The following code compiles with Java 8 but not with Java 9:
public class CompileErrJdk9 { @FunctionalInterface public interface Closure<R> { R apply(); } @FunctionalInterface public interface VoidClosure { void apply(); } static <R> R call(Closure<R> closure) { return closure.apply(); } static void call(VoidClosure closure) { call(() -> { closure.apply(); return null; }); } static <T> void myMethod(T data) { System.out.println(data); } public static void main(String[] args) { call(() -> myMethod("hello")); //compile error in jdk9 } } This is the error:
CompileErrJdk9.java:24: error: incompatible types: inference variable R has incompatible bounds call(() -> myMethod("hello")); //compile error in jdk9 ^ upper bounds: Object lower bounds: void where R is a type-variable: R extends Object declared in method <R>call(Closure<R>) 1 error I've narrowed it down to the type parameter <T> of myMethod; if I drop it and use Object for the parameter type the code compiles. Declaring myMethod as static <T> void myMethod() { } fails as well (in 9 only) even though I'm not using the type parameter.
I've checked the Java 9 release notes and searched for an explanation for this behaviour but did not find anything. Am I correct to assume this is a bug in JDK9, or am I missing something?
