Module check 

Resolution and typechecking, elaborating straight into Core.

Stages 4 and 5 of docs/04-compiler-architecture.md §4.1 — “modules, imports, name binding, hygiene scopes → resolved AST” and “HM + rows + effect rows + capabilities → typed AST” — run as one pass that emits stage 6’s Core directly. §4.2 allows exactly three IRs; a separate resolved-but-untyped tree would be a fourth.

Resolution is hygiene-aware

A reference resolves to a binding when binding.scopes ⊆ reference.scopes, innermost first. That one rule is what makes the macro expander’s work mean something: a binding a macro introduced carries a scope the call site does not have, so the call site cannot see it.

What Phase 1 checks, and what it does not

Checked: HM inference with unification and let-polymorphism, ADTs (union), records (model), nominal newtypes, match exhaustiveness, mandatory annotations on top-level signatures, and the Stream/Signal/fold/durable types of §3.7.

Phase 2 adds §3.2’s effect inference. Every definition gets a row variable before any body is checked; checking a body accumulates the latent row of everything it applies; the variable is then bound to what accumulated. A mere reference to a function performs nothing — only applying one does — which is the difference between inference and Phase 1’s syntactic collection, and the reason fold(apply_event, …) is not itself effectful.

Mutual recursion needs no ordering: f’s row may be bound to a row mentioning g’s variable and vice versa, and Subst::resolve_row computes the least fixed point because a row is a union.

Not checked, and named rather than implied: row polymorphism on records, trait constraints on type variables, and var mutability (a var binding is checked as an ordinary immutable one).

Structs

Checker

Def

Program

A checked module: everything the placement checker, the splitter and the runtime need.

SignalDecl

A top-level signal or stream declaration — the wiring of the program.

Enums

IdentityDecl

Who authenticates a program’s clients, as the program declared it.

Mode

What kind of file is being checked.

Functions

check_module

Check a module that macro expansion has already run over.

check_module_with

Check a module against the interfaces it imports — §3.6’s separate compilation.

is_impl_method

Is this the name of a desugared impl method rather than something a program wrote?