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https://issues.apache.org/jira/browse/GROOVY-10913?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Eric Milles reassigned GROOVY-10913:
------------------------------------
Assignee: Eric Milles
> 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: Major
>
> 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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