Added some throwing stubs to parser

Parser.cs

@@ -184,7 +184,7 @@ class Parser
 				Expr elseCase = expression();
 				return new If { Condition = condition, Then = thenCase, Else = elseCase };
 			case TokenType.When:
-				throw new NotImplementedException();
+				throw new NotImplementedException("TODO when");
 		}
 
 		return primary();
@@ -207,6 +207,7 @@ class Parser
 	private Expr primary()
 	{
 		Expr expr = operand();
+
 		if (match(TokenType.Period))
 		{
 			Name? ident = name();
@@ -216,14 +217,17 @@ class Parser
 			}
 			return new Selector { Left = expr, FieldName = ident };
 		}
+
 		if (match(TokenType.LBracket))
 		{
 			throw new NotImplementedException("TODO index");
 		}
+
 		if (match(TokenType.LParen))
 		{
 			throw new NotImplementedException("TODO apply");
 		}
+
 		return expr;
 	}
 
@@ -247,6 +251,35 @@ class Parser
 			return new Grouping { Expression = expr };
 		}
 
+		Expr? expr;
+		if ((expr = record()) != null)
+		{
+			return expr;
+		}
+		if ((expr = variant()) != null)
+		{
+			return expr;
+		}
+		if ((expr = list()) != null)
+		{
+			return expr;
+		}
+
 		throw error(peek(), "Expect expression.");
 	}
+
+	private Expr? list()
+	{
+		throw new NotImplementedException("TODO list");
+	}
+
+	private Expr? variant()
+	{
+		throw new NotImplementedException("TODO variant");
+	}
+
+	private Expr? record()
+	{
+		throw new NotImplementedException("TODO record");
+	}
 }