[GROOVY-10646] STC: outer class type parameter inference

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 4.0.5
• Component/s: Static Type Checker
• Assignee: Eric Milles
• Reporter: Eric Milles
• Created: 01/Jun/22 15:45
• Updated: 10/Feb/23 21:39
• Resolved: 01/Aug/22 20:02

Description

Consider the following (extracted from mybatis SelectDSLCompleter):

class Model {
}
interface Output<T> {
  T build()
}
abstract class Input<T> extends QueryDSL<Inner> implements Output<T> {
  class Inner implements Output<T> {
    @Override T build() { }
  }
}

abstract class QueryDSL<X> {
  abstract X where()
}

@FunctionalInterface
interface Func extends Function<Input<Model>, Output<Model>> {
}

void select(Func func) {
}

@groovy.transform.TypeChecked
void test() {
  select { input -> input.where() } // Cannot return value of type Inner for closure expecting Output<Model>
}

"input" is inferred correctly to be of type "Input<Model>" which should lead to an "Inner" return type for "where()" that implements "Output<Model>". Some context is lost along the way and "Output<Object>" is inferred instead.

https://github.com/groovy/groovy-eclipse/issues/1364