Lint idea: unlinked symbol in doc comment

[smoelius]

Consider this program:

/// Calls `bar`.
pub fn foo() {
    bar();
}

fn bar() {}

In the doc comment, bar could be linked:

/// Calls [`bar`].
pub fn foo() {
    bar();
}

fn bar() {}

I'm not sure how difficult this would be to implement. I think Clippy has utilities for parsing doc comments. Perhaps the lint could walk the enclosing module and look for symbols with names that appear in the doc comments.