Complain about bad operator parameters.

pkg/front_end/lib/src/fasta/operator.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library fasta.operators;
 
 /// The user-definable operators in Dart.
 ///
 /// The names have been chosen to represent their normal semantic meaning.
 enum Operator {
@@ skipping 81 matching lines @@
       return ">>";
     case Operator.subtract:
       return "-";
     case Operator.truncatingDivide:
       return "~/";
     case Operator.unaryMinus:
       return "unary-";
   }
   return null;
 }
+
+int operatorRequiredArgumentCount(Operator operator) {
+  switch (operator) {
+    case Operator.add:

[karlklose, 2017/03/29 10:12:01]

Consider combining the cases for operators with the same arity.

[ahe, 2017/03/29 10:55:00]

Done.

+      return 1;
+    case Operator.bitwiseAnd:
+      return 1;
+    case Operator.bitwiseNot:
+      return 0;
+    case Operator.bitwiseOr:
+      return 1;
+    case Operator.bitwiseXor:
+      return 1;
+    case Operator.divide:
+      return 1;
+    case Operator.equals:
+      return 1;
+    case Operator.greaterThan:
+      return 1;
+    case Operator.greaterThanEquals:
+      return 1;
+    case Operator.indexGet:
+      return 1;
+    case Operator.indexSet:
+      return 2;
+    case Operator.leftShift:
+      return 1;
+    case Operator.lessThan:
+      return 1;
+    case Operator.lessThanEquals:
+      return 1;
+    case Operator.modulo:
+      return 1;
+    case Operator.multiply:
+      return 1;
+    case Operator.rightShift:
+      return 1;
+    case Operator.subtract:
+      return 1;
+    case Operator.truncatingDivide:
+      return 1;
+    case Operator.unaryMinus:
+      return 0;
+  }
+  return -1;

[karlklose, 2017/03/29 10:12:01]

Should this be an internal error?

[ahe, 2017/03/29 10:55:00]

If feel its sufficient with the warnings you get from missed cases.

+}