Stage-1 self-hosting roadmap
The compiler is a Java seed, not self-hosted. The Sprig frontend probe in examples/stage1_frontend_probe/frontend.spr reads UTF-8 through HostFiles, lexes tokens/layout, parses bindings, arithmetic, printing, if blocks and typed function declarations, records spans/scopes and prints variant ASTs through exhaustive visitors. tests/bootstrap checks golden fixtures, malformed input, duplicate parameters and added-case exhaustiveness. Calls, full return-type checking and signature recovery remain outside this subset probe.
tests/visitor/ast_visitor.spr and mini_pipeline.spr are smaller feasibility slices. None constitutes a stage-1 compiler.
Incremental path
- Keep stage-0 golden programs and independent diagnostics/output as the oracle.
- Build explicit UTF-8/source-span, Unicode scanning, builder and collection utilities; HostFiles is the existing platform boundary, not a language intrinsic.
- Expand the Sprig lexer/parser and compare token/AST fixtures with stage-0.
- Add a checker subset, deterministic module/build driver and structured diagnostics.
- Emit Java for the subset, then compare diagnostics/output with stage-0.
- Rebuild stage-1 with itself and pass the same acceptance corpus before claiming self-hosting.
Remaining engineering work
Compiler-grade source abstractions, Unicode iteration, efficient text assembly, complete symbol/collection utilities, module discovery and recovery are incomplete. Named recursive visitors work; single-expression lambdas and var plus if provide current workarounds. No new syntax is justified without a measured problem. User generics and file host services already exist, but a complete frontend and backend still require substantial implementation. See host services.