Bug 11481 – Clearly note all explicit casts are forwarded to `alias this` if there is no `opCast`

People tend to think explicit cast behaves as no-op if there is an implicit one. Documentation must clearly note it's wrong and `opCast` is tried to be called. Also a list of operations rewritten as explicit cast like `if(someStruct)` must be provided as people tend to forget invisible explicit casts exist. Appendix: * Filed invalid bugs because of this: Issue 3537, Issue 6777, Issue 7985, Issue 9151. * Lockup mechanics explanation by Kenji Hara: Comment 2 of Issue 11161.

(In reply to comment #0) > People tend to think explicit cast behaves as no-op if there is an implicit > one. Documentation must clearly note it's wrong and `opCast` is tried to be > called. > > Also a list of operations rewritten as explicit cast like `if(someStruct)` must > be provided as people tend to forget invisible explicit casts exist. > > Appendix: > * Filed invalid bugs because of this: Issue 3537, Issue 6777, Issue 7985, Issue > 9151. Issue 9151 is the only instance of this. Simply adding an alias this must not result in hijacking, so the current behaviour is unacceptable for the other issues. > * Lockup mechanics explanation by Kenji Hara: Comment 2 of Issue 11161. How exactly DMD derives unreasonable behaviour is not relevant for answering the question whether the behaviour is reasonable.