[GROOVY-7719] Type incompatibility of generic placeholders not detected for method called on field

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.4.5
• Component/s: Static Type Checker
• Assignee: Eric Milles
• Reporter: Frank Pavageau
• Created: 23/Dec/15 10:09
• Updated: 21/Sep/21 16:07

Description

While reading the test case for GROOVY-5839, I noticed it did not actually match the reported problem, which is about a method-level generic type shadowing a class-level generic type. However, the real problem is that the code compiles even without the shadowing of the generic type of the class by the method:

class GoodCodeRed<T> {
    Collection<GoodCodeRed<T>> attached = []
    public <U> void attach(GoodCodeRed<U> toAttach) {
        attached.add(toAttach)
    }
}
def g1 = new GoodCodeRed<Integer>()
def g2 = new GoodCodeRed<Integer>()
g1.attach(g2)

T and U are unrelated, the attached.add(toAttach) call should not compile.

Once that is fixed, we can see if the shadowing of the type is also an issue, simply by renaming U to T.

Issue Links

• is related to: GROOVY-5839 Typechecker does not detect shadowed generic parameter
• relates to: GROOVY-7720 Type incompatibility of generic placeholders not detected on assignment