diff --git a/pano/function.py b/pano/function.py
index 608a21ae..5960c969 100644
--- a/pano/function.py
+++ b/pano/function.py
@@ -83,15 +83,13 @@ def __init__(self, hash, trace):
 
     def cleanup_masks(self, trace):
         def rem_masks(exp):
-            if m := match(exp, ("bool", ("cd", ":idx"))):
+            if m := match(exp, ("bool", ("cd", ":int:idx"))):
                 idx = m.idx
-                assert type(idx) == int
                 if idx in self.params and self.params[idx][0] == "bool":
                     return ("cd", idx)
 
-            elif m := match(exp, ("mask_shl", ":size", 0, 0, ("cd", ":idx"))):
+            elif m := match(exp, ("mask_shl", ":size", 0, 0, ("cd", ":int:idx"))):
                 size, idx = m.size, m.idx
-                assert type(idx) == int
                 if idx in self.params:
                     kind = self.params[idx][0]
                     def_size = type_to_mask(kind)
diff --git a/pano/matcher.py b/pano/matcher.py
index 97896c0f..5fbe0535 100644
--- a/pano/matcher.py
+++ b/pano/matcher.py
@@ -1,4 +1,5 @@
 import copy
+import builtins
 import logging
 
 logger = logging.getLogger(__name__)
@@ -47,6 +48,10 @@ def _match_helper(expression, pattern, match):
 
     if isinstance(pattern, str) and pattern.startswith(":"):
         attr = pattern[1:]
+        if ":" in attr:
+            type_name, attr = attr.split(":")
+            if not isinstance(expression, getattr(builtins, type_name)):
+                raise NoMatch(expression, pattern)
         if hasattr(match, attr):
             if getattr(match, attr) == expression:
                 return
@@ -89,6 +94,12 @@ def match(expression, pattern):
     2
     >>> bool(match((1, 2, 3, 4), (tuple, ':two', ...)))
     False
+    >>> bool(match((1, 2, 3, 4), (int, ':int:two', ...)))
+    True
+    >>> bool(match((1, "two", 3, 4), (int, ':int:two', ...)))
+    False
+    >>> match(("one", "two", 3, 4), (str, ':str:two', ...)).two
+    'two'
     """
     m = Match()
     try: