Mark Lacey 8b55a0f61b SE-0054: Rework diagnostics for IUOs and revise Swift 3 /4 semantics. ...

For Swift 3 / 4:

Deprecate the spelling "ImplicitlyUnwrappedOptional", emitting a warning
and suggesting "!" in places where they are allowed according to
SE-0054.

In places where SE-0054 disallowed IUOs but we continued to accept them
in previous compilers, emit a warning suggesting "Optional" or "?"  as
an alternative depending on context and treat the IUO as an Optional,
noting this in the diagnostic.

For Swift 5:

Treat "ImplicitlyUnwrappedOptional" as an error, suggesting
"!" in places where they are allowed by SE-0054.

In places where SE-0054 disallowed IUOs, emit an error suggestion
"Optional" or "?" as an alternative depending on context.

2017-11-18 11:41:53 +09:00

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