Accept more labels per switch case.

lib/compiler/implementation/typechecker.dart

Index: lib/compiler/implementation/typechecker.dart
diff --git a/lib/compiler/implementation/typechecker.dart b/lib/compiler/implementation/typechecker.dart
index a5cdb5fa2a98be5d40d941e48e52bad90d9a5ec3..c23455d90d31078adeac1e504cd46e3b0cb6791e 100644
--- a/lib/compiler/implementation/typechecker.dart
+++ b/lib/compiler/implementation/typechecker.dart
@@ -729,6 +729,10 @@ class TypeCheckerVisitor implements Visitor<Type> {
     fail(node);
   }
 
+  visitCaseMatch(CaseMatch node) {
+    fail(node);
+  }
+
   visitTryStatement(TryStatement node) {
     fail(node, 'unimplemented');
   }