`try_err` replaces a macro invocation with a different macro invocation

[jyn514]

I'm going to stop making MCVEs for these in the interest of time; I'll link the original code so you can replicate.

I tried this code: https://github.com/rust-lang/rust/blob/a6ff925f8b5598a1f6d84964525baa1d4a08fd63/compiler/rustc_middle/src/mir/interpret/mod.rs#L72-L75

#[macro_export]
macro_rules! throw_ub {
    ($($tt:tt)*) => { Err::<!, _>(err_ub!($($tt)*))? };
}

I expected to see this happen: Clippy only changes the relevant parts of the code

Instead, this happened: Clippy turns err_ub into throw_ub (??)

error: recursion limit reached while expanding `throw_ub!`
   --> compiler/rustc_middle/src/mir/interpret/mod.rs:74:34
    |
73  | / macro_rules! throw_ub {
74  | |     ($($tt:tt)*) => { return Err(throw_ub!(InvalidUninitBytes(None)).into()) };
    | |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ in this macro invocation (#2)
75  | | }
    | | -
    | | |
    | |_in this expansion of `throw_ub!` (#1)
    |   in this expansion of `throw_ub!` (#2)
    | 
   ::: compiler/rustc_middle/src/mir/interpret/allocation.rs:298:21
    |
298 |               None => throw_ub!(UnterminatedCString(ptr.erase_tag())),
    |                       ----------------------------------------------- in this macro invocation (#1)
    |
    = help: consider adding a `#![recursion_limit="1024"]` attribute to your crate (`rustc_middle`)

error: aborting due to previous error

Original diagnostics will follow.
warning: returning an `Err(_)` with the `?` operator
   --> compiler/rustc_middle/src/mir/interpret/mod.rs:74:23
    |
73  | / macro_rules! throw_ub {
74  | |     ($($tt:tt)*) => { Err::<!, _>(err_ub!($($tt)*))? };
    | |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `return Err(throw_ub!(UnterminatedCString(ptr.erase_tag())).into())`
75  | | }
    | |_- in this expansion of `throw_ub!`
    | 
   ::: compiler/rustc_middle/src/mir/interpret/allocation.rs:298:21
    |
298 |               None => throw_ub!(UnterminatedCString(ptr.erase_tag())),
    |                       ----------------------------------------------- in this macro invocation
    |
    = note: `#[warn(clippy::try_err)]` on by default
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#try_err

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• cargo clippy -V: clippy 0.0.212 (4760b8f 2020-10-25)

[ThibsG]

This is the same error you reported in #6242, but this time the call site (from which the suggestion is built) is also from a macro.