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https://issues.apache.org/jira/browse/GROOVY-12620?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18139874#comment-18139874
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Scott Murphy Heiberg commented on GROOVY-12620:
-----------------------------------------------
Master now accepts these: the check GROOVY-12616 gave a value returned to a
primitive functional interface type allows a constant that fits a byte or
short. A constant that does not fit is reported as "Possible loss of
precision", and char is not range checked (GROOVY-12648).
https://github.com/apache/groovy/pull/3146 now only adds the tests.
> STC rejects a closure or lambda returning an int constant for a byte, short
> or char SAM return type
> ---------------------------------------------------------------------------------------------------
>
> Key: GROOVY-12620
> URL: https://issues.apache.org/jira/browse/GROOVY-12620
> Project: Groovy
> Issue Type: Bug
> Affects Versions: 4.0.33, 5.0.8, 6.0.0
> Reporter: Scott Murphy Heiberg
> Priority: Major
>
> {code:groovy}
> interface S { short get() }
> interface B { byte get() }
> interface C { char get() }
> @groovy.transform.TypeChecked // or @CompileStatic
> void test() {
> S s = () -> 1
> B b = { -> 2 }
> C c = () -> 65
> assert s.get() == (short) 1 && b.get() == (byte) 2 && c.get() == (char) 65
> }
> test()
> {code}
> Actual:
> {noformat}
> [Static type checking] - Cannot return value of type int for lambda expecting
> short
> [Static type checking] - Cannot return value of type int for closure
> expecting byte
> [Static type checking] - Cannot return value of type int for lambda expecting
> char
> {noformat}
> Expected: the script compiles and runs. Java accepts these lambdas, because
> JLS 5.2 allows narrowing an int constant that fits the target type in an
> assignment context, and a lambda result expression is in an assignment
> context. Groovy already accepts a short variable or a short method return
> initialised from such a constant, and dynamic Groovy runs the script. A
> constant that does not fit, such as 70000 for short, or a non-constant int
> must still be rejected.
> The closure/lambda return check in StaticTypeCheckingVisitor.checkReturnType
> accepts only a return type that is compatible after wrapping, so int is never
> accepted where byte, short or char is expected.
> Seen in 4.0.33, 5.0.8 and 6.0.0.
> PR: https://github.com/apache/groovy/pull/3146
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