[Issue 24654] Parameters in contracts should be `const`

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24654

--- Comment #3 from Nick Treleaven <nick at geany.org> ---
> Of course they convert to const

Sorry, yes. The Issue 24565 problem was calling methods not annotated with
const. So if this was implemented, it should be done in an edition to avoid
breaking working correct code.

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