Rule Request: typesafe_shorthand_operator

[SimplyDanny]

The existing shorthand_operator rule causes false positives for operands that don't support the suggested shorthand operator. Examples have been brought up in #3603, #3643 and #4936. The rule doesn't know anything about the operands' types so such mistakes are unavoidable and must be accepted.

A new typesafe version of shorthand_operator could be added, however, that knows depending on the types of the operands if a shorthand operator is supported or not. It can be based on the existing rule with additional type information at hand.

A similar pair of rules is already available with ArrayInitRule and TypesafeArrayInitRule.