Error messages for wrong number of arguments are confusing

[DartBot]

This issue was originally filed by [email protected]

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This is clearly not a bug in the VM - but as a user it is a persistent source of confusion and I think that fixing this would help usability considerably.

These error messages are different for method calls, constructor calls and super constructor calls.

Here's a test program:
main() {
  C o = new C(2);
  o.m(1);
}

class Base {
  Base();
}

class C extends Base {
  C(var x): super(x); // call super construtor with wrong arg count

  m(var x) => null;
}

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As written, this produces the most confusing of the messages:
$ ../xcodebuild/Release_ia32/dart t.dart
'/Users/jimhug/dartfrog/dart/frog/t.dart': Error: line 16 pos 13: super class constructor 'Base.' not found
  C(var x): super(x);
            ^

If that bug is fixed, but the original call to the constructor is changed to "C o = new C();" then the new message is:
$ ../xcodebuild/Release_ia32/dart t.dart
'/Users/jimhug/dartfrog/dart/frog/t.dart': Error: line 2 pos 9: invalid arguments passed to constructor 'C' for class 'C'
  C o = new C();
        ^
This is the most useful of the messages - but the notion of "invalid arguments" is not clear. It would be very helpful if it specified an incorrect argument count and ideally something of the form, expected 1 argument but found 0.

If that bug is fixed, but the call to m is changed to "o.m()", then the new message is:
$ ../xcodebuild/Release_ia32/dart t.dart
Unhandled exception:
NoSuchMethodException - receiver: 'Instance of 'C'' function name: 'm' arguments: []]
 0. Function: 'Object.noSuchMethod' url: 'bootstrap' line:623 col:3
 1. Function: '::main' url: '/Users/jimhug/dartfrog/dart/frog/t.dart' line:3 col:6

I see how this one is the most difficult to change given the dart spec for NoSuchMethod handling. However, I find this surprising and confusing because it feels to me like there is a method 'm' defined on 'C' - however that method is simply not capable of responding to a message with zero arguments. Again, a message that specified incorrect argument count would be helpful and one that specified "expected 1 argument but found 0" would be most helpful.

[ghost]

Set owner to @sgmitrovic.
Added Accepted label.

[ghost]

NoSuchMethodException is now reporting a method with the same name but different arguments.

[DartBot]

This comment was originally written by [email protected]

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Can I take this one?

[DartBot]

This comment was originally written by [email protected]

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Actually, I have already started implementing the changes, just wanted to see if anyone had any objections to that.

[iposva-google]

Jean-Rémi, no problem if you want to take a crack at it. There were quite a few changes recently about static warnings versus runtime errors, not sure if this particular message is impacted though. If it is please make sure that your implementation matches that.

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cc @gbracha.

[DartBot]

This comment was originally written by [email protected]

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Just want to post an update. I have been procrastinating to get this change made. My summer internship is draining me of my programming energy.

I finally got down to spending a few hours on this toonight and I "fixed" the first case

It now produces the following error message:

[default@jr Debug_ia32]$ ./dart test.dart
'file:///home/default/Google/dart-repo/dart/runtime/out/Debug_ia32/test.dart': Error: line 11 pos 13: expected 0 argument(s) but found 1
  C(var x): super(x); // call super construtor with wrong arg count
            ^

[ghost]

This looks good enough for me.

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Added Fixed label.

[DartBot]

This comment was originally written by [email protected]

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Just to clarify. Since I still haven't taken the time to adress all three sub-issues, I did not yet go through the process of creating a pull request or whichever other way external developers may offer patches.

I am not 100% sure what "this" refers too, just wanted to try and makes things as clear as possible.

[ghost]

case 1:
'file:///sources/chinstrap/dart/Test.dart': Error: line 11 pos 13: invalid arguments passed to super class constructor 'Base.': 1 passed, 0 expected

case 2:
'file:///sources/chinstrap/dart/Test.dart': Error: line 2 pos 14: invalid arguments passed to constructor 'C' for class 'C': 0 passed, 1 expected

case 3:
NoSuchMethod printing is tracked by issue #546.

[DartBot]

This comment was originally written by [email protected]

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It looks like the updated check can behave incorrectly if a mixin presents: https://code.google.com/p/dart/issues/detail?id=9339