From the Kotlin spec: http://jetbrains.github.io/kotlin-spec/#_type_inference http://jetbrains.github.io/kotlin-spec/#_type_inference "Type inference is conser

From the Kotlin spec: http://jetbrains.github.io/kotlin-spec/#_type_inference http://jetbrains.github.io/kotlin-spec/#_type_inference "Type inference is conservative — it may fail to find suitable assignment of type-arguments to the type-parameters despite that one exist, and the function invocation could be successfully typechecked if the programmer explicitly provided suitable type-arguments." My guess is that what the thesis presents is complete type inference in presence of subtyping that is decidable, efficient, and that yields types with all the nice properties one could hope for (principality, compactness, ...). Which is hard.