[Issue 20876] generated constructor always inout regardless of ability of fields to use inout

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20876

--- Comment #14 from Walter Bright <bugzilla at digitalmars.com> ---
Even smaller test case:

struct S {
    this(ref S) { }
}

struct T {
    S s;
}

void test()
{
    T t;
    T u = t;
}

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