Diagnostics

Every pass emits diagnostics through diagnostics.DiagnosticSink, which renders to plain text, JSON, or SARIF.

Codes

Prefix	Origin
L00xx	Lexer
P00xx	Parser
R00xx	Resolver
T00xx	Typechecker
W00xx	Typechecker warnings

The full catalog (with the source spans that emit each code) lives at docs/design/DIAGNOSTICS.md in the repository.

Wording rules

User-facing messages must not cite the Kotlin Language Specification. Phrase the problem and the fix in user-actionable terms:

Prefer	Avoid
`f` cannot be both `private` and `open`	`f` cannot be both `private` and `open` (spec §5.4)
expected;after import, found}	import declarations end with a newline per §10.2

Spec citations belong in the source comment above the diagnostic emitter, never in the message text.

Rendering formats

klio check src/Main.kt --format plain   # default, terminal-friendly
klio check src/Main.kt --format json    # structured for editors
klio check src/Main.kt --format sarif   # CI / GitHub annotations

The JSON shape is stable for tool integration; the plain renderer is the default human form and the one parity tests assert against.