Funny help message "help: consider adding a leading b: bstringify!(foo)"

[glandium]

Reduced testcase:

fn foo() -> bool {
    b"".starts_with(stringify!(foo))
}

Compiler output:

error[E0308]: mismatched types
 --> src/main.rs:2:21
  |
2 |     b"".starts_with(stringify!(foo))
  |                     ^^^^^^^^^^^^^^^
  |                     |
  |                     expected slice, found str
  |                     help: consider adding a leading `b`: `bstringify!(foo)`
  |
  = note: expected type `&[u8]`
             found type `&'static str`

[zackmdavis]

(duplicate of #48835 and #48364, I think)

[kennytm]

Closing as duplicate of #48835. Thanks for the bug report anyway!