I/O module: deprecate I/O operator <~>

[mppf]

• The <~> operator exists today for I/O
• Like ‘readwrite’, it is designed to support one set of code for both reading and writing
• It also supports chained I/O e.g.

  mychannel <~> myint <~> " " <~> myrecord;

• Has not stood the test of time in Chapel due to ‘read’ and ‘write’ being varargs
  • In practice <~> is almost exclusively used in readThis / writeThis / readWriteThis
    • Due to historical differences in how errors were handled between <~> and channel.write
  • Instead of the above chained example one can write

    mychannel.write(myint, " ", myrecord);

  • Chapel programmers seem to use this form instead (including myself)

Proposal:

• Deprecate the <~> I/O operator
• Leave it available in the parser as an operator available for custom use

[bradcray]

I think if we deprecated it, I'd probably also remove it from the parser as soon as I could b/c it seems arbitrary to support this one operator in case someone needs it rather than defining a bunch of symbolic combinations someone might want, or to introduce the idea of a more general operator identifier.

[benharsh]

My PR #20467 deprecated the <~> operator in the IO module, and deprecated the operator in general. I believe we decided this was the right approach elsewhere/offline, but I wanted to check in on this issue before closing.

Does anyone involved here feel that the general-purpose <~> operator is worth preserving? If so I can remove the current compiler deprecation warning fairly easily.

[bradcray]

Does anyone involved here feel that the general-purpose <~> operator is worth preserving?

Not I.

[benharsh]

In that case I'm closing this issue. I believe the only remaining work here is to remove the <~> operator from the compiler, modules, and tests in its entirety. This should be a fairly small task that I can do post-release.