[GROOVY-10351] Wrong type argument is inferred on combining use-site variance and diamond operator

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.0-rc-1, 2.5.19, 3.0.13
• Component/s: Static Type Checker
• Assignee: Eric Milles
• Reporter: Thodoris Sotiropoulos
• Created: 08/Nov/21 13:29
• Updated: 12/Sep/22 17:01
• Resolved: 09/Nov/21 21:28

Description

This bug may be related to GROOVY-10337.

I have the following program

class A<T> {
  A(T f, B<T, ? extends T> x){  } 
}

class B<T1, T2> {}

class Test {
  void test() {
    B<Integer, ? extends Integer> x = null;
    A<Integer> y = new A<>(1, x);
  }
}

Actual behaviour

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
test.groovy: 10: [Static type checking] - Incompatible generic argument types. Cannot assign A<? extends java.lang.Object> to: A<java.lang.Integer>
 @ line 10, column 20.
       A<Integer> y = new A<>(1, x);
                      ^

1 error

Expected behaviour

Compile successfully

Tested against master (https://github.com/apache/groovy/commit/de17150ee844a943c070c01c07b81fd547ff074d).

Issue Links

• is related to: GROOVY-10347 STC: lowed bound wildcard inference produces false positives