Creating InputRanges from strings, files etc.

[Vinay Sajip]

On Thursday, 8 November 2018 at 14:38:37 UTC, Paul Backus wrote:
> To pass these ranges around using the `InputRange` interface, 
> use `inputRangeObject` to wrap them:
>
>     InputRange!ubyte r3 = inputRangeObject(r1);
>     InputRange!(immutable(ubyte)) r4 = inputRangeObject(r2);

I did a bit more digging, and it seems to work for strings but 
not for files: The program

import std.algorithm.iteration;
import std.format;
import std.range;
import std.stdio;
import std.string;

void somefn(InputRange!(immutable(ubyte)) r) {
     writeln(format!"%s"(r));
}

void main()
{
     auto a = "Hello, world!";
     auto b = inputRangeObject(a.representation);
     somefn(b);
     auto c = stdin.byChunk(1024).joiner;
     auto d = inputRangeObject(c);
     //somefn(d);
}

compiles as given above, but if the somefn(d) line is 
uncommented, I get an error:

function onlineapp.somefn(InputRange!(immutable(ubyte)) r) is not 
callable using argument types (InputRangeObject!(Result))
onlineapp.d(18):        cannot pass argument d of type 
std.range.interfaces.InputRangeObject!(Result) to parameter 
InputRange!(immutable(ubyte)) r

Do I need to do an explicit cast? If so, can someone tell me the 
precise incantation? How come it doesn't figure out that the 
underlying range is a ubyte range, or is it to do with 
immutability, or something else altogether?