Tya v0.54 Specification

Status: shipped. The tya version constant is 0.54.0. v0.54 routes Parser / Codegen / Runner errors through the same structured diag.Diagnostic channel used by Lexer and Checker, adds multi-error parsing, and surfaces did-you-mean suggestions for undefined names. The language surface is unchanged from v0.53.

Theme

Tya’s compiler stages have historically emitted diagnostics in two flavours: diag.Diagnostic for lexer + checker, and free-form fmt.Errorf strings for parser, codegen, and runner. v0.54 finishes the migration so every stage speaks the same structured shape. The visible payoff:

Every error has a stable [TYA-EXXXX] code.
The CLI renders rich blocks (banner, source pointer, code).
The LSP receives every parse error in one pass (no more one-error-and-stop on didOpen / didChange).
Undefined names get a did you mean "…"? hint when a close candidate exists.

New diagnostic codes

Parser (TYA-E0100-0299):

Code	Bucket
`TYA-E0100`	Expected token / syntax (open-of-block, bracket, keyword)
`TYA-E0101`	Expected indented block
`TYA-E0102`	Unexpected token
`TYA-E0120`	Position constraint (return / break / continue / module / outside scope)
`TYA-E0140`	Reserved name / keyword used as identifier
`TYA-E0141`	Deprecated or unsupported syntax
`TYA-E0160`	Pattern / multi-assignment syntax
`TYA-E0180`	Expected expression

Codegen (TYA-E0600-0699):

Code	Meaning
`TYA-E0601`	Unsupported assignment target
`TYA-E0602`	Unsupported statement or expression
`TYA-E0603`	Unsupported match pattern
`TYA-E0604`	`try` outside function body
`TYA-E0605`	Non-tuple multi-assignment
`TYA-E0606`	Destructuring target is not an Ident

Runner (TYA-E0800-0899):

Code	Meaning
`TYA-E0840`	Invalid Tya filename
`TYA-E0850-0855`	(existing) module / package validation
`TYA-E0856`	Entry file redefines its module
`TYA-E0857`	Import name conflict
`TYA-E0858`	Undefined variable (with optional did-you-mean)

Multi-error parsing

The parser now keeps parsing after a statement-level failure. When block() or program() encounters an error, the diagnostic is recorded on the parser’s accumulator, skipToNextStmt() advances to the next plausible statement boundary (NEWLINE / DEDENT / EOF), and parsing resumes. When Parse() returns it flushes the accumulator into *parser.ParserError{Diags: []diag.Diagnostic}.

$ tya check three_top_level_returns.tya
-- RETURN MUST BE INSIDE A FUNCTION ---- three_top_level_returns.tya:1:1
…
(TYA-E0120)

-- BREAK MUST BE INSIDE A LOOP -------- three_top_level_returns.tya:2:1
…
(TYA-E0120)

-- CONTINUE MUST BE INSIDE A LOOP ----- three_top_level_returns.tya:3:1
…
(TYA-E0120)

Found 3 error(s), 0 warning(s).

Recovery is statement-level only — expression-level recovery is queued for v0.55+ (see “Out of scope”).

Did-you-mean suggestions

Undefined-name errors (TYA-E0858 in runner, the same surface in checker) pass the offending name plus the candidate pool (builtin function names + the current scope’s defined names) through util.Suggest. Suggestions whose Levenshtein distance to the queried name is ≤ 2 are appended to the diagnostic as a hint:

typo.tya:2:7: undefined variable strng; did you mean "string"?

At most three candidates are listed. When no candidate qualifies, no hint is emitted (the original error stands unchanged).

util.Suggest lives at internal/util/strdist.go and is reused by runner and checker; future stages can call the same helper.

LSP and CLI integration

internal/lsp/diagnostics.go::DiagnosticsFor now errors.As- unwraps *parser.ParserError and emits every contained diagnostic via publishDiagnostics. Single-error fallback path is preserved for non-parser errors.
cmd/tya/main.go::printDiagnostic adds parser / runner / codegen unwrap branches so the same rich-render path is used for every stage.

Out of scope (v0.55+)

Parser signature change (Parse() → (*Program, []Diag, error)) for symmetry with lexer.LexWithComments.
Expression-level recovery (currently statement-level only).
LSP code actions for did-you-mean fixes (apply the suggestion with a single click).
Codegen / Runner signature change to also return []Diag slices.

Compatibility

Language surface: unchanged from v0.53.
tya.toml schema: unchanged.
CLI: every existing subcommand keeps its v0.53 behaviour. Diagnostic output gains the [TYA-EXXXX] prefix and the banner-style render for stages that previously emitted only line:col: msg.
Existing tests that grep substrings like "undefined variable" continue to match.

Tests

tests/testdata/v54_diag/ adds two testscript fixtures — multi_error.txtar (three top-level position violations in one pass) and did_you_mean.txtar (typo with hint). All pre-existing tests stay green; the parser unit tests keep their legacy substring expectations because *ParserError.Error() preserves the line:col: msg near "tok" format on Error().