diff --git a/go/src/miller/types/mlrval.go b/go/src/miller/types/mlrval.go
index 3687421e1..cd06224af 100644
--- a/go/src/miller/types/mlrval.go
+++ b/go/src/miller/types/mlrval.go
@@ -105,3 +105,18 @@ var TYPE_NAMES = [MT_DIM]string{
 	"array",
 	"map",
 }
+
+// TODO: comment more re typedecls
+type MVTypeMask int
+
+const (
+	MT_TYPE_MASK_STRING MVTypeMask = (1 << MT_STRING) | (1 << MT_VOID)
+	MT_TYPE_MASK_INT               = 1 << MT_INT
+	MT_TYPE_MASK_FLOAT             = 1 << MT_FLOAT
+	MT_TYPE_MASK_NUM               = (1 << MT_INT) | (1 << MT_FLOAT)
+	MT_TYPE_MASK_BOOL              = 1 << MT_BOOL
+	MT_TYPE_MASK_ARRAY             = 1 << MT_ARRAY
+	MT_TYPE_MASK_MAP               = 1 << MT_MAP
+	MT_TYPE_MASK_VAR               = (1 << MT_VOID) | (1 << MT_STRING) | (1 << MT_INT) |
+		(1 << MT_FLOAT) | (1 << MT_BOOL) | (1 << MT_ARRAY) | (1 << MT_MAP)
+)
diff --git a/go/todo.txt b/go/todo.txt
index 00ee8a709..14cd962fe 100644
--- a/go/todo.txt
+++ b/go/todo.txt
@@ -4,14 +4,14 @@ TOP OF LIST:
 * window.mlr, window2.mlr -> doc somewhere
 
 * UDF nexts:
+  o typedecls
+  o is_x and asserting_x
+  o put -s ...
   o take another look at mlr -n and seqgen -- ?
     - rand-walk seqgen-then example
     - mlr -n put -f mand.mlr
   o regexes & associated functions -- necessary or not?
 
-! put -s ...
-! is_x and asserting_x
-! local vars w/ typing; UDFs with typing at parameters & retvals
 * Check for "Options:" in all mappers
 * check for `f.Value` reassigned in all mappers -- reflects true default?
 * UDS