Regression: ClassCastException: Type$ErrorType cannot be cast to Type$ArrayType

The following code calling JSR#269/199 API programmatically causes compiler crash in JDK10 b25+. It just prints error as expected when run on JDK10b24 and on earlier builds (including JDK9)

=== full source attached to the bug ==
        JavaCompiler javac = ToolProvider.getSystemJavaCompiler();
        JavaCompiler.CompilationTask task =
            javac.getTask(new OutputStreamWriter(System.err),
            javac.getStandardFileManager(null, null, null),
            null, List.of(), null, List.of(
                new SimpleJavaFileObject(URI.create(""), JavaFileObject.Kind.SOURCE) {
                    @Override public CharSequence getCharContent(boolean ignoreEncodingErrors) {
                        return "class C { void m(Unkn... own) { } }";
                    }
                })
            );
        task.setProcessors(List.of(new AbstractProcessor() {
            @Override public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
                return false;
            }
        }));
        task.call();
=============================

JDK10b25+:
-----------------------------------
An exception has occurred in the compiler (10-ea). Please file a bug against the Java compiler via the Java bug reporting page (http://bugreport.java.com) after checking the Bug Database (http://bugs.java.com) for duplicates. Include your program and the following diagnostic in your report. Thank you.
java.lang.ClassCastException: jdk.compiler/com.sun.tools.javac.code.Type$ErrorType cannot be cast to jdk.compiler/com.sun.tools.javac.code.Type$ArrayType
at jdk.compiler/com.sun.tools.javac.comp.MemberEnter.visitVarDef(MemberEnter.java:278)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCVariableDecl.accept(JCTree.java:956)
at jdk.compiler/com.sun.tools.javac.comp.MemberEnter.memberEnter(MemberEnter.java:162)
at jdk.compiler/com.sun.tools.javac.comp.MemberEnter.signature(MemberEnter.java:110)
at jdk.compiler/com.sun.tools.javac.comp.MemberEnter.visitMethodDef(MemberEnter.java:192)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:866)
at jdk.compiler/com.sun.tools.javac.comp.MemberEnter.memberEnter(MemberEnter.java:162)
at jdk.compiler/com.sun.tools.javac.comp.MemberEnter.memberEnter(MemberEnter.java:174)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$MembersPhase.finishClass(TypeEnter.java:955)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$MembersPhase.runPhase(TypeEnter.java:939)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$Phase.doCompleteEnvs(TypeEnter.java:279)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$MembersPhase.doCompleteEnvs(TypeEnter.java:874)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$Phase.completeEnvs(TypeEnter.java:248)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$Phase.completeEnvs(TypeEnter.java:263)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$Phase.completeEnvs(TypeEnter.java:263)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$Phase.completeEnvs(TypeEnter.java:263)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter.complete(TypeEnter.java:197)
at jdk.compiler/com.sun.tools.javac.code.Symbol.complete(Symbol.java:633)
at jdk.compiler/com.sun.tools.javac.code.Symbol$ClassSymbol.complete(Symbol.java:1308)
at jdk.compiler/com.sun.tools.javac.comp.Enter.complete(Enter.java:577)
at jdk.compiler/com.sun.tools.javac.comp.Enter.main(Enter.java:554)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.enterTrees(JavaCompiler.java:1057)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:928)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.lambda$doCall$0(JavacTaskImpl.java:100)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.handleExceptions(JavacTaskImpl.java:142)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.doCall(JavacTaskImpl.java:96)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.call(JavacTaskImpl.java:90)
at temp.Temp.main(Temp.java:35)
-----------------------------------

JDK10b24 and below:
-----------------------------------
warning: No SupportedSourceVersion annotation found on temp.Temp$2, returning RELEASE_6.
warning: Supported source version 'RELEASE_6' from annotation processor 'temp.Temp$2' less than -source '1.10'
warning: No SupportedAnnotationTypes annotation found on temp.Temp$2, returning an empty set.
:1: error: cannot find symbol
class C { void m(Unkn... own) { } }
                 ^
  symbol: class Unkn
  location: class C
1 error
3 warnings
-----------------------------------