Wildcard type argument is not compatible with type variable upper bound

Issue #189 resolved
Jesper Öqvist created an issue

ExtendJ 8.0.1-154-gaf5cf06 Java SE 8

When a generic type is parameterized with a wildcard type argument, the type argument should be compatible with the upper bound of the type variable.

In the following test case, the I type uses upper bound Thing for type variable T, thus I<?> should be compatible with I<? extends Thing>, but it is not:

// Test method invocation type conversion.
// .result=COMPILE_PASS

class Thing {}
interface I<T extends Thing> {}

class Test {

  static void foo(I<? extends Thing> i) { }

  void m(I<?> i) {
    foo(i);  // Should work fine: the upper bound of T is Thing.

ExtendJ reports the following error:

tests/generics/method_11p/Test.java:12: error: no method named foo(I<wildcards.?>) in Test matches. However, there is a method foo(I<wildcards.? extends Thing>)

Javac does not report an error for this test case.

Comments (1)

  1. Jesper Öqvist reporter

    Improve handling of wildcard in parameterizations

    Wildcard type arguments were not substituted for their upper bound when testing if a parameterization was contained in another parameterization.

    fixes #189 (bitbucket)

    → <<cset e9164274b15c>>

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