[Issue 22023] New: adding `return` to escaped argument of a variadic defeats @safe

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22023

          Issue ID: 22023
           Summary: adding `return` to escaped argument of a variadic
                    defeats @safe
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: major
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: iamthewilsonator at hotmail.com

Given 
```
Foo createFoo() @safe {
    return Foo(1, 2, 3);
}

void main() @safe {
    import std.stdio : writeln;
    auto foo = createFoo();
    foreach (f; foo.e) writeln(f, " ");
}
```

Defining Foo as:
```
struct Foo {
    this(int[] e...) @safe {
        this.e = e;
    }
    int[] e;
}
```
correctly errors as "Error: scope variable `e` assigned to `this` with longer
lifetime"
Adding return to the variadic argument 
```
struct Foo {
    this(return int[] e...) @safe {
        this.e = e;
    }
    int[] e;
}
```

Compiles and prints garbage: e.g. 
1 
0 
2003568368

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