REPL crashes when trying to delete match operand in longer statement

[BarkingBad]

Compiler version

3.1.0-RC1

Minimized code

Paste/Type into the REPL following code:

def calculateSum(i: List[Int]): Int =
     i match
         case Nil => 0
         case head :: tail => head + calculateSum(tail)

Now try to move the cursor to i before match and try to remove it using backspace.

Output

Scala REPL crashes with the following stacktrace

     |      iException in thread "main" java.lang.AssertionError: assertion failed
     |  at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:11)
     |  at dotty.tools.dotc.util.Spans$Span$.start$extension(Spans.scala:44)
	at dotty.tools.dotc.parsing.Parsers$Parser.matchClause(Parsers.scala:2114)
	at dotty.tools.dotc.parsing.Parsers$Parser.recur$4(Parsers.scala:955)
	at dotty.tools.dotc.parsing.Parsers$Parser.infixOps(Parsers.scala:964)
	at dotty.tools.dotc.parsing.Parsers$Parser.postfixExprRest(Parsers.scala:2209)
	at dotty.tools.dotc.parsing.Parsers$Parser.postfixExpr(Parsers.scala:2199)
	at dotty.tools.dotc.parsing.Parsers$Parser.expr1(Parsers.scala:2044)
	at dotty.tools.dotc.parsing.Parsers$Parser.expr(Parsers.scala:1937)
	at dotty.tools.dotc.parsing.Parsers$Parser.$init$$$anonfun$5(Parsers.scala:1903)
	at dotty.tools.dotc.parsing.Parsers$Parser.subPart(Parsers.scala:600)
	at dotty.tools.dotc.parsing.Parsers$Parser.subExpr(Parsers.scala:1905)
	at dotty.tools.dotc.parsing.Parsers$Parser.defDefOrDcl(Parsers.scala:3358)
	at dotty.tools.dotc.parsing.Parsers$Parser.defOrDcl(Parsers.scala:3249)
	at dotty.tools.dotc.parsing.Parsers$Parser.localDef(Parsers.scala:3930)
	at dotty.tools.dotc.parsing.Parsers$Parser.blockStatSeq$$anonfun$1(Parsers.scala:3954)
	at dotty.tools.dotc.parsing.Parsers$Parser.checkNoEscapingPlaceholders(Parsers.scala:477)
	at dotty.tools.dotc.parsing.Parsers$Parser.blockStatSeq(Parsers.scala:3960)
	at dotty.tools.dotc.printing.SyntaxHighlighting$.highlight(SyntaxHighlighting.scala:124)
	at dotty.tools.repl.JLineTerminal$Highlighter.highlight(JLineTerminal.scala:80)
	at org.jline.reader.impl.LineReaderImpl.getHighlightedBuffer(LineReaderImpl.java:4071)
	at org.jline.reader.impl.LineReaderImpl.getDisplayedBufferWithPrompts(LineReaderImpl.java:4010)
	at org.jline.reader.impl.LineReaderImpl.redisplay(LineReaderImpl.java:3879)
	at org.jline.reader.impl.LineReaderImpl.doCleanup(LineReaderImpl.java:2566)
	at org.jline.reader.impl.LineReaderImpl.cleanup(LineReaderImpl.java:2557)
	at org.jline.reader.impl.LineReaderImpl.readLine(LineReaderImpl.java:727)
	at org.jline.reader.impl.LineReaderImpl.readLine(LineReaderImpl.java:468)
	at dotty.tools.repl.JLineTerminal.readLine(JLineTerminal.scala:72)
	at dotty.tools.repl.ReplDriver.readLine$1(ReplDriver.scala:140)
	at dotty.tools.repl.ReplDriver.loop$1(ReplDriver.scala:150)
	at dotty.tools.repl.ReplDriver.runUntilQuit$$anonfun$1(ReplDriver.scala:155)
	at dotty.tools.repl.ReplDriver.withRedirectedOutput(ReplDriver.scala:174)
	at dotty.tools.repl.ReplDriver.runUntilQuit(ReplDriver.scala:155)
	at dotty.tools.repl.ReplDriver.tryRunning(ReplDriver.scala:117)
	at dotty.tools.repl.Main$.main(Main.scala:6)
	at dotty.tools.MainGenericRunner$.run$1(MainGenericRunner.scala:137)
	at dotty.tools.MainGenericRunner$.main(MainGenericRunner.scala:175)
	at dotty.tools.MainGenericRunner.main(MainGenericRunner.scala)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at coursier.bootstrap.launcher.a.a(Unknown Source)
	at coursier.bootstrap.launcher.Launcher.main(Unknown Source)

Expectation

I can remove the i and the REPL waits for my final input.

[BarkingBad]

The issue seems to be when there is no identifier before match. If we have a name like list, we can remove any characters as long as one character will exist. After removing the last character, the REPL crashes.