Lib.rs

Semantic analysis: scope building and validation.

Signature files (.sig): When .sig files are provided (e.g. stdlib), they are parsed with the signature grammar, then type expressions in each function/global declaration are turned into Type via parse_type_expr and seeded into the root scope. The type checker uses these for inference (e.g. call return types, global variable types). Use analyze_with_signatures(program_root, signature_roots) so that built-in names resolve and types are inferred from the .sig definitions.