redundant_pattern_match does not trigger on matches! macro

[disco07]

Summary

Uses of matches macro with Result or Option in first argument and in the second argument is just here to check if the first argument is is_ok() or is_some(), do not lint. When I make cargo expand on this:

matches!(Ok::<i32, i32>(10), Ok(_));

I have:

match Ok::<i32, i32>(10) {
        Ok(_) => true,
        _ => false,
    };

Lint Name

redundant_pattern_match

Reproducer

I tried this code:

matches!(Ok::<i32, i32>(10), Ok(_));

I expected to see this happen:

Ok::<i32, i32>(10).is_ok()

Instead, this happened:

matches!(Ok::<i32, i32>(10), Ok(_));

Version

rustc 1.71.0-nightly (521f4dae1 2023-05-19)
binary: rustc
commit-hash: 521f4dae1bdf7fe9cf9436ecef9ee7c7442708bf
commit-date: 2023-05-19
host: x86_64-unknown-linux-gnu
release: 1.71.0-nightly
LLVM version: 16.0.4

[disco07]

@flip1995 I want to work on this, have you some ideas (suggestions) to give me please to resolve this?

[flip1995]

This is a bit complicated. The macro expands to a match expression. The redundant_pattern_match lint i probably has a span.from_expansion condition in it, that prevents it from triggering inside of (external) macros. We could loosen that restriction, by checking the expn_data if the expansion (directly) comes from the matches! macro. I think we have a utility function called is_expn_of of something similar for this.

I haven't looked into the code of this lint for quite some time. Let me know, if this explanation already helps you get started, or if you want some more detailed explanation. I'm happy to do that, if necessary :)

[disco07]

@flip1995 Thanks I will explore this path

[disco07]

@rustbot claim