[jira] [Commented] (GROOVY-9971) @TypeChecked: Closure no longer compatible with Closure argument

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

    [ https://issues.apache.org/jira/browse/GROOVY-9971?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17314924#comment-17314924 ] 

Eric Milles commented on GROOVY-9971:
-------------------------------------

During testing, I noticed that for a method that returns String, there is a groovy cast written for each return value.  With that in mind, I was able to implement your original request for closure expressions that are targeted to {{Closure<String>}} or say {{Supplier<String>}}.  The solution requires STC or SC enabled.  You can test using the deployed snapshot: https://github.com/apache/groovy/actions/runs/717127889

With regards to a "stringify" operator.  A cheap solution is "import static java.util.Objects.toString as $", which can be applied like "$(expr)" or "$(expr,'nil')".  A more elaborate solution would be to implement a macro method for "$" as a method name so you could apply {{.toString()}} or {{as String}} to each element of an array or collection or map values.

> @TypeChecked: Closure<String> no longer compatible with Closure<GString> argument
> ---------------------------------------------------------------------------------
>
>                 Key: GROOVY-9971
>                 URL: https://issues.apache.org/jira/browse/GROOVY-9971
>             Project: Groovy
>          Issue Type: Bug
>          Components: Compiler
>    Affects Versions: 3.0.7
>         Environment: Windows 10
> jdk-11.0.10.9-hotspot
> IntelliJ 2020.3.2
>            Reporter: mgroovy
>            Assignee: Eric Milles
>            Priority: Major
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> *Problem*
> A Closure<String> is in Groovy 3 no longer compatible with a closure that returns a GString (or String|GString), even though GString is autoconverted
> to String in Groovy.
> *Expected*
> A Closure returning a GString or a String|GString should be compatible with Closure<String>
> *Sample Code*
> {code:java}
> import groovy.transform.TypeChecked
> import org.junit.Ignore
> import org.junit.Test
> @TypeChecked
> class Groovy3_ClosureOfString_GString_Compatible {
> 	@Test @Ignore
> 	void 'Groovy 3-0-7 Closure with String return type not compatible with GString argument'() {
> 		final x = 123
> 		// Cannot find matching method execStringCls(Closure<groovy.lang.GString>)
> 		assert execStringCls { "x=$x" } == 'x=123'
> 		//assert execStringCls { "x=$x".toString() } == 'x=123'  // works
> 	}
> 	@Test @Ignore
> 	void 'Groovy 3-0-7 Closure with String return type not compatible with GString argument 2'() {
> 		final x = 123
> 		// Cannot find matching method execStringCls(Closure<java.io.Serializable>)
> 		assert execStringCls { false ? 'abc' : "x=$x" } == 'x=123'
> 		//assert execStringCls { true ? 'abc' : "x=$x".toString() } == 'x=123' // works
> 	}
> 	String execStringCls(Closure<String> cls) {
> 		cls()
> 	}
> }
> {code}



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