feat: Extracting the type for arguments to arb files

lib/extract_messages.dart

@@ -376,9 +376,10 @@ class MessageFindingVisitor extends GeneralizingAstVisitor {
     message.sourcePosition = node.offset;
     message.endPosition = node.end;
     message.arguments = parameters?.parameters
-            .map((x) => x.name?.lexeme)
-            .where((element) => element != null)
-            .cast<String>()
+            .where((element) => element.name?.lexeme != null)
+            .map((x) => x is SimpleFormalParameter ?
+               MessageArgument(type: x.type?.toString(), name: x.name!.lexeme) :
+               MessageArgument(name: x.name!.lexeme))
             .toList() ??
         [];
     var arguments = node.argumentList.arguments;
@@ -543,7 +544,7 @@ class InterpolationVisitor extends SimpleAstVisitor {
   }
 
   void handleSimpleInterpolation(InterpolationExpression node) {
-    var index = arguments.indexOf(node.expression.toString());
+    var index = arguments.indexWhere((x) => x.name == node.expression.toString());
     if (index == -1) {
       throw new IntlMessageExtractionException(
           "Cannot find argument ${node.expression}");

lib/src/arb_generation.dart

@@ -45,20 +45,23 @@ Map arbMetadata(MainMessage message) {
   var placeholders = {};
   var placeholderNames = [];
   for (var arg in message.arguments) {
-    placeholderNames.add(arg);
+    placeholderNames.add(arg.name);
     addArgumentFor(message, arg, placeholders);
   }
   out["placeholders_order"] = placeholderNames;
   out["placeholders"] = placeholders;
   return out;
 }
 
-void addArgumentFor(MainMessage message, String arg, Map result) {
+void addArgumentFor(MainMessage message, MessageArgument arg, Map result) {
   var extraInfo = {};
-  if (message.examples.isNotEmpty && message.examples[arg] != null) {
-    extraInfo["example"] = message.examples[arg];
+  if (arg.type != null) {
+    extraInfo["type"] = arg.type;
   }
-  result[arg] = extraInfo;
+  if (message.examples.isNotEmpty && message.examples[arg.name] != null) {
+    extraInfo["example"] = message.examples[arg.name];
+  }
+  result[arg.name] = extraInfo;
 }
 
 /// Return a version of the message string with with ICU parameters "{variable}"

lib/src/intl_message.dart

@@ -482,7 +482,7 @@ class MainMessage extends ComplexMessage {
   String? id;
 
   /// The arguments list from the Intl.message call.
-  List<String> arguments = [];
+  List<MessageArgument> arguments = [];
 
   /// The locale argument from the Intl.message call
   String? locale;
@@ -977,3 +977,13 @@ class IntlMessageExtractionException implements Exception {
 
   String toString() => "IntlMessageExtractionException: $message";
 }
+
+// An argument for a message. Arguments might have a type and must have a name.
+class MessageArgument {
+  final String? type;
+  final String name;
+
+  const MessageArgument({this.type, required this.name});
+
+  String toString() => "$type $name";
+}