Diagnostics — Luca UI 1.0 Beta docs

Message shape

One-based locations at the offending declaration — invalid arguments fail at compile time when detectable.

Error at 3:5: Duplicate state 'visits' (first at 2:5)

Copy shape

The catalog wording is frozen and asserted byte-for-byte by the test suite. Any wording change is a breaking change and needs a version note.

A summary — the authoritative frozen strings live in the repository catalog.

Failure families and where each is reported.
Group	Covers
Parse and structure	Empty files, root placement, properties outside components, names, single root, tabs, unterminated comments/strings, bad keys and values, imperative operations
Component validation	Duplicate properties and ids, `id`/`visible`/`disabled`/`label` types, unknown properties on registered components
Blocks	Duplicate `layout`/`style`/`state`/`events`/`transitions`/`theme` blocks, non-entry contents, duplicate entries
State	Literal-only initials, duplicates, scalar values, declared-type agreement, unknown keys, numeric range
Bindings	Undeclared references, resolved locked-property types, resolved `id` uniqueness
Events, navigation, runtime	Unknown targets, undeclared events, non-handler values, navigating back from root, scoping work to unmounted components
Themes	Theme name types and mode vocabulary (`system`, `light`, `dark`)
Seam and files	`.lucu` extension enforcement, unreadable files
Testing harness	Lookups by `id` reuse the unknown-target shape at the resolved root