@tag was not allowed to repeat.

releasenotes.md

@@ -60,6 +60,7 @@
 - Failed to find subscript overloading on optional values.
 - `Socket.get_option` didn't properly call `getsockopt`, and `getsockopt` had an invalid signature.
 - Taking the address of a label would cause a crash. #2430
+- `@tag` was not allowed to repeat.
 
 ### Stdlib changes
 - Add `==` to `Pair`, `Triple` and TzDateTime. Add print to `Pair` and `Triple`.

src/compiler/parse_global.c

@@ -1287,12 +1287,14 @@ static inline bool parse_attribute_list(ParseContext *c, Attr ***attributes_ref,
 				*visibility_ref = visibility = parsed_visibility;
 				continue;
 			}
+			if (attr->attr_kind == ATTRIBUTE_TAG) goto ADD;
 		}
 		const char *name = attr->name;
 		FOREACH(Attr *, other_attr, *attributes_ref)
 		{
 			if (other_attr->name == name) RETURN_PRINT_ERROR_AT(false, attr, "Repeat of attribute '%s' here.", name);
 		}
+ADD:
 		vec_add(*attributes_ref, attr);
 		if (use_comma && !try_consume(c, TOKEN_COMMA)) break;
 	}

test/test_suite/compile_time_introspection/tag_multiple.c3t

@@ -0,0 +1,12 @@
+struct Foo @tag("a", true) @tag("b", false)
+{
+	int a;
+}
+fn void main()
+{
+	Foo x;
+	$assert(Foo.has_tagof("b"));
+	$assert(Foo.has_tagof("a"));
+	$assert(Foo.tagof("a"));
+	$assert(!Foo.tagof("b"));
+}