Christopher Smith created GROOVY-10844:
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Summary: STC mis-tracks generics in type hierarchy
Key: GROOVY-10844
URL: https://issues.apache.org/jira/browse/GROOVY-10844
Project: Groovy
Issue Type: Bug
Components: Static compilation, Static Type Checker
Affects Versions: 4.0.6
Reporter: Christopher Smith
I have a Vavr {{Try}} pipeline of this form:
{code:groovy}
class AttachmentSpec {
// fields
Attachment toAttachment(Ref ref) { ... }
}
Try.success(initialValue)
.mapTry { process(it) } // returns a Map
.map { convertToRef(it) } // returns a Ref.File extends Ref
.recover { new Ref.Uri(it.href) } // Ref.Uri extends Ref
.map(spec::toAttachment)
{code}
On a failure in {{process}}, this pipeline should enter {{recover}} and supply
a {{Ref.Uri}}, then do the final {{map}}. However, this fails with a
{{ClassCastException: cannot convert Ref.Uri to Ref.File}}. Apparently, the
compiler infers {{Ref.Uri}} as the return value from the first {{map}} (which
is legitimate), but then it fails to produce a compile-time error when
{{recover}} presents a then-incompatible {{Ref.File}}. The compiler should
either (ideally) recognize that the desired type is superclass {{Ref}} or, more
simply but at least correctly, produce a compile-time error until a type
witness is inserted (and observed).
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