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 io.tomosw.bruker.de 3.7.10-1.40-desktop #1 SMP PREEMPT Thu Jul 10 11:22:12 UTC 2014 (9b06319) x86_64 x86_64 x86_64 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
Assertion in javac while compiling classes which compiled fine using jdk8u5

REGRESSION. Last worked in version 8u5

ADDITIONAL REGRESSION INFORMATION:
java version "1.8.0_05"
Java(TM) SE Runtime Environment (build 1.8.0_05-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.5-b02, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile the three files A.java, B.java and C.java

javac A.java B.java C.java

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The files are compiled without errors.
ACTUAL -
A java.lang.AssertionError is thrown in the compiler

ERROR MESSAGES/STACK TRACES THAT OCCUR :
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.AssertionError: isSubClass T
at com.sun.tools.javac.code.Symbol.isSubClass(Symbol.java:447)
at com.sun.tools.javac.code.Symbol.isMemberOf(Symbol.java:456)
at com.sun.tools.javac.code.Symbol$MethodSymbol.overrides(Symbol.java:1469)
at com.sun.tools.javac.code.Types$ImplementationCache.implementationInternal(Types.java:2671)
at com.sun.tools.javac.code.Types$ImplementationCache.get(Types.java:2653)
at com.sun.tools.javac.code.Types.implementation(Types.java:2682)
at com.sun.tools.javac.code.Symbol$MethodSymbol.implementation(Symbol.java:1529)
at com.sun.tools.javac.code.Symbol$MethodSymbol.implementation(Symbol.java:1518)
at com.sun.tools.javac.comp.Resolve.notOverriddenIn(Resolve.java:416)
at com.sun.tools.javac.comp.Resolve.isAccessible(Resolve.java:402)
at com.sun.tools.javac.comp.Resolve.isAccessible(Resolve.java:362)
at com.sun.tools.javac.comp.Resolve.selectBest(Resolve.java:1448)
at com.sun.tools.javac.comp.Resolve.findMethodInScope(Resolve.java:1618)
at com.sun.tools.javac.comp.Resolve.findMethod(Resolve.java:1710)
at com.sun.tools.javac.comp.Resolve.findMethod(Resolve.java:1662)
at com.sun.tools.javac.comp.DeferredAttr$DeferredChecker$2.lookup(DeferredAttr.java:1325)
at com.sun.tools.javac.comp.Resolve.lookupMethod(Resolve.java:3325)
at com.sun.tools.javac.comp.Resolve.lookupMethod(Resolve.java:3310)
at com.sun.tools.javac.comp.DeferredAttr$DeferredChecker.quicklyResolveMethod(DeferredAttr.java:1333)
at com.sun.tools.javac.comp.DeferredAttr$DeferredChecker.visitApply(DeferredAttr.java:1223)
at com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1465)
at com.sun.tools.javac.tree.TreeScanner.scan(TreeScanner.java:49)
at com.sun.tools.javac.comp.DeferredAttr$FilterScanner.scan(DeferredAttr.java:901)
at com.sun.tools.javac.comp.DeferredAttr.isDeferred(DeferredAttr.java:1088)
at com.sun.tools.javac.comp.Attr.attribArgs(Attr.java:701)
at com.sun.tools.javac.comp.Attr.visitApply(Attr.java:1834)
at com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1465)
at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:607)
at com.sun.tools.javac.comp.Attr.attribExpr(Attr.java:656)
at com.sun.tools.javac.comp.Attr.visitExec(Attr.java:1611)
at com.sun.tools.javac.tree.JCTree$JCExpressionStatement.accept(JCTree.java:1296)
at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:607)
at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:676)
at com.sun.tools.javac.comp.Attr.attribStats(Attr.java:692)
at com.sun.tools.javac.comp.Attr.visitBlock(Attr.java:1142)
at com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:909)
at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:607)
at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:676)
at com.sun.tools.javac.comp.Attr.visitForeachLoop(Attr.java:1207)
at com.sun.tools.javac.tree.JCTree$JCEnhancedForLoop.accept(JCTree.java:1035)
at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:607)
at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:676)
at com.sun.tools.javac.comp.Attr.attribStats(Attr.java:692)
at com.sun.tools.javac.comp.Attr.visitBlock(Attr.java:1142)
at com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:909)
at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:607)
at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:676)
at com.sun.tools.javac.comp.Attr.visitMethodDef(Attr.java:1035)
at com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:778)
at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:607)
at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:676)
at com.sun.tools.javac.comp.Attr.attribClassBody(Attr.java:4342)
at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:4252)
at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:4181)
at com.sun.tools.javac.comp.Attr.attrib(Attr.java:4156)
at com.sun.tools.javac.main.JavaCompiler.attribute(JavaCompiler.java:1248)
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 ----------
A.java
======

import java.util.*;

public class A<T extends B & C<T>> extends B {
    private final List<T> tList;
    public A(List<T> tList) {
        this.tList = new LinkedList<>();
        for (T t : tList) {
            // If the following two lines are used instead of the third line
            // this class compiles with jdk8u20 as well
            // final T tClone = t.clone("");
            // this.tList.add(tClone);
            this.tList.add(t.clone(""));
        }
    }

    public T clone(String s) {
        return null;
    }
}


B.java
======

public abstract class B {
    protected B() {
    }
}


C.java
======

public interface C<T> {
    public T clone(String s);
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
I added a comment in A.java how the source can be modified to make it compile with 8u20 as well.