Non-‘@objc’ ‘dynamic’ has been allowed since Swift 5, but there’s no
reason to tie it to the language mode (Swift >= 5).
Fixes rdar://problem/50348013.
This is weird behavior---there's no 'override' keyword here or
anything! But we rely on it when a convenience initializer written in
Objective-C dispatches to another convenience initializer. Changing
this /will/ break some Apple Objective-C classes that are meant to be
subclassed, unfortunately.
...and collapse StaticVar/ClassVar and StaticLet/ClassLet into
StaticProperty/ClassProperty.
"var" and "let" aren't great nouns to use in diagnostics to begin with,
especially alongside semantic terms like "instance method". Focus on
the type vs. non-type aspect instead with "property", which better
matches how people talk about member vars (and lets) anyway.
@IBInspectable and @GKInspectable both work via the Objective-C
runtime. SE-0160 made them imply @objc, but doing so made it an error
to define an @IBInspectable or @GKInspectable property with a type
that could not be expressed in Objective-C. The attribute is useless,
but this broke Swift 3 code.
So, downgrade the error to a warning in Swift 3 compatibility mode,
with a Fix-It to remove the useless attribute. It remains an error in
Swift 4.
Fixes rdar://problem/31408971.
Introduce flags `-enable-swift3-objc-inference` and
`-disable-swift3-objc-inference` to enable/disable the Swift 3 `@objc`
inference rules. Under `-swift-version 3`, default to the former;
under `-swift-version 4`, default to the latter. For testing purposes,
one can provide either flag in eiher language mode.
