fixup! feat: introduce UIntNode interface, used within DAG-CBOR codec

codec/dagcbor/roundtrip_test.go

@@ -161,10 +161,10 @@ func TestInts(t *testing.T) {
 				qt.Assert(t, ii, qt.Equals, int64(td.intValue))
 			}
 
-			// if it's a positive number, we should be able to access it as a UintNode
-			// and be able to access the full int64 range
+			// if the number is outside of the positive int64 range, we should be able
+			// to access it as a UintNode and be able to access the full int64 range
 			uin, ok := n.(datamodel.UintNode)
-			if td.intValue < 0 {
+			if td.value <= math.MaxInt64 {
 				qt.Assert(t, ok, qt.IsFalse)
 			} else {
 				qt.Assert(t, ok, qt.IsTrue)

codec/dagcbor/unmarshal.go

@@ -276,7 +276,12 @@ func unmarshal2(na datamodel.NodeAssembler, tokSrc shared.TokenSource, tk *tok.T
 		if *gas < 0 {
 			return ErrAllocationBudgetExceeded
 		}
-		return na.AssignNode(basicnode.NewUint(tk.Uint))
+		// note that this pushes any overflow errors up the stack when AsInt() may
+		// be called on a UintNode that is too large to cast to an int64
+		if tk.Uint > math.MaxInt64 {
+			return na.AssignNode(basicnode.NewUint(tk.Uint))
+		}
+		return na.AssignInt(int64(tk.Uint))
 	case tok.TFloat64:
 		*gas -= 1
 		if *gas < 0 {