Can't make inout work.

[Paul Backus]

On Sunday, 17 March 2019 at 10:49:03 UTC, aliak wrote:
> Ah! Thanks! So next problem with that:
>
> import std.stdio;
>
> struct S(T) {
>     T value;
> }
>
> auto make(T)(inout auto ref T val) {
>     return inout(S!T)(val);
> }
>
> void main() {
>     writeln(make("hello") == S!string("hello"));
> }
>
> Error: Error: incompatible types for (make("hello")) == 
> (S("hello")): immutable(S!(char[])) and S!string
>
> I think that's just this bug (which is marked as a diagnostic 
> for some reason): https://issues.dlang.org/show_bug.cgi?id=19126
>
> Thoughts on any workarounds?

For some reason, when you call `make("hello")`, the template 
argument T is being inferred as char[] instead of string. (You 
can see this by putting `pragma(msg, T)` in the body of make.) It 
works if you instantiate make explicitly with 
`make!string("hello")`.

This seems like a bug to me. If you remove inout from the code, T 
is correctly deduced as string.