Splat is ignored in symbol mangling, leading to symbol clashes

[teor2345]

I tried this code:

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

fn main() {
    #[rustfmt::skip]
    let _x: fn(#[splat] (i32,)) = None.unwrap();

    let x: fn((i32,)) = None.unwrap();
    x((1,));
}

These directives seem to increase the chance of the error:

//@ incremental
//@ compile-flags: -C opt-level=0

I expected to see this happen:

No symbol clashes, either the symbol data is the same (and therefore merged), or it is different, and mangled differently.

Instead, this happened:

When I rebuild the file multiple times with small changes, I eventually get:

error: symbol `_RNvMNtCsCRATE_HASH_4core6optionINtB2_6OptionFTlEEuE6unwrapCsCRATE_HASH_14splat_mangling` is already defined

Meta

rustc version:

git main commit f46ec5218fe

In #153697, we decided not to include splat in symbol mangling. This is likely the cause of this error.

@rustbot label +C-bug +F-splat +T-compiler

cc @oli-obk

[teor2345]

@rustbot claim