[jira] [Updated] (GROOVY-10913) Type inference yields a wrong type even if the type of the associated variable is given

["Eric Milles (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/GROOVY-10913?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Eric Milles updated GROOVY-10913:
---------------------------------
    Priority: Minor  (was: Major)

> Type inference yields a wrong type even if the type of the associated variable is given
> ---------------------------------------------------------------------------------------
>
>                 Key: GROOVY-10913
>                 URL: https://issues.apache.org/jira/browse/GROOVY-10913
>             Project: Groovy
>          Issue Type: Bug
>          Components: Static Type Checker
>            Reporter: Thodoris Sotiropoulos
>            Assignee: Eric Milles
>            Priority: Minor
>
> The following code demonstrates a limitation of type inference in a real-world example.
> I have the following program
> {code}
> import java.util.*;
> import java.util.stream.*;
> class Test {
>     void test() {
>       Stream<Number> x = Arrays.stream(new Integer[]{1}).flatMap((y) ->
>         Arrays.stream(new Long[]{(long) 1}));
>     }
> }
> {code}
> h3. Actual behavior
> {code}
> org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
> test.groovy: 6: [Static type checking] - Incompatible generic argument types. Cannot assign java.util.stream.Stream<java.lang.Long> to: java.util.stream.Stream<java.lang.Number>
>  @ line 6, column 26.
>          Stream<Number> x = Arrays.stream(new Integer[]{1}).flatMap((y) -> Arrays.stream(new Long[]{(long) 1}));
>                             ^
> 1 error
> {code}
> h3. Expected behavior
> Compile successfully
> The code should pass because the signature of the "flatMap" function is "<R> Stream<R> 	flatMap​(Function<? super T,​? extends Stream<? extends R>> mapper)".  And therefore, Function<Integer, Stream<Long>> is a subtype of Function<? super Integer, ? extends Stream<? extends Number>.
> Tested against master (commit: 5a5726342adeb37a6fbaa8cdcbe2d47dee8dc56c)



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