[GROOVY-10367] STC fails to infer the correct type for type variable in the presence of the diamond operator and bounded polymorphism

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.2, 2.5.19, 3.0.13
• Component/s: Static Type Checker
• Assignee: Eric Milles
• Reporter: Thodoris Sotiropoulos
• Created: 15/Nov/21 09:21
• Updated: 10/Sep/22 18:31
• Resolved: 15/Mar/22 17:36

Description

This issue may be related to GROOVY-10343.

I have the following program

class A<Z, P extends Z> {
  Z f;
  A(Z f) {}
}

class B<Z extends Number> {
  Z f;

  void test() {
    f = new A<>((Z) null).f;
  }
}

Actual behaviour

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
test.groovy: 10: [Static type checking] - Cannot assign value of type java.lang.Object to variable of type Z
 @ line 10, column 9.
       f = new A<>((Z) null).f;
           ^

1 error

Expected behaviour

Compile successfully

NOTE: Replacing `Z extends Number` with `Z` leads to a successful compilation.

Tested against master (https://github.com/apache/groovy/commit/cf2f77fb033a10d36c4db3a7ff07a2b04631afcf)