Use identical in token operators.

pkg/front_end/lib/src/fasta/scanner/token.dart

Index: pkg/front_end/lib/src/fasta/scanner/token.dart
diff --git a/pkg/front_end/lib/src/fasta/scanner/token.dart b/pkg/front_end/lib/src/fasta/scanner/token.dart
index 8a7222867abbf5ff0cb2a473df3b25359ee359d0..7bded75413d13b06a90a9bf0681a3c374a5b9b6e 100644
--- a/pkg/front_end/lib/src/fasta/scanner/token.dart
+++ b/pkg/front_end/lib/src/fasta/scanner/token.dart
@@ -350,27 +350,27 @@ bool isUserDefinableOperator(String value) {
       isUnaryOperator(value);
 }
 
-bool isUnaryOperator(String value) => value == '~';
+bool isUnaryOperator(String value) => identical(value, "~");
 
 bool isBinaryOperator(String value) {
-  return value == '==' ||
-      value == '[]' ||
-      value == '*' ||
-      value == '/' ||
-      value == '%' ||
-      value == '~/' ||
-      value == '+' ||
-      value == '<<' ||
-      value == '>>' ||
-      value == '>=' ||
-      value == '>' ||
-      value == '<=' ||
-      value == '<' ||
-      value == '&' ||
-      value == '^' ||
-      value == '|';
+  return identical(value, "==") ||
+      identical(value, "[]") ||
+      identical(value, "*") ||
+      identical(value, "/") ||
+      identical(value, "%") ||
+      identical(value, "~/") ||
+      identical(value, "+") ||
+      identical(value, "<<") ||
+      identical(value, ">>") ||
+      identical(value, ">=") ||
+      identical(value, ">") ||
+      identical(value, "<=") ||
+      identical(value, "<") ||
+      identical(value, "&") ||
+      identical(value, "^") ||
+      identical(value, "|");
 }
 
-bool isTernaryOperator(String value) => value == '[]=';
+bool isTernaryOperator(String value) => identical(value, "[]=");
 
-bool isMinusOperator(String value) => value == '-';
+bool isMinusOperator(String value) => identical(value, "-");