FULL PRODUCT VERSION :
java version "1.8.0_20"
Java(TM) SE Runtime Environment (build 1.8.0_20-b26)
Java HotSpot(TM) 64-Bit Server VM (build 25.20-b23, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Linux padd 3.11.10-17-desktop #1 SMP PREEMPT Mon Jun 16 15:28:13 UTC 2014 (fba7c1f) x86_64 x86_64 x86_64 GNU/Linux


A DESCRIPTION OF THE PROBLEM :
When compiling the following testcase, we get the following error in javac.

import java.util.Collection;
import java.util.List;
import java.util.Optional;
import java.util.function.Function;

import static java.util.Arrays.asList;

public class TestCase {
    public static void main(String... args) {
        new Baz();
    }
}

class Foo<T> {
    public Foo(List<Function<T, Collection>> ts) {

    }
}

class Baz extends Foo<Bar> {
    public Baz() {
        super(asList(Bar::foos));
    }
}

class Bar {
    Optional<List<String>> foos() {
        return Optional.empty();
    }
}

/*
An exception has occurred in the compiler (1.8.0_20). Please file a bug at the Java Developer Connection (http://java.sun.com/webapps/bugreport) after checking the Bug Parade for duplicates. Include your program and the following diagnostic in your report. Thank you.
java.lang.NullPointerException
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.visitIdent(Flow.java:2380)
        at com.sun.tools.javac.tree.JCTree$JCIdent.accept(JCTree.java:2011)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scan(Flow.java:1376)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scanExpr(Flow.java:1627)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.visitApply(Flow.java:2235)
        at com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1465)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scan(Flow.java:1376)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scanExpr(Flow.java:1627)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scanExprs(Flow.java:1639)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.visitApply(Flow.java:2236)
        at com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1465)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scan(Flow.java:1376)
        at com.sun.tools.javac.tree.TreeScanner.visitExec(TreeScanner.java:175)
        at com.sun.tools.javac.tree.JCTree$JCExpressionStatement.accept(JCTree.java:1296)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scan(Flow.java:1376)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:57)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.visitBlock(Flow.java:1846)
        at com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:909)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scan(Flow.java:1376)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.visitMethodDef(Flow.java:1783)
        at com.sun.tools.javac.comp.Flow$AssignAnalyzer.visitMethodDef(Flow.java:2560)
        at com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:778)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scan(Flow.java:1376)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.visitClassDef(Flow.java:1736)
        at com.sun.tools.javac.comp.Flow$AssignAnalyzer.visitClassDef(Flow.java:2539)
        at com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:693)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scan(Flow.java:1376)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.analyzeTree(Flow.java:2423)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.analyzeTree(Flow.java:2406)
        at com.sun.tools.javac.comp.Flow.analyzeTree(Flow.java:211)
        at com.sun.tools.javac.main.JavaCompiler.flow(JavaCompiler.java:1327)
        at com.sun.tools.javac.main.JavaCompiler.flow(JavaCompiler.java:1296)
        at com.sun.tools.javac.main.JavaCompiler.compile2(JavaCompiler.java:901)
        at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:860)
        at com.sun.tools.javac.main.Main.compile(Main.java:523)
        at com.sun.tools.javac.main.Main.compile(Main.java:381)
        at com.sun.tools.javac.main.Main.compile(Main.java:370)
        at com.sun.tools.javac.main.Main.compile(Main.java:361)
        at com.sun.tools.javac.Main.compile(Main.java:56)
        at com.sun.tools.javac.Main.main(Main.java:42)

*/

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile specified testcase with javac 1.8.0u20

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Either it compiles successfully, or a compile failure with suitable error message.
ACTUAL -
NPE within javac

ERROR MESSAGES/STACK TRACES THAT OCCUR :
java.lang.NullPointerException
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.visitIdent(Flow.java:2380)
        at com.sun.tools.javac.tree.JCTree$JCIdent.accept(JCTree.java:2011)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scan(Flow.java:1376)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scanExpr(Flow.java:1627)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.visitApply(Flow.java:2235)
        at com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1465)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scan(Flow.java:1376)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scanExpr(Flow.java:1627)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scanExprs(Flow.java:1639)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.visitApply(Flow.java:2236)
        at com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1465)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scan(Flow.java:1376)
        at com.sun.tools.javac.tree.TreeScanner.visitExec(TreeScanner.java:175)
        at com.sun.tools.javac.tree.JCTree$JCExpressionStatement.accept(JCTree.java:1296)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scan(Flow.java:1376)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:57)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.visitBlock(Flow.java:1846)
        at com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:909)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scan(Flow.java:1376)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.visitMethodDef(Flow.java:1783)
        at com.sun.tools.javac.comp.Flow$AssignAnalyzer.visitMethodDef(Flow.java:2560)
        at com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:778)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scan(Flow.java:1376)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.visitClassDef(Flow.java:1736)
        at com.sun.tools.javac.comp.Flow$AssignAnalyzer.visitClassDef(Flow.java:2539)
        at com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:693)
        at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
        at com.sun.tools.javac.comp.Flow$BaseAnalyzer.scan(Flow.java:398)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.scan(Flow.java:1376)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.analyzeTree(Flow.java:2423)
        at com.sun.tools.javac.comp.Flow$AbstractAssignAnalyzer.analyzeTree(Flow.java:2406)
        at com.sun.tools.javac.comp.Flow.analyzeTree(Flow.java:211)
        at com.sun.tools.javac.main.JavaCompiler.flow(JavaCompiler.java:1327)
        at com.sun.tools.javac.main.JavaCompiler.flow(JavaCompiler.java:1296)
        at com.sun.tools.javac.main.JavaCompiler.compile2(JavaCompiler.java:901)
        at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:860)
        at com.sun.tools.javac.main.Main.compile(Main.java:523)
        at com.sun.tools.javac.main.Main.compile(Main.java:381)
        at com.sun.tools.javac.main.Main.compile(Main.java:370)
        at com.sun.tools.javac.main.Main.compile(Main.java:361)
        at com.sun.tools.javac.Main.compile(Main.java:56)
        at com.sun.tools.javac.Main.main(Main.java:42)


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.util.Collection;
import java.util.List;
import java.util.Optional;
import java.util.function.Function;

import static java.util.Arrays.asList;

public class TestCase {
    public static void main(String... args) {
        new Baz();
    }
}

class Foo<T> {
    public Foo(List<Function<T, Collection>> ts) {

    }
}

class Baz extends Foo<Bar> {
    public Baz() {
        super(asList(Bar::foos));
    }
}

class Bar {
    Optional<List<String>> foos() {
        return Optional.empty();
    }
}

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

CUSTOMER SUBMITTED WORKAROUND :
Removing the Optional<T> wrapper avoids the problem. It might be related to the nested generics.