[GROOVY-10128] Cannot assign closure with long as return type to java.util.function.Function<X, Number>

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.8, 4.0.0-alpha-3
• Fix Version/s: 4.0.0-beta-2
• Component/s: Static compilation, Static Type Checker
• Assignee: Eric Milles
• Reporter: Stefanos Chaliasos
• Created: 08/Jun/21 10:34
• Updated: 03/Feb/22 22:32
• Resolved: 30/Oct/21 15:15

Description

I have the following Groovy program.

import java.util.function.Function;

@groovy.transform.TypeChecked
class Main {
  public static void main(String[] args) {
      Function<String, Number> x = { y ->
          final long d = 1;
          return d;
      };
  }
}

Actual Behavior

The program does not compile, and I get the following error.

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Main.groovy: 6: [Static type checking] - Incompatible generic argument types. Cannot assign java.util.function.Function <java.lang.String, java.lang.Long> to: java.util.function.Function <String, Number>
 @ line 6, column 36.
         Function<String, Number> x = { y ->
                                      ^

1 error

Expected Behavior

Compile successfully.

Comment

Note that javac accepts this program.

Affected Version

This programs have been tested with the compiler from the master (commit: 05a39632565bee88949c8db9d56b9f9598321fc2), 4.0.0-alpha-3, and 3.0.8.