Rustdoc: Wrong documentation in case of types that only implement Deref, but not DerefMut

[Sawyer47]

Wrong documentation is generated for types that only implement Deref, but not DerefMut. It inherits methods from both Deref and DerefMut.

Steps to reproduce:
cargo new deref-doc-bug

/// lib.rs
pub struct Foo;

impl std::ops::Deref for Foo {
    type Target = [char];
    fn deref(&self) -> &[char] { &[] }
}

cargo doc --open

Generated documentation has methods for both &[char] and &mut [char], for examplefn get_mut.

Version

rustc 1.12.0-nightly (1225e122f 2016-07-30)
rustdoc 1.12.0-nightly (1225e122f 2016-07-30)

[Mark-Simulacrum]

Cannot reproduce, versions below:

cargo:
cargo 0.13.0-nightly (c205132 2016-08-09)

rustc:

rustc 1.12.0-nightly (1deb02ea6 2016-08-12)
binary: rustc
commit-hash: 1deb02ea69a7ca3fd8011a45bb75ff22c3f7579a
commit-date: 2016-08-12
host: x86_64-apple-darwin
release: 1.12.0-nightly

rustdoc:

rustdoc 1.12.0-nightly (1deb02ea6 2016-08-12)
binary: rustdoc
commit-hash: 1deb02ea69a7ca3fd8011a45bb75ff22c3f7579a
commit-date: 2016-08-12
host: x86_64-apple-darwin
release: 1.12.0-nightly

[Sawyer47]

I still reproduce it. Maybe my description was not entirely clear. If a type implements the std::ops::Deref trait then there is an additional section in its documentation page Methods from Deref<Target=...>.
Even though Deref::deref returns an immutable reference, the generated documentation contains all methods, including those that would require DerefMut implementation for the code to compile.

So, considering the example code from my previous message :

    let mut foo = Foo;
    assert_eq!(foo.len(), 0);      // ok
    assert_eq!(foo.get(0), None);  // ok
    // compile error, but generated documentation lists get_mut as an available function
    assert_eq!(foo.get_mut(0), None); 

I quickly grepped the source code and it looks like rustdoc only checks for the implementation of Deref
(link to code).