dead_code lint triggers even though function is used in const pattern

[camelid]

This should compile without warnings (playground):

#![allow(incomplete_features)]
#![feature(inline_const)]

const fn one() -> i32 {
    1
}

fn main() {
    match 1 {
        const { one() } => {}
        _ => {}
    }
}

Yet it warns:

   Compiling playground v0.0.1 (/playground)
warning: function is never used: `one`
 --> src/main.rs:4:10
  |
4 | const fn one() -> i32 {
  |          ^^^
  |
  = note: `#[warn(dead_code)]` on by default

warning: 1 warning emitted

    Finished dev [unoptimized + debuginfo] target(s) in 0.80s
     Running `target/debug/playground`

[camelid]

Note that this only occurs in const patterns. This produces no warnings (playground):

#![allow(incomplete_features)]
#![feature(inline_const)]

const fn one() -> i32 {
    1
}

fn main() {
    match const { one() } {
        1 => {}
        _ => {}
    }
}

Output:

   Compiling playground v0.0.1 (/playground)
    Finished dev [unoptimized + debuginfo] target(s) in 1.06s
     Running `target/debug/playground`

[camelid]

Cc @spastorino – this only occurs with inline const expressions; no warning is triggered with const items.

[nbdd0121]

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