not implemented for `std::vec::Vec<std::borrow::Cow<'_, str>>`
      but trait `FromIterator<std::borrow::Cow<'_, _>>` is implemented for it
    --> /Users/azjezz/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/alloc/src/vec/mod.rs:3670:1
     |
3670 | impl<T> FromIterator<T> for Vec<T> {
     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     = help: for that trait implementation, expected `str`, found `&str`
note: the method call chain might not have had the expected associated types
    --> crates/orchestrator/src/lib.rs:186:55
     |
 186 |             extensions: self.config.extensions.iter().map(|s| Cow::Borrowed(s)).collect(),
     |                         ---------------------- ------ ^^^^^^^^^^^^^^^^^^^^^^^^^ `Iterator::Item` changed to `Cow<'_, &str>` here
     |                         |                      |
     |                         |                      `Iterator::Item` is `&&str` here
     |                         this expression has type `Vec<&str>`
note: required by a bound in `std::iter::Iterator::collect`
    --> /Users/azjezz/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/traits/iterator.rs:2015:19
     |
2015 |     fn collect<B: FromIterator<Self::Item>>(self) -> B
     |                   ^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Iterator::collect`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0277`.
Original diagnostics will follow.

warning: this call to `as_ref` does nothing
   --> crates/orchestrator/src/lib.rs:186:77
    |
186 |             extensions: self.config.extensions.iter().map(|s| Cow::Borrowed(s.as_ref())).collect(),
    |                                                                             ^^^^^^^^^^ help: try: `s`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_asref
    = note: `#[warn(clippy::useless_asref)]` on by default

warning: `mago-orchestrator` (lib) generated 1 warning (run `cargo clippy --fix --lib -p mago-orchestrator` to apply 1 suggestion)
    Checking mago v1.0.0-rc.2 (/Users/azjezz/mago/mago)
    Checking mago-wasm v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/wasm)
warning: failed to automatically apply fixes suggested by rustc to crate `mago_orchestrator`

after fixes were automatically applied the compiler reported errors within these files:

  * crates/orchestrator/src/lib.rs

This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust-clippy/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag

The following errors were reported:
error[E0277]: a value of type `std::vec::Vec<std::borrow::Cow<'_, str>>` cannot be built from an iterator over elements of type `std::borrow::Cow<'_, &str>`
    --> crates/orchestrator/src/lib.rs:186:81
     |
 186 |             extensions: self.config.extensions.iter().map(|s| Cow::Borrowed(s)).collect(),
     |                                                                                 ^^^^^^^ value of type `std::vec::Vec<std::borrow::Cow<'_, str>>` cannot be built from `std::iter::Iterator<Item=std::borrow::Cow<'_, &str>>`
     |
help: the trait `FromIterator<std::borrow::Cow<'_, &_>>` is not implemented for `std::vec::Vec<std::borrow::Cow<'_, str>>`
      but trait `FromIterator<std::borrow::Cow<'_, _>>` is implemented for it
    --> /Users/azjezz/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/alloc/src/vec/mod.rs:3670:1
     |
3670 | impl<T> FromIterator<T> for Vec<T> {
     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     = help: for that trait implementation, expected `str`, found `&str`
note: the method call chain might not have had the expected associated types
    --> crates/orchestrator/src/lib.rs:186:55
     |
 186 |             extensions: self.config.extensions.iter().map(|s| Cow::Borrowed(s)).collect(),
     |                         ---------------------- ------ ^^^^^^^^^^^^^^^^^^^^^^^^^ `Iterator::Item` changed to `Cow<'_, &str>` here
     |                         |                      |
     |                         |                      `Iterator::Item` is `&&str` here
     |                         this expression has type `Vec<&str>`
note: required by a bound in `std::iter::Iterator::collect`
    --> /Users/azjezz/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/traits/iterator.rs:2015:19
     |
2015 |     fn collect<B: FromIterator<Self::Item>>(self) -> B
     |                   ^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Iterator::collect`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0277`.
Original diagnostics will follow.

warning: `mago-orchestrator` (lib test) generated 1 warning (1 duplicate)
    Checking mago-prelude v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/prelude)
    Checking mago-casing v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/casing)
    Checking mago-algebra v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/algebra)
    Checking mago-fingerprint v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/fingerprint)
    Checking mago-codex v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/codex)
    Checking mago-semantics v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/semantics)
    Checking mago-atom v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/atom)
    Checking mago-syntax v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/syntax)
    Checking mago-names v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/names)
    Checking mago-docblock v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/docblock)
    Checking mago-fixer v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/fixer)
    Checking mago-collector v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/collector)
    Checking mago-type-syntax v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/type-syntax)
    Checking mago-reporting v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/reporting)
    Checking mago-syntax-core v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/syntax-core)
    Checking mago-span v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/span)
    Checking mago-database v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/database)
    Checking mago-php-version v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/php-version)
    Checking mago-composer v1.0.0-rc.2 (/Users/azjezz/mago/mago/crates/composer)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 54.20s
```

### Version

```text
rustc +nightly -vV
rustc 1.93.0-nightly (25d319a0f 2025-11-11)
binary: rustc
commit-hash: 25d319a0f656ee8faa7a534da299e76e96068a40
commit-date: 2025-11-11
host: aarch64-apple-darwin
release: 1.93.0-nightly
LLVM version: 21.1.5
```

### Additional Labels

@rustbot label +C-bug +I-false-positive +I-suggestion-causes-error

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`useless_asref` lint produces incorrect fix suggestion that causes type error with `Cow::Borrowed` #16098

Summary

Lint Name

Reproducer

Clone and checkout the repository

Run clippy with automatic fixes

Original Warning

Expected Behavior

Actual Behavior

Correct Fix

Full Output

Version

Additional Labels

Metadata

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useless_asref lint produces incorrect fix suggestion that causes type error with Cow::Borrowed #16098

Description

Summary

Lint Name

Reproducer

Clone and checkout the repository

Run clippy with automatic fixes

Original Warning

Expected Behavior

Actual Behavior

Correct Fix

Full Output

Version

Additional Labels

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions

`useless_asref` lint produces incorrect fix suggestion that causes type error with `Cow::Borrowed` #16098