[GROOVY-8202] void tail calls in closures break @CompileStatic type inference

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.4.10
• Fix Version/s: 2.5.15, 4.0.0-beta-1, 3.0.9
• Component/s: Static compilation
• Assignee: Eric Milles
• Reporter: Joan Karadimov
• Created: 23/May/17 19:08
• Updated: 03/Feb/22 22:34
• Resolved: 09/May/21 15:23

Description

Consider this piece of code:

void f() {
}

@CompileStatic
String test1() {
	Closure<String> x = {
		if (true) {
			"asd"
		} else {
			f()
			null
		}
	}
	x.call()
}

@CompileStatic
String test2() {
	Closure<String> x = { // Cannot assign Closure<Object> to Closure<String>
		if (true) {
			"asd"
		} else {
			f()
		}
	}
	x.call()
}

@CompileStatic
String test3() {
	if (true) {
		"asd"
	} else {
		f()
	}
}

The code in test1 compiles correctly. The type of the closure in test2 is inferred as Closure<Object> and that results in a static type checking error. There is an inconsistency here - in test3 the type inference yields String.

Basically - null s are not considered when the type is inferred. Calls to void methods should not be either.