[GROOVY-11004] Incompatible generic argument types when mixing diamond operator in parameterized function

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Component/s: Static Type Checker
• Assignee: Unassigned
• Reporter: Thodoris Sotiropoulos
• Created: 07/Apr/23 13:44
• Updated: 15/Apr/23 15:50

Description

This might be a regression, as Groovy 4.0.10 accepts the program.

I have the following program

import java.util.*;

class Main {
  static final void test() {
    Map<Number, String> x = null;
    Map<Number, String> y = Collections.unmodifiableNavigableMap(new TreeMap<>(x));
  }
}

Actual behavior

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
test.groovy: 6: [Static type checking] - Incompatible generic argument types. Cannot assign java.util.NavigableMap<java.lang.Object, java.lang.Object> to: java.util.Map<java.lang.Number, java.lang.String>
 @ line 6, column 29.
       Map<Number, String> y = Collections.unmodifiableNavigableMap(new TreeMap<>(x));
                               ^

1 error

Expected behavior

Compile successfully