Commit to a command line option spelling so that build systems can
start testing it. I deliberately picked one of the longer names we
were considering because we can always decide to add a shorter alias,
but can't decide a shorter name was too generic.
Like the other supplementary output flags,
-emit-parseable-module-interface-path will emit a .swiftinterface file
to a particular path, while -emit-parseable-module-interface will put
it next to the main output (the one specified with -o).
rdar://problem/43776945
We already have something called "module interfaces" -- it's the
generated interface view that you can see in Xcode, the interface
that's meant for developers using a library. Of course, that's also a
textual format. To reduce confusion, rename the new module stability
feature to "parseable [module] interfaces".
Textual module interfaces don't actually depend on SILGen, so we
shouldn't need to run SILGen (or serialize an entire binary module) if
we're just trying to emit a textual interface. On the other hand, if
we /are/ going to run SILGen and then SIL diagnostics, we shouldn't
delay those diagnostics by spending time emitting a textual interface,
or for that matter a TBD file.
Using this, update all the ModuleInterface tests that use
`-emit-module -o /dev/null` to use `-typecheck` instead, except for
those using `-merge-modules`.
...but don't hook it up to anything yet.
This is the very very start of the module stability / textual
interfaces feature described at
https://forums.swift.org/t/plan-for-module-stability/14551/
For now I've just made it a frontend option (not a driver option),
which is good enough for testing.
This dates back to the early days when the Driver was still being
brought up, but there's no reason to put them together now.
Reorganization and elimination of redundancy only.
