Somewhat related to
https://github.com/D-Programming-Language/phobos/pull/2024
I wonder about the soundness of `map` in
```D
import std.algorithm, std.range, std.stdio;
void main(string[] args)
{
long[] arr;
const n = 3;
iota(n).map!(a => arr ~= a);
writeln(arr);
writeln(iota(n).map!(a => arr ~= a));
writeln(arr);
}
```
that prints
```D
[]
[[0], [0, 1], [0, 1, 2]]
[0, 1, 2]
```
Shouldn't a warning at least be issued for return-ignoring calls
to map with mutating lambdas? Has there been any discussions on
making map require pure functions now that we have each? I guess
a new function, say `mapPure`, may be neccessary as adding such a
restriction to the lambda will break too much code right?
