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https://issues.apache.org/jira/browse/GROOVY-5839?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15068184#comment-15068184
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Frank Pavageau commented on GROOVY-5839:
----------------------------------------
I'm not sure that's fixed actually, because the test case tests a different
scenario:
{code}
public class GoodCodeRed<T> {
Collection<GoodCodeRed<T>> attached = []
public <T> void attach(GoodCodeRed<T> toAttach) {
attached.add(toAttach)
}
static void foo() {
def g1 = new GoodCodeRed<Long>()
def g2 = new GoodCodeRed<Integer>()
g1.attach(g2);
}
}
GoodCodeRed.foo()
{code}
The point is not that shouldn't be able to call {{attach()}} on an instance
parameterized by {{Long}} with a argument parameterized by {{Integer}}, it's
that {{T}} in the context of the method is not the same as {{T}} in the context
of the class.
The same class in Java (without the static method):
{code}
import java.util.ArrayList;
import java.util.Collection;
public class GoodCodeRed<T> {
private Collection<GoodCodeRed<T>> attached = new ArrayList<>();
public <T> void attach(GoodCodeRed<T> toAttach) {
attached.add(toAttach);
}
}
{code}
fails to compile the {{attach()}} method itself:
{noformat}
GoodCodeRed.java:6: error: incompatible types: GoodCodeRed<T#1> cannot be
converted to GoodCodeRed<T#2>
attached.add(toAttach);
^
where T#1,T#2 are type-variables:
T#1 extends Object declared in method <T#1>attach(GoodCodeRed<T#1>)
T#2 extends Object declared in class GoodCodeRed
{noformat}
It's not the compilation of the usage of {{GoodCodeRed}} which should fail, but
of its implementation, as if it were written like:
{code}
public class GoodCodeRed<T> {
Collection<GoodCodeRed<T>> attached = []
public <U> void attach(GoodCodeRed<U> toAttach) {
attached.add(toAttach)
}
}
{code}
without the type shadowing. {{T}} and {{U}} are not related, neither are
{{T#1}} and {{T#2}}.
Should I open a new bug?
> Typechecker does not detect shadowed generic parameter
> ------------------------------------------------------
>
> Key: GROOVY-5839
> URL: https://issues.apache.org/jira/browse/GROOVY-5839
> Project: Groovy
> Issue Type: Bug
> Components: Static Type Checker
> Affects Versions: 2.0.5
> Reporter: Dimitar Dimitrov
> Assignee: Jochen Theodorou
> Fix For: 2.1.7, 2.2.0-beta-2
>
>
> The typechecker does not realize that the <T> of the method shadows the <T>
> of the class and compiles this code without warning. The same code does not
> typecheck in Java.
> {code}
> public class GoodCodeRed<T> {
> Collection<GoodCodeRed<T>> attached
> @groovy.transform.CompileStatic
> public <T> void attach(GoodCodeRed<T> toAttach) {
> attached.add(toAttach)
> }
> }
> {code}
> See also http://youtrack.jetbrains.com/issue/IDEA-96606
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