The test is conditionally XFAILed for the release configuration only,
but using `expectCrash(executing:)` make it fail even in release mode,
but for a wrong reason (`expectUnreachable()` is unconditional).
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.
This decreases total testing time by over a minute on my old Mac Pro.
It probably has much less effect on systems with fewer cores, but shouldn't
be any worse there.
Swift SVN r22745
To limit user confusion when using conditional expressions of type Bool?, we've decided to remove the BooleanType (aka "LogicValue") conformance from optional types. (If users would like to use an expression of type Bool? as a conditional, they'll need to check against nil.)
Note: This change effectively regresses the "case is" pattern over types, since it currently demands a BooleanType conformance. I've filed rdar://problem/17791533 to track reinstating it if necessary.
Swift SVN r20637
Similar to nil-coalescing operators in other languages, this operator takes an optional on the left and a non-optional expression on the right, and if the optional is nil, evaluates the right side, otherwise returning the value from the optional itself. <rdar://problem/15247356>
Swift SVN r20593
This is motivated by <rdar://problem/17051606>.
This ends up renaming variables as well, which seems right for
consistency since we use "predicate" as variable name.
Swift SVN r19135
