'SuspendFunction$n' class descriptors are created on demand by KotlinBuiltIns (and cached).
On serialization, types constructed with 'SuspendFunction$n' are written as 'Function$n' with extra flag (SUSPEND_TYPE).
On deserialization, corresponding 'SuspendFunction$n' classes are used.
This is a way for future compilers to cause previous compilers to report
diagnostics on usages of some declarations. Diagnostic can have a message
(and/or error code), level (error, warning, or completely hide the declaration
from the resolution), and Kotlin version, since which the diagnostic should no
longer be reported
Compilation of top level functions/properties/typealiases results in a bunch of
different .kotlin_metadata files, so we need to store names of these files to
avoid scanning the file system in the compiler when loading code compiled by
K2MetadataCompiler.
For this, we reuse the PackageTable protobuf message, which is already used for
exactly the same purpose in the JVM back-end
Since public type aliases will supposedly be more common than internal ones, it
makes sense to save on writing flags for the former rather than the latter
Dmitry Petrov