DIP 1030--Named Arguments--Community Review Round 1 Discussion

[Adam D. Ruppe]

On Thursday, 13 February 2020 at 01:37:58 UTC, Walter Bright 
wrote:
>     static if (condition) pragma(msg, "Look, Ma!");

In this context, the condition there would be someone using the 
parameter names. That's impossible to find in static if.

> Note that the compiler already uses a spell checker to look for 
> close symbol matches.

A spell checker wouldn't necessarily catch a name change like 
this since the distance between old and new name may be 
significant. (e.g. ms to milliseconds has an edit distance of ... 
what, 11?)

The current spell checker doesn't do it:

int milliseconds() { return 0; }

void main() {
         int a = ms();
}

// wer.d(4): Error: undefined identifier ms
// note no suggestion given


But since the number of parameters is so limited, process of 
elimination means even with a very large edit distance, it is 
still probable that you meant one of the few missing parameters. 
Like dmd will right now suggest:

wer.d(4): Error: function wer.milliseconds(int ms) is not 
callable using argument types ()
wer.d(4):        missing argument for parameter #1: int ms


So a natural extension of this could be

     given named argument `milliseconds` does not match any 
parameter
     missing argument for parameter #1: int ms


And just those two messages next to each other, spell check or 
no, would probably clue the user in. I doubt this will even need 
additional code, but nevertheless, given the importance of good 
error messages to user productivity, I think all DIPs ought to 
have a section on diagnostics and any implementation should 
ensure it is addressed one way or another.