Capture parameter on Mutable classes crashes the compiler

[Linyxus]

Compiler version

main

Minimized code

import language.experimental.captureChecking
class Ref extends caps.Mutable
def f1[C1^](a: Ref^{C1}): Unit =
  val t = a

Output

It crashes.

Expectation

It should not crash.

[Linyxus]

Will be fixed by #24295.