[Issue 20937] New: std.range.array of a lengthless range with indirection is not @safe

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20937

          Issue ID: 20937
           Summary: std.range.array of a lengthless range with indirection
                    is not @safe
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: safe
          Severity: normal
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: pro.mathias.lang at gmail.com

```
import std.algorithm;
import std.array;

struct S
{
    ulong[] values;
}

void main () @safe
{
    immutable arr = [ S([1]), S([2]), S([3]), S([4]), S([42]), S([84]),
S([121]) ];
    auto intermediate = arr.filter!(v => !!(v.values[0] % 2));
    auto result = intermediate.array;
}
```

What I expected: `result` should be of a type that converts to
`immutable(S)[]`.
What I got:
```
foo.d(13): Error: @safe function D main cannot call @system function
std.array.array!(FilterResult!(__lambda1, immutable(S)[])).array
/usr/local/opt/dmd/include/dlang/dmd/std/array.d(102):       
std.array.array!(FilterResult!(__lambda1, immutable(S)[])).array is declared
here
```

--