[GROOVY-9996] Cannot infer correct type argument when using subtyping

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.8, 4.0.0-alpha-3
• Component/s: Static compilation, Static Type Checker
• Assignee: Eric Milles
• Reporter: Stefanos Chaliasos
• Created: 22/Mar/21 08:36
• Updated: 08/Jun/21 09:17
• Resolved: 25/Mar/21 00:32

Description

I have the following Groovy program.

@groovy.transform.CompileStatic
public class Main {
  public static void main(String[] args) {
    Foo foo = new Bar()
    def x = new A<>(foo)
    bar(x)
  }

  public static void bar(A<Foo> f) {}
}

class A<T> {
  T f;
  public A(T f) {
    this.f = f;
  }
}

class Foo {}
class Bar extends Foo {}

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] - Cannot call Main#bar(A <Foo>) with arguments [A <Bar>]
 @ line 6, column 5.
       bar(x)
       ^

1 error

Expected Behavior

Compile successfully.

Affected Version

This should be a regression. The program compiles with 3.0.7 and 4.0.0-alpha-2, but fails with the compiler from Master (commit: e69c874e1a6a3cdeb236bad6a6faa061a30c88ca).