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Phase 5 Self-Hosting Preparation

Phase 5 prepared Hydrogen to write its own compiler incrementally. It did not replace the C++ bootstrap compiler.

Delivered Prototype​

The Phase 5 proof workspace lives in the compiler repo at samples/self_hosting:

  • Hydrogen.Compiler.Core provides source text, text spans, locations, and diagnostics.
  • Hydrogen.Compiler.Syntax provides syntax kinds, syntax tokens, syntax nodes, syntax trees, a lexer, and a parser.
  • Hydrogen.Compiler.Cli exposes tokens <file> and parse <file>.
  • Hydrogen.Compiler.Tests validates the prototype from Hydrogen code.

The parser prototype is syntax-only. It handles usings, namespaces, classes, structs, interfaces, enums, members, parameters, blocks, statements, and core expressions, but it does not bind, type-check, lower IR, emit code, or self-compile.

Bootstrap Compiler Contract​

The trusted C++ compiler still owns the real pipeline:

  • lexing
  • parsing
  • semantic model construction
  • binding and type checking
  • bound IR
  • interpreter execution
  • C backend emission
  • runtime support

The Hydrogen frontend mirrored the lexer/parser side first because it was the safest path into self-hosting. Phase 6 now uses these libraries as the foundation for binding, typed IR, native backend integration, and eventually self-compilation.

Proof Commands​

./build/hy build samples/self_hosting/Hydrogen.Compiler.hyproj
./build/hy test samples/self_hosting/Hydrogen.Compiler.hyproj
./build/hy run samples/self_hosting/Hydrogen.Compiler.Cli/Hydrogen.Compiler.Cli.hyproj -- tokens tests/hello_world.hy
./build/hy run samples/self_hosting/Hydrogen.Compiler.Cli/Hydrogen.Compiler.Cli.hyproj -- parse tests/hello_world.hy

Phase 5 is complete at prototype scope when the workspace builds, tests, format-checks, check-runs, and matches golden token/parse fixtures.