Bug findings with Type Erasure and Type Overwriting Mutation

Kotlin

• #1 NI: Inferred type does not respect the bound of type variable
  
  Link: https://youtrack.jetbrains.com/issue/KT-48765
  Date found: 2021-09-15
  Status: Open
  Resolution date: 2022-04-28
  Symptom: Unexpected runtime behavior
  Test case:

  
  open class A<T1, T2> {}
  class B {
      fun <T1: Number, T2: A<Float, T1>> foo(x1: T2, x2: T1) {}
  }
  class C<T: D, T2>(val x: T, val y: T2) {
      fun test() {
          B().foo(x, foo())
      }
  }
  open class D: A<Float, Number>()
  fun <T: String> foo(): T  {
      return "" as T // this cast is safe because String is final.
  }
  fun main() {
      C(D(), 10.5).test()
  }
  
  

  Test Case Characteristics: Parameterized class, Parameterized type, Parameterized function, Bounded type parameter, Type argument inference, Subtyping
  
  

Groovy

• #2 STC misses type error when calling a vararg method -- Fixed
  
  Link: https://issues.apache.org/jira/browse/GROOVY-10086
  Date found: 2021-05-13
  Status: Closed
  Resolution: Fixed
  Resolution date: 2021-05-16
  Symptom: Unexpected runtime behavior
  Test case:

  
  class Foo {}
  class X<T> {
    T f;
    X(T f) {
      this.f = f;
    }
    T getF() {
      this.f;
    }
  }
  class A {
    void foo(int x, X<Foo>... y) {
      Foo foo = y[0].getF(); // ClastCastException at runtime
    }
  }
  public class Main {
      public static void main(String[] args) {
        A a = new A();
        a.foo(1, new X<>(1));
      }
  }
  
  

  Test Case Characteristics: Parameterized class, Parameterized type, Variable argument, Type argument inference
  Fix Commit(s):

  • https://github.com/apache/groovy/commit/e8456448e1