v0.15.2

New features:

• Check for partially applied synonyms in kinds, ctors (#4169 by @rhendric)

  This check doesn't prevent any programs from compiling; it just makes
  sure that a more specific PartiallyAppliedSynonym error is raised
  instead of a KindsDoNotUnify error, which could be interpreted as
  implying that a partially applied synonym has a valid kind and would be
  supported elsewhere if that kind is expected.

• Support deriving instances for type synonyms (#4315 by @rhendric)

Bugfixes:

• Do not emit warnings about type wildcards used in binders (patterns). (#4309 by @fsoikin)

  Type wildcards in the following examples no longer trigger a warning:

  f :: Int
  f = 42 # \(x :: _) -> x
  
  g :: Maybe Int
  g = do
    x :: _ <- getX
    pure $ x + 5
  

• Fix issue with unnamed instances using type operators (#4311 by @rhendric)

• Fix incorrect Prim.Int (class Compare) docs: Int & Ordering, not Symbol (#4313 by @JordanMartinez)

• Fix bad interaction between module renaming and inliner (#4322 by @rhendric)

  This bug was triggered when modules that the compiler handles specially
  are shadowed by local constructors. For example, a constructor named
  Prim could have caused references to Prim_1["undefined"] to be
  produced in the compiled code, leading to a reference error at run time.
  Less severely, a constructor named Control_Bind would have caused the
  compiler not to inline known monadic functions, leading to slower and
  less readable compiled code.

• Update Prim docs for Boolean, Int, String/Symbol, Number, Record, and Row (#4317 by @JordanMartinez)

• Fix crash caused by polykinded instances (#4325 by @rhendric)

  A polykinded instance is a class instance where one or more of the type
  parameters has an indeterminate kind. For example, the kind of a in

  instance SomeClass (Proxy a) where ...

  is indeterminate unless it's somehow used in a constraint or functional
  dependency of the instance in a way that determines it.

  The above instance would not have caused the crash; instead, instances needed
  to be of the form

  instance SomeClass (f a) where ...

  in order to cause it.

• Fix bad interaction between newtype deriving and type synonyms (#4315 by @rhendric)

  See #3453.

• Fix bad interaction between instance deriving and type synonyms (#4315 by @rhendric)

  See #4105.

• Fix spurious kind unification error triggered by newtype deriving, type synonyms, and polykinds (#4315 by @rhendric)

  See #4200.

Internal:

• Deploy builds continuously to GitHub and npm (#4306 and #4324 by @rhendric)

  (Builds triggered by changes that shouldn't affect the published package are
  not deployed.)

• Fix incomplete type traversals (#4155 by @rhendric)

  This corrects oversights in some compiler internals that are not known to be
  the cause of any user-facing issues.

• Drop dependency on microlens libraries (#4327 by @rhendric)