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https://issues.apache.org/jira/browse/GROOVY-12616?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Paul King resolved GROOVY-12616.
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Fix Version/s: 7.0.0-alpha-1
Assignee: Paul King
Resolution: Fixed
> STC rejects a closure or lambda that returns a primitive needing only a
> widening conversion to the SAM's primitive return type
> ------------------------------------------------------------------------------------------------------------------------------
>
> Key: GROOVY-12616
> URL: https://issues.apache.org/jira/browse/GROOVY-12616
> Project: Groovy
> Issue Type: Bug
> Affects Versions: 4.0.33, 5.0.8, 6.0.0
> Reporter: Scott Murphy Heiberg
> Assignee: Paul King
> Priority: Major
> Fix For: 7.0.0-alpha-1
>
>
> {code:groovy}
> import java.util.function.ToLongFunction
> @groovy.transform.CompileStatic
> class C {
> static void main(args) {
> ToLongFunction<String> f = (String s) -> s.length()
> assert f.applyAsLong('abc') == 3L
> }
> }
> {code}
> Actual: {{[Static type checking] - Cannot return value of type int for lambda
> expecting long}}. The same happens under @TypeChecked, with a closure (passed
> for a ToLongFunction parameter, or a closure returning 42 assigned to a
> LongSupplier), for ToDoubleFunction from int, long or float, for char to int,
> and for Integer to long.
> Expected: compiles and runs, as in Java (JLS 5.2 allows a widening primitive
> conversion, optionally after unboxing, in an assignment context) and as with
> the method reference {{C::len}} or method pointer {{C.&len}}. Narrowing (long
> to int) should still be rejected.
> Cause: {{StaticTypeCheckingVisitor.checkReturnType}} accepts a closure or
> lambda return value only when the wrapper of the SAM return type is
> compatible with the wrapper of the value type, and Long is not compatible
> with Integer.
> Seen in 4.0.33, 5.0.8 and 6.0.0.
> PR: https://github.com/apache/groovy/pull/3142
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