Coersion to Unit from error type leads to misleading type mismatches:
"expected <expected lambda return type> found Unit", despite no user-provided Unit / empty lambda.
These diagnostics were collected, but not reported before, and that had been disguising the issue for a while.
KT-34729 Fixed
Also that commit removes usages of builtins inside
effect system and starts refactoring of functor
composition via composition instead of inheritance.
There are some changes in testdata related to inference of recursive
functions with implicit return types.
After this commit they all are marked as unresolved. It happens because
those functions have DeferredType as return type, and computing this
type produces recursive exception, which provides “typechecker
recursive problem” diagnostic.
Before this commit, function call was completed successfully, because
call completer didn’t computed that type, and computation of DeferredType
were triggered only in `DataFlowAnalyzer.checkType`.
Now, effect system tries to compute that type while wrapping KotlinTypes
into ESTypes, and effect system itself is triggered in in call completer,
so, call completion doesn’t finish and function call is marked as unresolved.
#KT-31364
Mikhail Zarechenskiy