Range code and inference errors

[Mathias Lang via Digitalmars-d]

Hi everyone,
I've been doing quite a lot of range-based code lately and I've 
been bugged with an UX problem that's IMHO a real bummer for 
range usage to new users.

Take the example code:
```
import std.algorithm;
void main()
{
     auto foo = [ "foo": "foo", "bar": "bar", "foobar": "foobar" ];
     assert(foo.byKeyValue.all!((kvp) => kvp.Key == kvp.Value));
}
```

Quite straightforward, right ? Some of you might already have 
spotted the error, but here's what DMD think of it:

```
test.d(6): Error: template std.algorithm.searching.all cannot 
deduce function from argument types !((kvp) => kvp.Key == 
kvp.Value)(Result), candidates are:
/dlang/dmd-2.067.0/linux/bin64/../../src/phobos/std/algorithm/searching.d(100):        std.algorithm.searching.all(alias pred = "a")

```

This happens because I got the delegate wrong. To get the right 
error, you have to know errors are gagged and so, let's remove 
the type inference error:

```
assert(foo.byKeyValue.all!((typeof(foo.byKeyValue.front) kvp) => 
kvp.Key == kvp.Value));
```

Which gives a proper error message:

```
test.d(6): Error: no property 'Key' for type 'Pair', did you mean 
'key'?
test.d(6): Error: no property 'Value' for type 'Pair', did you 
mean 'value'?
```

Any change we can fix that ?