complex numeric type (like vec2, vec3) is warned when negate operator overriding

[DartBot]

This issue was originally filed by halak...@gmail.com

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What steps will reproduce the problem?

1. create vec2, vec3, mat4 class.
     class vec2 { num x; num y; vec2(this.x, this.y); }
2. override negate operator
     class vec2 { ... vec2 operator negate() { return new vec2(-x, -y); } }
3. compiler warn "operator 'negate' should return numeric type"

What is the expected output? What do you see instead?
no compiler warning

What version of the product are you using? On what operating system?
Windows7

Please provide any additional information below.

[anders-sandholm]

Assuming it's dart2js and not the VM as the description says compiler...

halakshin, could you provide a full self-contained coherent code sample and attach it?

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Added Area-Dart2JS, NeedsInfo labels.

[DartBot]

This comment was originally written by jjinux...@google.com

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I ran into this too. If you type this into Dart editor:

class Vector {
  Vector operator negate() {
    return new Vector();
  }
}

main() {
}

You'll get this warning:

operator 'negate' should return numeric type

I think you should be able to negate things like vectors.

[DartBot]

This comment was originally written by domi...@google.com

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See also http://github.com/johnmccutchan/DartVectorMath which gets warnings from analyzer on operator negate() on quat, mat* and vec*.

[DartBot]

This comment was originally written by @financecoding

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Looking at the dart spec, the static analyzer should be correct for providing warnings. Why this is a warning is something I might not fully understand.

http://goo.gl/hK8ix
7.1.2 Operators
[...]
It is a static warning if the return type of the user-declared operator []=
is explicitly declared and not void. It is a static warning if the return type
of the user-declared operator equals is explicitly declared and is not bool. It
is a static warning if the return type of the user-declared operator negate is
explicitly declared and not a numerical type.

[DartBot]

This comment was originally written by @financecoding

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Rereading the spec

[...]
Dening a nullary method named negate or a binary method named equals will
have the same effect as dening an operator but is considered bad style, and will
cause a static warning.
[...]

[kasperl]

This sounds like a specification issue to me. We do not "force" other arithmetic operators to return numeric types, so I don't think we should force the unary negate operator to do so. Is this a known issue, Gilad?

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Set owner to @gbracha.
Removed Area-Dart2JS label.
Added Area-Language, Triaged labels.

[gbracha]

Added Done label.