Allow required parameters to be named

[DartBot]

This issue was originally filed by sammcca...@google.com

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I'd like to be able to optionally name required parameters at the callsite. (I'd still have to get the position right).

So with
void move(int x, int y);

these are equivalent:
move(x:4, y:2);
move(4, 2);
move(4, y:2);

and these are errors
move(x:4);
move(y:4, x:2);

The main reasons are consistency, readability, and safety.
  * optional parameters names are part of the API, but required parameters are not.
  * optional parameters can be named to increase readability, but required parameters cannot:
    Car(wheels, seats, [doors=4]);
    var sportsCar = new Car(4, 4, 2); // Hard to read
    var van = new Car(4, 8, doors: 3); // Better, but weird
    var truck = new Car(wheels:12, seats:2, doors: 2); // Clearest
  * naming required parameters gives the runtime more information to warn about errors. e.g. accidentally switching the parameter order above will silently do the wrong thing, but if I named the parameters then the compiler would catch the error.

[madsager]

Added Area-Language, Triaged labels.

[peter-ahe-google]

See also: https://groups.google.com/a/dartlang.org/d/topic/misc/XNVE7dY-MBM/discussion

[gbracha]

Set owner to @gbracha.
Removed Type-Defect label.
Added Type-Enhancement, Accepted labels.

[gbracha]

We are looking at separating optional parameters from named parameters, but a bit differently. I hope to have a proposal in th enot-too-distant future.

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Added WontFix label.

[DartBot]

This comment was originally written by colm...@gmail.com

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I know this issue is WontFix but any update on the mentioned proposal to separate optional and named parameters?

[DartBot]

This comment was originally written by dnlj...@gmail.com

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It was in milestone 1, see http://www.dartlang.org/articles/m1-language-changes/#named-optional-params-and-positional-optional-params-are-specified-differently

[DartBot]

This comment was originally written by colms...@gmail.com

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"Named optional params and positional optional params"
but not
"Named required params"
if I understand it properly.

[DartBot]

This comment was originally written by colms...@gmail.com

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Oh, sorry. You were referring to the location of the proposal. My mistake. Thanks for that.