Question about deprecation process

[Michael V. Franklin]

I've resurrected a PR that fixes an implementation bug.  
https://github.com/dlang/dmd/pull/7332

The existing implementation does not comply with the spec.  The 
PR fixes that, but it may cause breakage, so in the original PR, 
there was a preference to have it go through the deprecation 
process.

The deprecation process documented at 
https://dlang.org/deprecate.html#Imaginary%20and%20complex%20types gives the following procedure (kindof).


Spec - Removal from the Specification
Dep - The compiler warns by default, issues an error with the -de 
switch, and can be silenced with the -d switch
Error - It is an error to use the feature
Gone - The feature is completely gone

While I'm sure there are exceptions, *typically* for how long, or 
how many releases, is the Deprecation warning to remain in place 
before the Error is released?  Also, for how long, or how many 
releases, is the Error to remain in place before the feature is 
removed?  Is that currently documented anywhere?

Thanks,
Mike