Scott Murphy Heiberg created GROOVY-12617:
---------------------------------------------
Summary: SC: a method reference to a functional interface with a
primitive return type fails at bootstrap when the return value needs a Groovy
conversion (e.g. String to boolean)
Key: GROOVY-12617
URL: https://issues.apache.org/jira/browse/GROOVY-12617
Project: Groovy
Issue Type: Bug
Affects Versions: 5.0.8, 4.0.33, 6.0.0
Reporter: Scott Murphy Heiberg
{code:groovy}
import java.util.function.Predicate
@groovy.transform.CompileStatic
class C {
static String str(String s) { s }
static void main(args) {
Predicate<String> p = C::str
assert !p.test('') && p.test('x')
}
}
{code}
Actual: the code compiles, but evaluating the method reference throws
{{java.lang.BootstrapMethodError}}, caused by
{{java.lang.invoke.LambdaConversionException: Type mismatch for lambda expected
return: class java.lang.String is not convertible to boolean}}. The same
happens for every primitive return that the type checker accepts but the JVM
cannot convert: boolean from any reference type or from int, ToDoubleFunction
from a BigDecimal method, and ToIntFunction from a long or Long method.
Expected: the value is converted as in dynamic Groovy, @TypeChecked code and a
method pointer ({{C.&str}}), which all give [false, true] here (Groovy truth).
Cause: the static compiler binds the method directly through LambdaMetafactory,
which converts a return value to a primitive type only by unboxing and widening
primitive conversion.
Seen in 4.0.33, 5.0.8 and 6.0.0.
--
This message was sent by Atlassian Jira
(v10.3.26#10030026)
