Embedded Swift doesn't have protocol conformance metadata, so it cannot
handle dynamic casts to existentials (nor should it).
Another part of rdar://119383905.
The existing SIL-level diagnostic for this check only triggers when
the type is actually used, while the type-checker version is more
eager. Stage in the stricter check as a warning and we'll clamp down
on things later.
Generic methods declared in protocols (and extensions thereof) cannot
be used on existential values, because there is no way to specialize
them for all potential types. Diagnose such cases in Embedded Swift
mode and via `-Wwarning EmbeddedRestrictions`.
This adds a bunch more warnings to the standard library that we'll
need to clean up, probably by `#if`'ing more code out.
Part of rdar://119383905.
Move the diagnostic about non-final generic methods in classes up to
the type checker, so that it is available to `-Wwarning
EmbeddedRestrictions` and earlier in the pipeline. The SIL version of
this is still available as a backstop.
Yet another part of rdar://133874555.
These restrictions will generally manifest as failures of various forms
later in the compiler process. Enable the diagnostics to give earlier
feedback to help stay within the bounds of Embedded Swift.
Fixes rdar://121205043.
When emitting diagnostics for the Embedded Swift restrictions outside
of Embedded Swift mode, consider `#if $Embedded` and `#if
hasFeature(Embedded)` configurations. If the code where we would emit
the diagnostic would be disabled in Embedded Swift by one of those
checks, don't emit the diagnostic. This helps code that can compile
either with Embedded or regular Swift stay within the restrictions on
Embedded Swift.
Untyped throws depends on existentials (`any Error`), and is therefore
not available in Embedded Swift. Introduce a diagnostic that diagnoses
any use of untyped throws, suggesting that one use typed throws
instead.
Make this an opt-in diagnostic enabled with `-Wwarning
EmbeddedRestrictions`, whether in Embedded Swift or not, using the
"default ignore" flag on these new warnings. Document this new
diagnostic group, and put the existing Embedded Swift error about
weak/unowned references in it as well.
Part of the general push to have the type checker identify code that
will not compile as Embedded Swift earlier, rdar://133874555.
