FULL PRODUCT VERSION :
java version "1.8.0_112"
Java(TM) SE Runtime Environment (build 1.8.0_112-b15)
Java HotSpot(TM) 64-Bit Server VM (build 25.112-b15, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 10.0.10586]

A DESCRIPTION OF THE PROBLEM :
This code gives a compiler error:

import java.util.List;
import java.util.function.Function;
 
class Test {
    interface Mapper<T, U extends MapperProvider<U>> extends Function<T, U> {}
 
    interface MapperProvider<V> {
    	Mapper<V, ?> provide();
    }
 
    private <V extends MapperProvider<V>> void use(V c) {
    	use2(c.provide().apply(c));
    }
 
    private <W extends MapperProvider<W>> void use2(W c) {
    }
}


When I wrap U and W in a List<>, the code compiles without error:


import java.util.List;
import java.util.function.Function;
 
class Test {
    interface Mapper<T, U extends MapperProvider<U>> extends Function<T, List<U>> {}
 
    interface MapperProvider<V> {
    	Mapper<V, ?> provide();
    }
 
    private <V extends MapperProvider<V>> void use(V c) {
    	use2(c.provide().apply(c));
    }
 
    private <W extends MapperProvider<W>> void use2(List<W> c) {
    }
}

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile each of the code samples.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Both code samples should yield the same compiler status.
ACTUAL -
Different compiler status.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Teust.java:12: error: method use2 in class Test cannot be applied to given types;
    	use2(c.provide().apply(c));
    	^
  required: W
  found: CAP#1
  reason: inference variable W has incompatible bounds
    equality constraints: CAP#1
    lower bounds: MapperProvider<CAP#1>
  where W is a type-variable:
    W extends MapperProvider<W> declared in method <W>use2(W)
  where CAP#1 is a fresh type-variable:
    CAP#1 extends MapperProvider<CAP#1> from capture of ?
1 error

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------

import java.util.List;
import java.util.function.Function;
 
class Test {
    interface Mapper<T, U extends MapperProvider<U>> extends Function<T, U> {}
 
    interface MapperProvider<V> {
    	Mapper<V, ?> provide();
    }
 
    private <V extends MapperProvider<V>> void use(V c) {
    	use2(c.provide().apply(c));
    }
 
    private <W extends MapperProvider<W>> void use2(W c) {
    }
}





import java.util.List;
import java.util.function.Function;
 
class Test {
    interface Mapper<T, U extends MapperProvider<U>> extends Function<T, List<U>> {}
 
    interface MapperProvider<V> {
    	Mapper<V, ?> provide();
    }
 
    private <V extends MapperProvider<V>> void use(V c) {
    	use2(c.provide().apply(c));
    }
 
    private <W extends MapperProvider<W>> void use2(List<W> c) {
    }
}
---------- END SOURCE ----------