[jira] [Created] (GROOVY-9956) Cannot infer correct type argument when passing a subtype of the declared type argument

["Stefanos Chaliasos (Jira)" <ji...@apache.org>]

Stefanos Chaliasos created GROOVY-9956:
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             Summary: Cannot infer correct type argument when passing a subtype of the declared type argument
                 Key: GROOVY-9956
                 URL: https://issues.apache.org/jira/browse/GROOVY-9956
             Project: Groovy
          Issue Type: Bug
          Components: Static compilation, Static Type Checker
    Affects Versions: 4.0.0-alpha-2, 3.0.7
            Reporter: Stefanos Chaliasos


I have the following Groovy program.
{code:groovy}
class Foo<T> {
    T f;
    Foo (T f) {
      this.f = f;
    }

}

interface Bar{}
class Baz<T> implements Bar {}

@groovy.transform.TypeChecked
class Main  {
  public static void main(String[] args) {
    Foo<Bar> x1 = new Foo<Bar>(new Baz<Integer>()) // Compiles
    Foo<Bar> x2 = new Foo<>(new Baz<Integer>()) // Does not compile
  }
}
{code}
h2. Actual Behavior

The program does not compile, and I get the following error.
{code:java}
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Main.groovy: 16: [Static type checking] - Incompatible generic argument types. Cannot assign Foo <Baz> to: Foo <Bar>
 @ line 16, column 19.
       Foo<Bar> x2 = new Foo<>(new Baz<Integer>())
                     ^

1 error

{code}
h2. Expected Behavior

Compile successfully.
h2. Affected Version

I have also tested it with the compiler from Master (commit: 666627b3be7718e3265fc42b473060bc73f42e2f).
h2. Comment

If I remove the type parameter from Baz, then it only fails when compiled with the compiler from the Master.
 Specifically, the following test case compiles with 3.0.7 and 4.0.0-alpha-2 compilers but fails with the same message as the previous test case when using the compiler from the Master.
{code:groovy}
class Foo<T> {
    T f;
    Foo (T f) {
      this.f = f;
    }

}

interface Bar{}
class Baz implements Bar {}

@groovy.transform.TypeChecked
class Main  {
  public static void main(String[] args) {
    Foo<Bar> x1 = new Foo<Bar>(new Baz()) // Compiles
    Foo<Bar> x2 = new Foo<>(new Baz()) // Does not compile
  }
}
{code}



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