It replaces `DeclAttr::getUnavailable()` and `AvailableAttr::isUnavailable()`
as the designated way to query for the attribute that makes a decl unavailable.
FunctionRefKind was originally designed to represent
the handling needed for argument labels on function
references, in which the unapplied and compound cases
are effectively the same. However it has since been
adopted in a bunch of other places where the
spelling of the function reference is entirely
orthogonal to the application level.
Split out the application level from the
"is compound" bit. Should be NFC. I've left some
FIXMEs for non-NFC changes that I'll address in a
follow-up.
The renamed decl is now stored exclusively in the split request evaluator
storage, which is more efficient since most availability attributes do not
specify a renamed decl.
This type is intended to be used to wrap compiler synthesized nodes
(i.e. variables) to make it easier for diagnostic to diagnose precise
failure locations.
Consider the situation like:
```
protocol P {}
extension Array: P where Element: P {}
func test<T: P>() -> T {
$_a = ...
$_b = ...
return [$_a, $_b]
}
```
This is a common pattern with result builders.
In this case if one of the elements don't conform to `P` the best
user experience would be to attach diagnostic to the element otherwise
the developers would have to figure out where in result expression
the error occured before attempting to fix it.
Attempting to dump opaque decl while type-checking a body of
the declaration it's associated with results in a request
cycle because underlying substitutions request would trigger
type-checking if the body isn't type-checked yet.
Rather than exposing an `addFile` member on
ModuleDecl, have the `create` members take a
lambda that populates the files for the module.
Once module construction has finished, the files
are immutable.
If a generic signature states a requirement `each T: P`, we must wrap the
abstract conformance in a pack conformance first.
We let this slide before, but it's now flagged by SubstitutionMap::verify().
When the conforming type is a class-constrained type parameter or
archetype, we must wrap the concrete superclass conformance in an
inherited conformance. This is now flagged by SubstitutionMap::verify().
We checked the wrong condition when deciding if a conformance should
be substituted or not, so we would leave behind opaque return types
in builtin and inherited conformances. This is now flagged by
SubstitutionMap::verify().
Code review identified some incorrect UNIMPLEMENTED_CLONEs in DeclAttribute (thank you
Hamish and Rintaro). Fix those, and make sure this can't happen again by checking the type
signatures of clone() in every DeclAttribute subclass.
