parser: add incomplete parsing of method functions

src/parser.zig

@@ -390,6 +390,23 @@ pub const Parser = struct {
         errdefer param_list.deinit();
 
         _ = try self.consumeSingle(.Fn);
+
+        if (self.check(.LeftParen)) {
+            _ = try self.consume(.LeftParen);
+
+            var mutable_ref: bool = false;
+            const method_var = try self.consume(.Identifier);
+
+            if (self.check(.Mut)) {
+                _ = try self.consume(.Mut);
+                mutable_ref = true;
+            }
+
+            const method_typ = try self.consume(.Identifier);
+
+            _ = try self.consume(.RightParen);
+        }
+
         const name = try self.consumeSingle(.Identifier);
 
         _ = try self.consumeSingle(.LeftParen);