> jshell --enable-preview

| Welcome to JShell -- Version 12-internal
| For an introduction type: /help intro

jshell> String a = `abc`;
Exception in thread "main" java.lang.IllegalArgumentException
at jdk.compiler/com.sun.tools.javac.util.JCDiagnostic.<init>(JCDiagnostic.java:600)
at jdk.compiler/com.sun.tools.javac.util.JCDiagnostic$Factory.create(JCDiagnostic.java:283)
at jdk.compiler/com.sun.tools.javac.util.JCDiagnostic$Factory.error(JCDiagnostic.java:111)
at jdk.compiler/com.sun.tools.javac.util.AbstractLog.error(AbstractLog.java:155)
at jdk.compiler/com.sun.tools.javac.parser.JavaTokenizer.lexError(JavaTokenizer.java:148)
at jdk.compiler/com.sun.tools.javac.parser.JavaTokenizer.checkSourceLevel(JavaTokenizer.java:129)
at jdk.compiler/com.sun.tools.javac.parser.JavaTokenizer.readToken(JavaTokenizer.java:650)
at jdk.compiler/com.sun.tools.javac.parser.Scanner.nextToken(Scanner.java:115)
at jdk.jshell/jdk.jshell.CompletenessAnalyzer$Matched.advance(CompletenessAnalyzer.java:459)
at jdk.jshell/jdk.jshell.CompletenessAnalyzer$Matched.nextCT(CompletenessAnalyzer.java:533)
at jdk.jshell/jdk.jshell.CompletenessAnalyzer$Matched.next(CompletenessAnalyzer.java:467)
at jdk.jshell/jdk.jshell.CompletenessAnalyzer$Parser.nextToken(CompletenessAnalyzer.java:574)
at jdk.jshell/jdk.jshell.CompletenessAnalyzer$Parser.parseDeclaration(CompletenessAnalyzer.java:648)
at jdk.jshell/jdk.jshell.CompletenessAnalyzer$Parser.lambda$disambiguateDeclarationVsExpression$0(CompletenessAnalyzer.java:708)
at jdk.jshell/jdk.jshell.TaskFactory.lambda$parse$6(TaskFactory.java:253)
at jdk.jshell/jdk.jshell.TaskFactory.lambda$runTask$4(TaskFactory.java:213)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskPool.getTask(JavacTaskPool.java:182)
at jdk.jshell/jdk.jshell.TaskFactory.runTask(TaskFactory.java:206)
at jdk.jshell/jdk.jshell.TaskFactory.parse(TaskFactory.java:140)
at jdk.jshell/jdk.jshell.TaskFactory.parse(TaskFactory.java:238)
at jdk.jshell/jdk.jshell.CompletenessAnalyzer.lambda$scan$1(CompletenessAnalyzer.java:90)
at jdk.jshell/jdk.jshell.CompletenessAnalyzer$Parser.disambiguateDeclarationVsExpression(CompletenessAnalyzer.java:688)
at jdk.jshell/jdk.jshell.CompletenessAnalyzer$Parser.parseUnit(CompletenessAnalyzer.java:632)
at jdk.jshell/jdk.jshell.CompletenessAnalyzer.scan(CompletenessAnalyzer.java:91)
at jdk.jshell/jdk.jshell.SourceCodeAnalysisImpl.analyzeCompletion(SourceCodeAnalysisImpl.java:183)
at jdk.jshell/jdk.internal.jshell.tool.ConsoleIOContext$2.isComplete(ConsoleIOContext.java:115)
at jdk.internal.le/jdk.internal.jline.extra.EditingHistory.add(EditingHistory.java:172)
at jdk.internal.le/jdk.internal.jline.console.ConsoleReader.finishBuffer(ConsoleReader.java:738)
at jdk.internal.le/jdk.internal.jline.console.ConsoleReader.accept(ConsoleReader.java:2030)
at jdk.internal.le/jdk.internal.jline.console.ConsoleReader.readLine(ConsoleReader.java:2756)
at jdk.internal.le/jdk.internal.jline.console.ConsoleReader.readLine(ConsoleReader.java:2383)
at jdk.internal.le/jdk.internal.jline.console.ConsoleReader.readLine(ConsoleReader.java:2371)
at jdk.jshell/jdk.internal.jshell.tool.ConsoleIOContext.readLine(ConsoleIOContext.java:142)
at jdk.jshell/jdk.internal.jshell.tool.JShellTool.getInput(JShellTool.java:1261)
at jdk.jshell/jdk.internal.jshell.tool.JShellTool.run(JShellTool.java:1174)
at jdk.jshell/jdk.internal.jshell.tool.JShellTool.start(JShellTool.java:975)
at jdk.jshell/jdk.internal.jshell.tool.JShellToolBuilder.start(JShellToolBuilder.java:254)
at jdk.jshell/jdk.internal.jshell.tool.JShellToolProvider.main(JShellToolProvider.java:120)