Fix the parser, make the function name optional.

src/syntax/pretty.rs

@@ -33,7 +33,11 @@ where
             TopLevel::Function(name, arg_names, body) => allocator
                 .text("function")
                 .append(allocator.space())
-                .append(allocator.text(name.to_string()))
+                .append(
+                    name.as_ref()
+                        .map(|x| allocator.text(x.to_string()))
+                        .unwrap_or_else(|| allocator.nil()),
+                )
                 .append(
                     allocator
                         .intersperse(