Broken LLVM function when pushing dyn* item to Vec.

[mejrs]

Playground

Code

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

use core::fmt::Debug;

fn main() {
    let mut v = vec![];
    let i = 42_u8 as dyn* Debug;
    v.push(i);
}

Result:

Call parameter type does not match function signature!
i8 42
 i64  invoke void @"_ZN5alloc3vec16Vec$LT$T$C$A$GT$4push17h57979dab0e1643c2E"(ptr align 8 %3, i8 42, ptr align 8 @6)
          to label %14 unwind label %8, !dbg !2675
in function _ZN10playground4main17h68903ee09fbec9bcE
LLVM ERROR: Broken function found, compilation aborted!

Meta

1.66.0-nightly (2022-09-21 9062b780b32d2eab060b)

@rustbot label: +F-dyn_star +requires-nightly +A-LLVM

[matthiaskrgr]

Miri actually reports this as a bug :)

error: Undefined Behavior: scalar size mismatch: expected 8 bytes but got 1 bytes instead
 --> src/main.rs:8:13
  |
8 |     let i = 42_u8 as dyn* Debug;
  |             ^^^^^^^^^^^^^^^^^^^ scalar size mismatch: expected 8 bytes but got 1 bytes instead
  |
  = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
  = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
  = note: BACKTRACE:
  = note: inside `main` at src/main.rs:8:13

[compiler-errors]

FYI: We currently have 0 checks that dyn* actually fit their size requirement currently.