FULL PRODUCT VERSION :
java version "1.8.0_60-ea"
Java(TM) SE Runtime Environment (build 1.8.0_60-ea-b21)
Java HotSpot(TM) 64-Bit Server VM (build 25.60-b21, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Darwin 14.3.0 Darwin Kernel Version 14.3.0: Mon Mar 23 11:59:05 PDT 2015; root:xnu-2782.20.48~5/RELEASE_X86_64 x86_64

A DESCRIPTION OF THE PROBLEM :
When a catch block catches multiple exceptions that implement the same interface and a (redundant) cast to the type of that interface is done within that block, the compiler crashes with the following trace:

Information:Using javac 1.8.0_60-ea to compile java sources
Information:java: An exception has occurred in the compiler (1.8.0_60-ea). Please file a bug at the Java Bug Database (http://bugreport.java.com/bugreport/) after checking the database for duplicates. Include your program and the following diagnostic in your report. Thank you.
Information:java: java.lang.ClassCastException: com.sun.tools.javac.code.Type$UnionClassType cannot be cast to com.sun.tools.javac.code.Type$IntersectionClassType
Information:java: at com.sun.tools.javac.code.Types$8.visitClassType(Types.java:1545)
Information:java: at com.sun.tools.javac.code.Types$8.visitClassType(Types.java:1502)
Information:java: at com.sun.tools.javac.code.Type$ClassType.accept(Type.java:778)
Information:java: at com.sun.tools.javac.code.Types$DefaultTypeVisitor.visit(Types.java:4559)
Information:java: at com.sun.tools.javac.code.Types.isCastable(Types.java:1493)
Information:java: at com.sun.tools.javac.comp.Check.checkCastable(Check.java:568)
Information:java: at com.sun.tools.javac.comp.Check.checkCastable(Check.java:565)
Information:java: at com.sun.tools.javac.comp.Attr.visitTypeCast(Attr.java:3099)
Information:java: at com.sun.tools.javac.tree.JCTree$JCTypeCast.accept(JCTree.java:1814)
Information:java: at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:566)
Information:java: at com.sun.tools.javac.comp.Attr.attribExpr(Attr.java:608)
Information:java: at com.sun.tools.javac.comp.Attr.visitVarDef(Attr.java:1065)
Information:java: at com.sun.tools.javac.tree.JCTree$JCVariableDecl.accept(JCTree.java:852)
Information:java: at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:635)
Information:java: at com.sun.tools.javac.comp.Attr.attribStats(Attr.java:651)
Information:java: at com.sun.tools.javac.comp.Attr.visitBlock(Attr.java:1114)
Information:java: at com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:909)
Information:java: at com.sun.tools.javac.comp.Attr.visitTry(Attr.java:1367)
Information:java: at com.sun.tools.javac.tree.JCTree$JCTry.accept(JCTree.java:1173)
Information:java: at com.sun.tools.javac.comp.Attr.visitMethodDef(Attr.java:1003)
Information:java: at com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:778)
Information:java: at com.sun.tools.javac.comp.Attr.attribClassBody(Attr.java:4341)
Information:java: at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:4249)
Information:java: at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:4178)
Information:java: at com.sun.tools.javac.comp.Attr.attrib(Attr.java:4153)
Information:java: at com.sun.tools.javac.main.JavaCompiler.attribute(JavaCompiler.java:1248)
Information:java: at com.sun.tools.javac.main.JavaCompiler.compile2(JavaCompiler.java:901)
Information:java: at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:860)
Information:java: at com.sun.tools.javac.main.Main.compile(Main.java:523)
Information:java: at com.sun.tools.javac.api.JavacTaskImpl.doCall(JavacTaskImpl.java:129)
Information:java: at com.sun.tools.javac.api.JavacTaskImpl.call(JavacTaskImpl.java:138)
Information:java: at org.jetbrains.jps.javac.JavacMain.compile(JavacMain.java:168)
Information:java: at org.jetbrains.jps.incremental.java.JavaBuilder.compileJava(JavaBuilder.java:382)
Information:java: at org.jetbrains.jps.incremental.java.JavaBuilder.compile(JavaBuilder.java:296)
Information:java: at org.jetbrains.jps.incremental.java.JavaBuilder.doBuild(JavaBuilder.java:204)
Information:java: at org.jetbrains.jps.incremental.java.JavaBuilder.build(JavaBuilder.java:176)
Information:java: at org.jetbrains.jps.incremental.IncProjectBuilder.runModuleLevelBuilders(IncProjectBuilder.java:1196)
Information:java: at org.jetbrains.jps.incremental.IncProjectBuilder.runBuildersForChunk(IncProjectBuilder.java:877)
Information:java: at org.jetbrains.jps.incremental.IncProjectBuilder.buildTargetsChunk(IncProjectBuilder.java:945)
Information:java: at org.jetbrains.jps.incremental.IncProjectBuilder.buildChunkIfAffected(IncProjectBuilder.java:840)
Information:java: at org.jetbrains.jps.incremental.IncProjectBuilder.buildChunks(IncProjectBuilder.java:663)
Information:java: at org.jetbrains.jps.incremental.IncProjectBuilder.runBuild(IncProjectBuilder.java:370)
Information:java: at org.jetbrains.jps.incremental.IncProjectBuilder.build(IncProjectBuilder.java:191)
Information:java: at org.jetbrains.jps.cmdline.BuildRunner.runBuild(BuildRunner.java:137)
Information:java: at org.jetbrains.jps.cmdline.BuildSession.runBuild(BuildSession.java:293)
Information:java: at org.jetbrains.jps.cmdline.BuildSession.run(BuildSession.java:124)
Information:java: at org.jetbrains.jps.cmdline.BuildMain$MyMessageHandler$1.run(BuildMain.java:242)
Information:java: at org.jetbrains.jps.service.impl.SharedThreadPoolImpl$1.run(SharedThreadPoolImpl.java:41)
Information:java: at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
Information:java: at java.util.concurrent.FutureTask.run(FutureTask.java:266)
Information:java: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
Information:java: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
Information:java: at java.lang.Thread.run(Thread.java:745)
Information:java: Errors occurred while compiling module 'sub-war'
Information:01-07-15 09:33 - Compilation completed with 1 error and 0 warnings in 2s 840ms
Error:java: Compilation failed: internal java compiler error

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Minimal example to reproduce the problem.
(Note the similarity with https://bugs.openjdk.java.net/browse/JDK-8071291)

interface A { }
class Exception1 extends Exception implements A { }
class Exception2 extends Exception implements A { }

class Test {
    void test(boolean cond) {
        try {
            if (cond) {
                throw new Exception1();
            } else {
                throw new Exception2();
            }
        }
        catch (Exception1|Exception2 x) {
            A a = (A) x;
        }
    }
}

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I expected the code to be compiled without errors.
ACTUAL -
The compiler crashes and no .class is generated.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Information:Using javac 1.8.0_60-ea to compile java sources
Information:java: An exception has occurred in the compiler (1.8.0_60-ea). Please file a bug at the Java Bug Database (http://bugreport.java.com/bugreport/) after checking the database for duplicates. Include your program and the following diagnostic in your report. Thank you.
Information:java: java.lang.ClassCastException: com.sun.tools.javac.code.Type$UnionClassType cannot be cast to com.sun.tools.javac.code.Type$IntersectionClassType
Information:java: at com.sun.tools.javac.code.Types$8.visitClassType(Types.java:1545)
Information:java: at com.sun.tools.javac.code.Types$8.visitClassType(Types.java:1502)
Information:java: at com.sun.tools.javac.code.Type$ClassType.accept(Type.java:778)
Information:java: at com.sun.tools.javac.code.Types$DefaultTypeVisitor.visit(Types.java:4559)
Information:java: at com.sun.tools.javac.code.Types.isCastable(Types.java:1493)
Information:java: at com.sun.tools.javac.comp.Check.checkCastable(Check.java:568)
Information:java: at com.sun.tools.javac.comp.Check.checkCastable(Check.java:565)
Information:java: at com.sun.tools.javac.comp.Attr.visitTypeCast(Attr.java:3099)
Information:java: at com.sun.tools.javac.tree.JCTree$JCTypeCast.accept(JCTree.java:1814)
Information:java: at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:566)
Information:java: at com.sun.tools.javac.comp.Attr.attribExpr(Attr.java:608)
Information:java: at com.sun.tools.javac.comp.Attr.visitVarDef(Attr.java:1065)
Information:java: at com.sun.tools.javac.tree.JCTree$JCVariableDecl.accept(JCTree.java:852)
Information:java: at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:635)
Information:java: at com.sun.tools.javac.comp.Attr.attribStats(Attr.java:651)
Information:java: at com.sun.tools.javac.comp.Attr.visitBlock(Attr.java:1114)
Information:java: at com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:909)
Information:java: at com.sun.tools.javac.comp.Attr.visitTry(Attr.java:1367)
Information:java: at com.sun.tools.javac.tree.JCTree$JCTry.accept(JCTree.java:1173)
Information:java: at com.sun.tools.javac.comp.Attr.visitMethodDef(Attr.java:1003)
Information:java: at com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:778)
Information:java: at com.sun.tools.javac.comp.Attr.attribClassBody(Attr.java:4341)
Information:java: at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:4249)
Information:java: at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:4178)
Information:java: at com.sun.tools.javac.comp.Attr.attrib(Attr.java:4153)
Information:java: at com.sun.tools.javac.main.JavaCompiler.attribute(JavaCompiler.java:1248)
Information:java: at com.sun.tools.javac.main.JavaCompiler.compile2(JavaCompiler.java:901)
Information:java: at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:860)
Information:java: at com.sun.tools.javac.main.Main.compile(Main.java:523)
Information:java: at com.sun.tools.javac.api.JavacTaskImpl.doCall(JavacTaskImpl.java:129)
Information:java: at com.sun.tools.javac.api.JavacTaskImpl.call(JavacTaskImpl.java:138)
Information:java: at org.jetbrains.jps.javac.JavacMain.compile(JavacMain.java:168)
Information:java: at org.jetbrains.jps.incremental.java.JavaBuilder.compileJava(JavaBuilder.java:382)
Information:java: at org.jetbrains.jps.incremental.java.JavaBuilder.compile(JavaBuilder.java:296)
Information:java: at org.jetbrains.jps.incremental.java.JavaBuilder.doBuild(JavaBuilder.java:204)
Information:java: at org.jetbrains.jps.incremental.java.JavaBuilder.build(JavaBuilder.java:176)
Information:java: at org.jetbrains.jps.incremental.IncProjectBuilder.runModuleLevelBuilders(IncProjectBuilder.java:1196)
Information:java: at org.jetbrains.jps.incremental.IncProjectBuilder.runBuildersForChunk(IncProjectBuilder.java:877)
Information:java: at org.jetbrains.jps.incremental.IncProjectBuilder.buildTargetsChunk(IncProjectBuilder.java:945)
Information:java: at org.jetbrains.jps.incremental.IncProjectBuilder.buildChunkIfAffected(IncProjectBuilder.java:840)
Information:java: at org.jetbrains.jps.incremental.IncProjectBuilder.buildChunks(IncProjectBuilder.java:663)
Information:java: at org.jetbrains.jps.incremental.IncProjectBuilder.runBuild(IncProjectBuilder.java:370)
Information:java: at org.jetbrains.jps.incremental.IncProjectBuilder.build(IncProjectBuilder.java:191)
Information:java: at org.jetbrains.jps.cmdline.BuildRunner.runBuild(BuildRunner.java:137)
Information:java: at org.jetbrains.jps.cmdline.BuildSession.runBuild(BuildSession.java:293)
Information:java: at org.jetbrains.jps.cmdline.BuildSession.run(BuildSession.java:124)
Information:java: at org.jetbrains.jps.cmdline.BuildMain$MyMessageHandler$1.run(BuildMain.java:242)
Information:java: at org.jetbrains.jps.service.impl.SharedThreadPoolImpl$1.run(SharedThreadPoolImpl.java:41)
Information:java: at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
Information:java: at java.util.concurrent.FutureTask.run(FutureTask.java:266)
Information:java: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
Information:java: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
Information:java: at java.lang.Thread.run(Thread.java:745)
Information:java: Errors occurred while compiling module 'sub-war'
Information:01-07-15 09:33 - Compilation completed with 1 error and 0 warnings in 2s 840ms
Error:java: Compilation failed: internal java compiler error

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
interface A { }
class Exception1 extends Exception implements A { }
class Exception2 extends Exception implements A { }

class Test {
    void test(boolean cond) {
        try {
            if (cond) {
                throw new Exception1();
            } else {
                throw new Exception2();
            }
        }
        catch (Exception1|Exception2 x) {
            A a = (A) x;
        }
    }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Avoid the cast.