[GROOVY-10317] Type variable substitution does not work properly on parameterized function's return type

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.0-beta-2, 3.0.13
• Component/s: Static Type Checker
• Assignee: Eric Milles
• Reporter: Thodoris Sotiropoulos
• Created: 19/Oct/21 11:28
• Updated: 13/Sep/22 17:17
• Resolved: 01/Nov/21 17:29

Description

I have the following program

class A<T1, T2> {
  void m1(T1 x) {}

  void test() {
    var x = new B();
    T2 y = null;
    (new A<T2, T2>()).m1(x.m2(y));
  }
  
}

class B {
  <X, Y> X m2(Y x) { return null; }
}

Actual behaviour

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
test.groovy: 8: [Static type checking] - Cannot call A#m1(T2) with arguments [#X]
 @ line 8, column 5.
       (new A<T2, T2>()).m1(x.m2(y));
       ^

1 error

Expected behaviour

Compile successfully.

*Note*: If I change the expected type of parameter `x` in method `m1(T1 x)` to `m1(T2 x`), the program compiles as expected.

Tested against master