[GROOVY-9971] @TypeChecked: Closure<String> no longer compatible with Closure<GString> argument

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.7
• Fix Version/s: 4.0.0-alpha-3, 3.0.9, 2.5.16
• Component/s: Compiler
• Environment: Windows 10 ; jdk-11.0.10.9-hotspot ; IntelliJ 2020.3.2
• Assignee: Eric Milles
• Reporter: mgroovy
• Created: 08/Mar/21 12:07
• Updated: 30/May/23 01:27
• Resolved: 07/Apr/21 13:30

Description

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

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()
	}
}

Issue Links

• relates to: GROOVY-11051 Static compiler does not coerce Groovy truth from closures
• relates to: GROOVY-10792 Declared generic parameter on method not transferred to Closure