And provide better semantic background by surrounding 'nil' in ticks when it is referred to as a value
Added missing tests for certain cases involving nil capitalization
Specialize and improve the "downcast only unwraps optionals"
diagnostic to provide specific diagnostics + Fix-Its for the various
casts of forced cast, conditional cast, and "isa" check. Specifically:
* With a forced cast, customize the diagnostic. We still insert the
appropriate number of !'s, but now we remove the 'as! T' (if an
implicit conversion would suffice) or replace the 'as!' with 'as'
(if we still need a bridge)
* With a conditional cast, only emit a diagnostic if we're removing
just one level of optional. In such cases, we either have a no-op
(an implicit conversion would do) or we could just use 'as' to the
optional type, so emit a customized warning to do that. If we are
removing more than one level of optional, don't complain:
conditional casts can remove optionals. Add the appropriate Fix-Its
here.
* With an 'is' expression, only emit a diagnostic if we're removing
just one level of optional. In this case, the 'is' check is
equivalent to '!= nil'. Add a Fix-It for that.
Across the board, reduce the error to a warning. These are
semantically-well-formed casts, it's just that they could be written
better.
Fixes rdar://problem/28856049 and rdar://problem/22275685.
Most tests were using %swift or similar substitutions, which did not
include the target triple and SDK. The driver was defaulting to the
host OS. Thus, we could not run the tests when the standard library was
not built for OS X.
Swift SVN r24504
Previously the "as" keyword could either represent coercion or or forced
downcasting. This change separates the two notions. "as" now only means
type conversion, while the new "as!" operator is used to perform forced
downcasting. If a program uses "as" where "as!" is called for, we emit a
diagnostic and fixit.
Internally, this change removes the UnresolvedCheckedCastExpr class, in
favor of directly instantiating CoerceExpr when parsing the "as"
operator, and ForcedCheckedCastExpr when parsing the "as!" operator.
Swift SVN r24253
