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Lyth

ADR 0001: Compile to Go source through `go/ast`

Status: Accepted

Context

Section titled “Context”

Lyth must reuse Go’s runtime, toolchain, and ecosystem, produce readable output, and keep exact source positions for diagnostics.

Decision

Section titled “Decision”

Lower the typed Lyth AST directly to go/ast, print with go/printer (gofmt configuration), and build with the official go command. go/ast is the intermediate representation: there is no separate Lyth IR in v0.

Alternatives

Section titled “Alternatives”
  • Emit Go text with a custom writer. Exact position control, but the output is not gofmt-canonical without re-formatting (which loses positions), and injection and precedence bugs become string bugs.
  • Custom IR, then go/ast. Useful for optimizations Lyth does not need yet, and would duplicate go/ast’s statement/expression forms. Can be inserted later between check and lower.
  • Compile to Go SSA or object code. Loses readability, debuggability, and toolchain compatibility. Rejected.

Consequences

Section titled “Consequences”

Output is gofmt-canonical and syntactically valid by construction. Positions come from a print → reparse → lockstep walk (ADR 0005), which also catches lowering bugs. Verified: the printer inserts parentheses for precedence when a ParenExpr is missing, so the walk skips ParenExpr nodes.