Remove number from operator mismatch message.

pkg/front_end/lib/src/fasta/source/outline_builder.dart

Index: pkg/front_end/lib/src/fasta/source/outline_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/source/outline_builder.dart b/pkg/front_end/lib/src/fasta/source/outline_builder.dart
index ca62f0ebec0f25009056b5433bf9af361220789d..1c08f6e5ea7b4be4dbcd634203ad1bad3a20727d 100644
--- a/pkg/front_end/lib/src/fasta/source/outline_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/outline_builder.dart
@@ -20,7 +20,9 @@ import '../fasta_codes.dart'
         messageTypedefNotFunction,
         templateDuplicatedParameterName,
         templateDuplicatedParameterNameCause,
-        templateOperatorParameterMismatch;
+        templateOperatorParameterMismatch0,
+        templateOperatorParameterMismatch1,
+        templateOperatorParameterMismatch2;
 
 import '../modifier.dart' show abstractMask, externalMask, Modifier;
 
@@ -382,10 +384,25 @@ class OutlineBuilder extends UnhandledListener {
       kind = ProcedureKind.Operator;
       int requiredArgumentCount = operatorRequiredArgumentCount(nameOrOperator);
       if ((formals?.length ?? 0) != requiredArgumentCount) {
-        addCompileTimeError(
-            templateOperatorParameterMismatch.withArguments(
-                name, requiredArgumentCount),
-            charOffset);
+        var template;
+        switch (requiredArgumentCount) {
+          case 0:
+            template = templateOperatorParameterMismatch0;
+            break;
+
+          case 1:
+            template = templateOperatorParameterMismatch1;
+            break;
+
+          case 2:
+            template = templateOperatorParameterMismatch2;

[Johnni Winther, 2017/07/13 11:23:39]

How do you handle `operator -(a, b)` ? It shouldn't use
`templateOperatorParameterMismatch1` because it must have either 0 or 1
parameters.

[ahe, 2017/07/13 11:32:19]

Good point.

+            break;
+
+          default:
+            unhandled("$requiredArgumentCount", "operatorRequiredArgumentCount",
+                charOffset, uri);
+        }
+        addCompileTimeError(template.withArguments(name), charOffset);
       } else {
         if (formals != null) {
           for (FormalParameterBuilder formal in formals) {