Support C#-like named arguments.

Author: webbju

ServerCodeExciserTest/AngelscriptSyntaxTests.cs

@@ -31,6 +31,18 @@ public void Namespace(string @namespace)
             new UnrealAngelscriptSimpleVisitor(script).VisitChildren(parser.script());
         }
 
+        [TestMethod]
+        public void NamedArgumentsFunctionCall()
+        {
+            var script = "void Func(bool Arg1 = false, int Arg2 = 0) {}\r\nvoid main() { Func(Arg2: 1, Arg1: true); }\r\n";
+            var lexer = new UnrealAngelscriptLexer(new AntlrInputStream(script));
+            var tokenStream = new CommonTokenStream(lexer);
+            var parser = new UnrealAngelscriptParser(tokenStream);
+            parser.RemoveErrorListeners();
+            parser.AddErrorListener(new ThrowingErrorListener());
+            new UnrealAngelscriptSimpleVisitor(script).VisitChildren(parser.script());
+        }
+
         [TestMethod]
         [DataRow("")]
         [DataRow("final")]
@@ -40,7 +52,7 @@ public void Namespace(string @namespace)
         [DataRow("accept_temporary_this")] // UnrealAngelscript
         public void FunctionModifier(string modifier)
         {
-            var script = $"protected bool CanActivate_Client() {modifier}\r\n{{\r\nreturn true;\r\n}}";
+            var script = $"protected bool Func() {modifier}\r\n{{\r\nreturn true;\r\n}}";
             var lexer = new UnrealAngelscriptLexer(new AntlrInputStream(script));
             var tokenStream = new CommonTokenStream(lexer);
             var parser = new UnrealAngelscriptParser(tokenStream);

UnrealAngelscriptParser/Grammar/UnrealAngelscriptParser.g4

@@ -89,6 +89,7 @@ qualifiedId: nestedNameSpecifier unqualifiedId;
 nestedNameSpecifier:
 	(theTypeName | namespaceName | decltypeSpecifier)? Doublecolon
 	| nestedNameSpecifier Identifier Doublecolon;
+
 lambdaExpression:
 	lambdaIntroducer lambdaDeclarator? compoundStatement;
 
@@ -217,6 +218,7 @@ assignmentOperator:
 expression: assignmentExpression (Comma assignmentExpression)*;
 
 constantExpression: conditionalExpression;
+
 /*Statements*/
 
 statement:
@@ -468,7 +470,11 @@ braceOrEqualInitializer:
 	Assign initializerClause
 	| bracedInitList;
 
-initializerClause: assignmentExpression | bracedInitList;
+// Angelscript supports C#-like named arguments.
+// https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/named-and-optional-arguments
+initializerClause:
+    (Identifier Colon)? assignmentExpression
+    | bracedInitList;
 
 initializerList:
 	initializerClause (Comma initializerClause)* Comma?; // I *really* don't like that trailing commas are a thing in AS...