Do not overwrite values on plurals/genders with the results of constant evaluation

pkg/intl/test/message_extraction/sample_with_messages.dart

Index: pkg/intl/test/message_extraction/sample_with_messages.dart
diff --git a/pkg/intl/test/message_extraction/sample_with_messages.dart b/pkg/intl/test/message_extraction/sample_with_messages.dart
index e1a9ac37d55372897158ab22d9e7ef9be45c1a5d..8d9d93422fe1475714853c5fdad9e7d5f2e9a052 100644
--- a/pkg/intl/test/message_extraction/sample_with_messages.dart
+++ b/pkg/intl/test/message_extraction/sample_with_messages.dart
@@ -73,6 +73,13 @@ outerPlural(n) => Intl.plural(n, zero: 'none', one: 'one', other: 'some',
 outerGender(g) => Intl.gender(g, male: 'm', female: 'f', other: 'o',
     name: 'outerGender', desc: 'A gender with no enclosing message', args: [g]);
 
+pluralThatFailsParsing(noOfThings) => Intl.plural(noOfThings,
+    one: "1 thing:",
+    other: "$noOfThings things:",
+    name: "pluralThatFailsParsing",
+    args: [noOfThings],
+    desc: "How many things are there?");
+
 // A standalone gender message where we don't provide name or args. This should
 // be rejected by validation code.
 invalidOuterGender(g) => Intl.gender(g, other: 'o');
@@ -171,6 +178,8 @@ printStuff(Intl locale) {
     printOut(outerSelect("EUR", 5));
     printOut(nestedSelect("CDN", 1));
     printOut(nestedSelect("CDN", 2));
+    printOut(pluralThatFailsParsing(1));
+    printOut(pluralThatFailsParsing(2));
   });
 }