Coroutines are a stable feature since 1.3. Version requirement on
suspend functions, or functions mentioning suspend function types in the
signature, was needed to prevent older compilers from reading metadata
that they can't properly use. It's not needed anymore because a newer
metadata version prevents older compilers from reading any metadata
altogether.
Also, computing isSuspendOrHasSuspendTypesInSignature took ~0.5% of
backend time on compilation of intellij (related to KT-48233).
Use the version requierement table of the outer DescriptorSerializer
instance when serializing metadata for a class. Pass parent serializer
to DescriptorSerializer.create to make sure the correct table is used.
Serialize nested classes before the outer class in JS and common code,
to make sure requirements are not lost. Also, split
VersionRequirementTest to JVM and JS
#KT-25120 In Progress
Alexander Udalov