non-lambda overloads for lambda-only things

[Ali Çehreli]

On 4/15/21 3:02 PM, Steven Schveighoffer wrote:
 > Have you ever written something like:
 >
 > auto str = "hello".map(r => r.toUpper).array;

 > To instead get a better error message:
 >
 > Error: static assert:  "You didn't mean to do this. Make your lambda a
 > template parameter"
 >
 >   Is this worth adding to Phobos?
 >
 > -Steve

YES! :)

Coincidentally, I have wasted considerable amount of time just now with 
the following error message:

import std.format;
import std.algorithm;

void main() {
   auto content = q"EOS
1 first line
2 second line
EOS";

   foreach (line; content) {
     int i;
     string s;
     line.formattedRead!"%s %s"(i, s);
   }
}

The first line of the 78-line error message is this:

/usr/include/dmd/phobos/std/format.d(1492): Error: template 
`std.range.primitives.empty` cannot deduce function from argument types 
`!()(immutable(char))`, candidates are:

but the line in format.d, which my editor was showing me was this:

     assert(!r.empty, "Required at least one more input");

I admit that my brain was reading the error message on the source code 
instead of the actual error message and I was scratching my head, trying 
to understand what "one more input" meant.

The programmer's error was something completely different: 'content' is 
not an iterable thing; it's a string. Argh! So, one solution is to 
iterate over content.splitter('\n') in the loop.

Ali