Increments the style generation and returns the new value.
Pre-increment semantics are the contract: the caller keeps the value its own
invocation owns, and later compares it against the counter to detect that a
newer switch has superseded it. Returning the pre-increment value would invert
the guard.
Increments the style generation and returns the new value.
Pre-increment semantics are the contract: the caller keeps the value its own invocation owns, and later compares it against the counter to detect that a newer switch has superseded it. Returning the pre-increment value would invert the guard.