[GROOVY-9635] Generic types get mixed up

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.15, 3.0.4
• Fix Version/s: 4.0.0-alpha-1, 2.5.14, 3.0.6
• Component/s: Static compilation
• Assignee: Eric Milles
• Reporter: Felix Scheinost
• Created: 10/Jul/20 10:10
• Updated: 11/Nov/20 02:01
• Resolved: 05/Sep/20 10:06

Description

When having a generic function inside a generic class with a constraint the generic types somehow get mixed up.

In the following example the variable v should have the type V. But the generated bytecode contains a cast to the constraint on the generic type of the class.

 

import groovy.transform.CompileStatic
import java.util.function.Function

@CompileStatic
class Test<R extends Integer> {
  def <V> V method(Function<Test, V> f) {
    /**
     * org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast object '' with class 'java.lang.String' to class 'java.lang.Integer'
     * 	at Test.traverseFindResult(ConsoleScript4:7)
     * 	at Test$traverseFindResult.call(Unknown Source)
     * 	at ConsoleScript4.run(ConsoleScript4:12)
     */
    def v = f.apply(this) // V v = f.apply(this) doesn't work as well, but directly returning without assignment works
    return v
  }
}

new Test().method(new Function<Test, String>() {
  @Override
  String apply(Test test) {
    ""
  }
})