Spurious `map_err_ignore` warning when running `cargo clippy` with that warning allowed

I have code in a crate in a workspace which falls afoul of clippy::map_err_ignore (or clippy::map-err-ignore, I've tried with both names), e.g.

// dummy example, my actual code isn't this stupid
fn main() {
  let _result = std::fs::read_to_string("/etc/hostname").map_err(|_| String::new("can't read"));
}

I run the following cargo clippy command:

cargo clippy --workspace --all-targets -- \
		-D warnings \
		-D clippy::pedantic \
		-A clippy::map_err_ignore \
		-A clippy::cast_precision_loss \
		-A clippy::cast_possible_truncation \
		-A clippy::cast_possible_wrap \
		-A clippy::cast_sign_loss \
		-A clippy::must_use_candidate \
		-A clippy::missing_errors_doc \
		-A clippy::if_not_else \
		-A clippy::enum_glob_use

As you can see, I deny any warning or pedantic lint, but specifically allow some choices (including clippy::map_err_ignore, also tried with hyphens rather than underscores). This works fine, except for the map_err_ignore lint. In this case the cargo clippy command emits warnings like the following

warning: `map_err(|_|...` ignores the original error
   --> /workspaces/amoeba/software/vehicle/data/workspace/crypt/src/lib.rs:109:63
    |
2 |      let _result = std::fs::read_to_string("/etc/hostname").map_err(|_| String::new("can't read"));
    |                                                                   ^^^
    |
    = note: `-W clippy::map-err-ignore` implied by `-W clippy::pedantic`
    = help: Consider wrapping the error in an enum variant
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#map_err_ignore

It seems like this is neither following the -D clippy::pedantic flag, nor the -A clippy::map_err_ignore flag, but has somehow inferred -W clippy::map-err-ignore via -W clippy::pedantic, neither of which were specified.

This behaviour does not show up for any of the other lints I specified.

I'm a bit confused about this. Seems most likely that I've made a stupid mistake somewhere, but if so I'm completely blind to it.

Meta

• cargo clippy -V: clippy 0.0.212 (7eac88a 2020-11-16)
• rustc -Vv:

  rustc 1.48.0 (7eac88abb 2020-11-16)
  binary: rustc
  commit-hash: 7eac88abb2e57e752f3302f02be5f3ce3d7adfb4
  commit-date: 2020-11-16
  host: x86_64-unknown-linux-gnu
  release: 1.48.0
  LLVM version: 11.0
  

Start by reproducing the reported cargo clippy --workspace --all-targets invocation with the pedantic, map_err_ignore, and related lint flags using the example in the issue. Trace how lint names and group levels are processed; done means allowing clippy::map_err_ignore suppresses its warning without changing the behavior of the other specified lint levels.