Limitations

Things tix doesn’t support yet, or handles imperfectly.

Language features

with blocks

Nested with blocks resolve names inner-to-outer, matching Nix runtime semantics:

with a; with b;
  # names resolve against b first, then a if b doesn't have the field
  x

If no with scope has the field, a MissingField error is reported.

Literal / singleton types

Tix doesn’t have literal types. "circle" is typed as string, not as the literal "circle". This means you can’t do TypeScript-style discriminated unions:

# tix sees this as { type: string, radius: int } | { type: string, width: int }
# not { type: "circle", ... } | { type: "rect", ... }

Enum option types in generated NixOS stubs also become string for this reason.

Dynamic field access

Dynamic attrset field access (x.${name}) uses a general dynamic field type but can’t track which specific field is being accessed.

Type narrowing

Narrowing works well for most common patterns (see Type System), but has some gaps:

• Structural predicates (isAttrs, isList, isFunction) only narrow in the then-branch. The else-branch doesn’t exclude these types.
• Multi-element attrpaths: x ? a.b.c doesn’t narrow — only single-key x ? field works.
• Value equality: if x == "foo" doesn’t narrow x to the literal "foo" (no literal types).
• Overloaded function annotations: intersection-type annotations (e.g. (int -> int) & (string -> string)) are trusted, not verified per-branch.
• Recursive narrowing: using isFunction x in one branch and recursing from another can cause false positives because both branches share the same type variable.

Cross-file inference

• Imports without stubs are inferred as any (the top type). For precise cross-file types, use [project] analyze in tix.toml or write .tix stubs.
• Overloaded operators (like + with polymorphic arguments) don’t survive file boundaries. If a generic function using + is imported from another file, the overload may not resolve correctly.

Recursive attrsets

rec { ... } works but types that refer to themselves can produce verbose output in some cases.

Stubs

• The built-in lib stubs cover common functions but not all of nixpkgs lib. Unstubbed functions get a fresh type variable (no error, just no type info).
• Home Manager flake mode stub generation is less tested than NixOS.
• lib function stubs are curated from noogle.dev data — there’s no auto-generation from nixpkgs lib source yet.