FULL PRODUCT VERSION :
java version "1.8.0-ea"
Java(TM) SE Runtime Environment (build 1.8.0-ea-b118)
Java HotSpot(TM) Server VM (build 25.0-b60, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Linux laptop 3.2.0-57-generic #87-Ubuntu SMP Tue Nov 12 21:38:12 UTC 2013 i686 i686 i386 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
When defining function and wraps lambda's body in parentheses as follows (see "inc" function):
        final Function2<Integer, Integer, Integer> add = (x, y) -> x + y;
        final Function1<Integer, Integer> inc = x -> (add.apply(x, 1));
It compiles but JVM fails in runtime with the following error:

Exception in thread "main" java.lang.VerifyError: Bad return type
Exception Details:
  Location:
    TestFailing.lambda$main$1(LTestFailing$Function2;Ljava/lang/Integer;)Ljava/lang/Integer; @11: areturn
  Reason:
    Type 'java/lang/Object' (current frame, stack[0]) is not assignable to 'java/lang/Integer' (from method signature)
  Current Frame:
    bci: @11
    flags: { }
    locals: { 'TestFailing$Function2', 'java/lang/Integer' }
    stack: { 'java/lang/Object' }
  Bytecode:
    0000000: 2a2b 04b8 0005 b900 0803 00b0

at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2680)
at java.lang.Class.getMethod0(Class.java:2929)
at java.lang.Class.getMethod(Class.java:1763)
at sun.launcher.LauncherHelper.validateMainClass(LauncherHelper.java:544)
at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:526)


ADDITIONAL REGRESSION INFORMATION:
java version "1.8.0-ea"
Java(TM) SE Runtime Environment (build 1.8.0-ea-b118)
Java HotSpot(TM) Server VM (build 25.0-b60, mixed mode)


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile and run the code below:

public class TestFailing {

    @FunctionalInterface
    public static interface Function1<R, A> {
        R apply(A input);
    }

    @FunctionalInterface
    public static interface Function2<R, A1, A2> {
        R apply(A1 input1, A2 input2);
    }

    public static void main(String[] args) {
        final Function2<Integer, Integer, Integer> add = (x, y) -> x + y;
        final Function1<Integer, Integer> inc = x -> (add.apply(x, 1));
        System.out.println(inc.apply(0));
    }

}


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
"1" in console.
ACTUAL -
Exception in thread "main" java.lang.VerifyError: Bad return type
Exception Details:
  Location:
    TestFailing.lambda$main$1(LTestFailing$Function2;Ljava/lang/Integer;)Ljava/lang/Integer; @11: areturn
  Reason:
    Type 'java/lang/Object' (current frame, stack[0]) is not assignable to 'java/lang/Integer' (from method signature)
  Current Frame:
    bci: @11
    flags: { }
    locals: { 'TestFailing$Function2', 'java/lang/Integer' }
    stack: { 'java/lang/Object' }
  Bytecode:
    0000000: 2a2b 04b8 0005 b900 0803 00b0

at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2680)
at java.lang.Class.getMethod0(Class.java:2929)
at java.lang.Class.getMethod(Class.java:1763)
at sun.launcher.LauncherHelper.validateMainClass(LauncherHelper.java:544)
at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:526)

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Exception in thread "main" java.lang.VerifyError: Bad return type
Exception Details:
  Location:
    TestFailing.lambda$main$1(LTestFailing$Function2;Ljava/lang/Integer;)Ljava/lang/Integer; @11: areturn
  Reason:
    Type 'java/lang/Object' (current frame, stack[0]) is not assignable to 'java/lang/Integer' (from method signature)
  Current Frame:
    bci: @11
    flags: { }
    locals: { 'TestFailing$Function2', 'java/lang/Integer' }
    stack: { 'java/lang/Object' }
  Bytecode:
    0000000: 2a2b 04b8 0005 b900 0803 00b0

at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2680)
at java.lang.Class.getMethod0(Class.java:2929)
at java.lang.Class.getMethod(Class.java:1763)
at sun.launcher.LauncherHelper.validateMainClass(LauncherHelper.java:544)
at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:526)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public class TestFailing {

    @FunctionalInterface
    public static interface Function1<R, A> {
        R apply(A input);
    }

    @FunctionalInterface
    public static interface Function2<R, A1, A2> {
        R apply(A1 input1, A2 input2);
    }

    public static void main(String[] args) {
        final Function2<Integer, Integer, Integer> add = (x, y) -> x + y;
        final Function1<Integer, Integer> inc = x -> (add.apply(x, 1));
        System.out.println(inc.apply(0));
    }

}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Don't use parentheses to wrap lambda's body:

public class TestWorking {

    @FunctionalInterface
    public static interface Function1<R, A> {
        R apply(A input);
    }

    @FunctionalInterface
    public static interface Function2<R, A1, A2> {
        R apply(A1 input1, A2 input2);
    }

    public static void main(String[] args) {
        final Function2<Integer, Integer, Integer> add = (x, y) -> x + y;
        final Function1<Integer, Integer> inc = x -> add.apply(x, 1);
        System.out.println(inc.apply(0));
    }

}