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https://issues.apache.org/jira/browse/GROOVY-9803?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Paul King closed GROOVY-9803.
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> Static type checker forgets nested generic types
> ------------------------------------------------
>
> Key: GROOVY-9803
> URL: https://issues.apache.org/jira/browse/GROOVY-9803
> Project: Groovy
> Issue Type: Bug
> Components: Static Type Checker
> Affects Versions: 3.0.6
> Reporter: Christopher Smith
> Assignee: Eric Milles
> Priority: Major
> Fix For: 4.0.0-alpha-2, 3.0.8
>
> Time Spent: 1.5h
> Remaining Estimate: 0h
>
> When using a nested generic type (for example, from Vavr {{Try<Option<T>}}),
> Groovy forgets the value of the nested type parameter, simply tagging
> {{Object}} instead of {{T}}.
> {code:java}
> import io.vavr.control.Option;
> import io.vavr.control.Try;
> public class GenericInJava {
> public static void main(String[] args) {
> Try.success(123)
> .map(Option::of)
> .map(o -> o.get().intValue()); // happy; correctly identifies
> o as Option<Integer>
> }
> }
> {code}
> {code:groovy}
> import groovy.transform.CompileStatic
> import io.vavr.control.Option
> import io.vavr.control.Try
> @CompileStatic
> class GenericInGroovy {
> static void main(String[] args) {
> Try.success(123)
> .map(Option::of)
> .map(o -> o.get().intValue()) // produces error below
> }
> }
> {code}
> {code}
> Groovy:[Static type checking] - Cannot find matching method
> java.lang.Object#intValue(). Please check if the declared type is correct and
> if the method exists.
> {code}
> Explicitly inserting a type witness {{.<Option<Integer>>map(Option::of)}}
> succeeds. Oddly enough, using {{.map({ Option.of(it) })}} also works (maybe
> it's an interaction glitch involving method references specifically?).
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