[Issue 10850] Inout substituted incorrectly for delegates/fptrs in inout function signature

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=10850

--- Comment #7 from Sobirari Muhomori <dfj1esp02 at sneakemail.com> ---
Binding inout to the outer function is probably an even easier implementation,
than what I propose. But restricting.

Also:
---
void foo(ref inout(int) x){
    inout(int)* bar(inout(int)*) { return &x; }
    int y;
    bar(&y); // error
}
---
Error: modify inout to mutable is not allowed inside inout function
---
The error message should be probably "cannot implicitly convert expression (&
y) of type int* to inout(int)*" like for any other attempt co convert mutable
to inout.

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