Architecture

This page sketches the compilation pipeline as it stands at slice 1.

Pipeline

            source bytes (.sd)
                  |
                  v
        +-------------------+      mty-syntax::lex
        |       lexer       |      logos-based
        +-------------------+
                  |  Vec<LexedToken>
                  v
        +-------------------+      mty-syntax::parser
        |      parser       |      hand-rolled RD + Pratt
        +-------------------+
                  |  GreenNode (rowan)
                  v
        +-------------------+      mty-syntax::SyntaxNode
        |       CST         |      lossless concrete tree
        +-------------------+
                  |
                  +--------------+
                  |              v
                  |     +-----------------+      mty-ast
                  |     |  typed AST view |      cast wrappers
                  |     +-----------------+
                  |              |
                  v              v
        +-------------------+   +-------------------+
        |    formatter      |   |   HIR lowering    |   mty-hir
        |  (Wadler/Lindig)  |   |    (LoweringCtx)  |
        +-------------------+   +-------------------+
                  |                       |
                  v                       v
              fmt output            Package + Vec<Diagnostic>

mty-driver chains parser → AST cast → HIR lowering and surfaces the combined diagnostics. mty-cli is the user-facing entry point.

Future stages

The full spec pipeline (spec §24.1) adds:

        HIR -> type/effect/capability check
            -> ownership/borrow check
            -> AIR (agent IR)
            -> MtyIR (Mighty mid-level IR)
            -> optimization
            -> LLVM IR    (native release)
            -> Cranelift  (debug/JIT)
            -> Wasm component (web/edge/plugin)

None of these stages exist yet. They map to slices 3–8 of the roadmap.

Crate dependency graph

mty-cli
   |
   v
mty-driver
   |
   +--> mty-syntax
   +--> mty-ast --> mty-syntax
   +--> mty-hir --> mty-ast, mty-diagnostics
   +--> mty-fmt --> mty-syntax
   +--> mty-diagnostics

No cycles. mty-syntax is the foundation; everything else depends on it directly or transitively.

Errors

Every stage produces typed errors that bubble up as Diagnostic values with stable SD codes. The CLI renders them through ariadne; library callers can render or process them as they wish.

Determinism

The compiler is deterministic. Given the same source, the lexer and parser produce the same GreenNode, the lowerer produces the same HIR with the same arena indices, the formatter produces the same bytes, and the snapshot tests round-trip every example identically across runs.