[Issue 19885] New: possibility to skip required initialization in constructor using ref parameter

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19885

          Issue ID: 19885
           Summary: possibility to skip required initialization in
                    constructor using ref parameter
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: regression
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: regnellday at protonmail.com

This code compiles (since 2.081.2), but shouldn't:

struct A
{
    @disable this();
    this(int) {}
}

struct B
{
    A a;
    this(int)
    {
        f(a);
    }
}

void f(ref A a) {}

void main()
{
    B b = B(1);
}

The `a` must be constructed in the `B` constructor. But if we pass it somewhere
via ref parameter, compiler ignores `a` and leaves it in default state.

By the way, if we change ref to out, then there is normal `Error: cannot have
out parameter of type A because the default construction is disabled`.

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