rust_2021_incompatible_or_patterns misses some patterns that fail in 2021

[ehuss]

I tried this code:

#![warn(rust_2021_incompatible_or_patterns)]

macro_rules! mac {
    (|$a:pat, $b:pat|) => {};
    (|$a:pat|) => {};
}

fn main() {
    mac!(|a|);
}

I expected to see this happen: Suggestions should change all pat matchers to pat_param.

Instead, this happened: The lint misses the first pattern. That is, after the suggestions:

#![warn(rust_2021_incompatible_or_patterns)]

macro_rules! mac {
    (|$a:pat, $b:pat_param|) => {};
    (|$a:pat_param|) => {};
}

fn main() {
    mac!(|a|);
}

But this fails to compile in 2021:

error: expected pattern, found `<eof>`
 --> src/main.rs:9:12
  |
4 |     (|$a:pat, $b:pat_param|) => {};
  |       ------ while parsing argument for this `pat` macro fragment
...
9 |     mac!(|a|);
  |           -^ expected pattern
  |           |
  |           while parsing this or-pattern starting here

Found while trying to migrate stakker 0.2.4.

Meta

rustc --version --verbose:

rustc 1.56.0-nightly (0035d9dce 2021-08-16)
binary: rustc
commit-hash: 0035d9dcecee49d1f7349932bfa52c05a6f83641
commit-date: 2021-08-16
host: x86_64-apple-darwin
release: 1.56.0-nightly
LLVM version: 12.0.1

[m-ou-se]

If it is a single arm, both :pats get correctly replaced by :pat_param:

macro_rules! mac {
    (|$a:pat $(, $b:pat)?|) => {};
}

But we're not doing any analysis across different arms of a macro rules, so this issue is somewhat expected.

The same happens with

macro_rules! mac {
    ($a:expr) => {};
    (...) => {};
}

Where ... is anything that's currently not a valid expression, but might be in the future.

[m-ou-se]

Closing this, as this is not something we will be fixing.