[GROOVY-6671] Types not inferred when coercing closures of generic method return type

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.3.0
• Fix Version/s: 2.3.0-rc-1
• Component/s: Static Type Checker
• Assignee: Jochen Theodorou
• Reporter: Luke Daley
• Created: 04/Apr/14 20:42
• Updated: 06/May/14 02:45
• Resolved: 06/May/14 02:45

Description

I can't quite narrow down the exact cause of this.

This fails:

// Note: this interface must be in different script because of GROOVY-6670
interface Converter<F, T> {
  T convert(F from)
}

class Holder<T> {
  T thing

  Holder(T thing) {
    this.thing = thing
  }

  def <R> Holder<R> convert(Converter<? super T, ? extends R> func1) {
    new Holder(func1.convert(thing))
  }
}

@CompileStatic
void m() {
  new Holder<Integer>(2).convert {
    it
  } convert {
    it.floatValue() // fails, doesn't know 'it' is an Integer
  }
}

m()

However, this works and I can't work out what the difference is.

interface Action<T> {
  void execute(T thing)
}

class Thing<T> {
  T thing
  Thing(T thing) {
    this.thing = thing
  }
  
  void doWith(Action<? super T> action) {
    action.execute(thing)
  }
}


class Container {
  @groovy.transform.CompileStatic 
  static m() {
    makeThing("a") doWith { println it.toUpperCase() } // works
    makeThingFromCallable { "a" } doWith { println it.toUpperCase() } // works
  }
  
  static <T> Thing<? extends T> makeThing(T thing) {
    new Thing<T>(thing)
  }
  
  static <T> Thing<? extends T> makeThingFromCallable(java.util.concurrent.Callable<T> thing) {
    new Thing<T>(thing.call())
  }
  
}

Container.m()