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https://issues.apache.org/jira/browse/GROOVY-8459?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Eric Milles closed GROOVY-8459.
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Resolution: Information Provided
{{Closure}}'s {{run()}} method simply delegates to {{call()}} and discards the
return value. Method selection prefers Runnable over Callable due to interface
distance. The parameter disambiguation is not considered -- GROOVY-10714
discusses this possibility.
There is no check for return to influence method selection. There are so many
implicit return cases that I think it would cause more confusion if we started
doing this.
To force the selection of "foo(Callable)" over "foo(Runnable)" you probably
need to use a typecast and static compilation.
> Closure with return value coercion problem in overloaded methods
> ----------------------------------------------------------------
>
> Key: GROOVY-8459
> URL: https://issues.apache.org/jira/browse/GROOVY-8459
> Project: Groovy
> Issue Type: Bug
> Components: Compiler
> Affects Versions: 2.4.13
> Reporter: Evermind
> Assignee: Eric Milles
> Priority: Minor
>
> Hi,
> In following method overloading code, a closure with return value are
> coerced to type Runnable, whose only method returns void. I think a compile
> warning or error should be issued here.
> {code:groovy}
> import java.util.concurrent.Callable
> class Foo {
> def <T> void foo(Callable<T> c) {
> println "Callable foo"
> }
> void foo(Runnable r) {
> println "Runnable foo"
> }
> def test() {
> // ---> BOTH foo()s are resolved to foo(Runnable) overload version,
> followed closures coerced to Runnable, dispite the fact that the 1st closure
> has return value.
> foo {
> return 1 // Runnable's single method return type is void,
> should not match this closure with return value.
> }
> foo {
> }
> }
> static void main(String[] args) {
> new Foo().test()
> }
> }
> {code}
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