Support for more user defined arithmetical operators

[DartBot]

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

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Support for +=, -=, *= and /= on num and made available to be overloaded.

[floitschG]

Removed Type-Defect label.
Added Type-Enhancement, Area-Language labels.

[DartBot]

This comment was originally written by drfibonacci@google.com

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Added Triaged label.

[gbracha]

I'm renaming this issue so it reflects its content more clearly. I think adding more user definable operators is a definite possibility in the future, but I don't think that will include the specific ones listed here. The reason is that they are all derived. If you define what + (or - or * or /) operator you want, the meaning of += is derived from that. We do not want the two to diverge.

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Set owner to @gbracha.
Added Accepted label.
Changed the title to: "Support for more user defined arithmetical operators".

[anders-sandholm]

Added this to the Later milestone.

[kasperl]

Removed this from the Later milestone.
Added Oldschool-Milestone-Later label.

[kasperl]

Removed Oldschool-Milestone-Later label.

[lrhn]

Closed by accident

[munificent]

Like Gilad says, we specifically don't want to allow overriding the self-assignment operators because users could make them diverge from their desugaring, which is almost never a good idea. (Even C#'s use of += for events gets weird at times.)

Since those are the operators this bug originally refers to, I'm going to go ahead and close this out. Arbitrary user-defined custom operators are a different kettle of fish.