Changelog:
0.49.1:
* Ban Unstable Variables
0.50.0:
* Fix crash with exhaustive match on Generics.
* Fix parameter names not being checked in all circumstances.
* Fix compiler crash to HeapToStack compiler pass.
* Strengthen the ordering for some atomic operations.
* Allow override of return types for FFI functions.
* Don't allow FFI calls in default methods or behaviours.
* Fix MacOS version mismatch warnings when linking pony programs.
* Fix calculation of "is prime" for numbers > 1321.
* Prevent non-opaque structs from being used as behaviour parameters.
* Update to LLVM 12.0.1.
* Added FileMode.u32.
* Changes to Promises Library.
* Remove zlib from libponyc as a dependency.
* Fix compile-time crash related to Pony-specific Optimizations.
* Update FilePath constructors to allow a non-partial way to create a FilePath.
Updated googlebenchmark dependency to 1.5.4
Updated googletest to 1.10.0
Replaced a fetchurl call with a fetchFromGitHub call.
* Don't allow PONYPATH to override standard library (PR #3780)
* Fix bug where Flags.remove could set flags in addition to unsetting them (PR #3777)
* Allow Flags instances to be created with a set bit encoding (PR #3778)
* Fix "iftype" expressions not being usable in lambdas or object literals (PR #3763)
* Fix code generation for variadic FFI functions on arm64 (PR #3768)
* Fix NullablePointer type constraint check being omitted in FFI declarations
* Change to Steed's model of subtyping
* Fix memory corruption with Array.chop and String.chop
* Improve error message for match on structs
* RFC 68: Mandatory FFI declarations
* Change return type of String.add to String iso^
* Improve error message on destructuring of non-tuple types
* Use built-in offset argument to cpointer
* Add IsPrime checker to math package
* Fix compiler crash related to type parameter references
* Fix literal inference through partial function
* Fix partial FFI declarations ignoring partial annotation
* Fix symbol table patching for overriding default methods
* Fix tuple related compiler segfaults
* Create a standalone libponyc on Linux
