Type-check struct/enum definitions and struct literals #50

Merged

jacksonopp merged 5 commits from us4/type-check-struct-enum into main

2026-09-03 01:45:11 +00:00

jacksonopp commented

2026-09-03 01:40:31 +00:00

Owner

Closes #4.

Summary

TyKind::Struct/TyKind::Enum, nominal (carry a name: Symbol), with
enum variant payloads staying Option<Ty> to distinguish a no-payload
variant from a resolution failure.
check_expr gains a name_hint: Option<Symbol> parameter, populated
only by check_let, so struct { ... }/enum { ... } declarations can
be named without needing their own syntax for it (per let X = struct {...}).
A None hint reports NamelessStruct/NamelessEnum.
check_struct_literal checks Expr::StructLiteral against its declared
struct: name-based (not positional) field matching over the union of
literal/declared field names, catching unknown fields
(StructFieldNotDefined), missing required fields (MissingStructType),
and field type mismatches (StructFieldMismatch) in one pass. A literal
against an undeclared or non-struct name reports NoStruct.
Enum variant construction/matching (Reserved(slot), match) is
explicitly out of scope — no EnumLiteral HIR node exists; that's
Expr::Call/Expr::Match checking, later work.
check_expr's match arms extracted into their own functions
(check_ident/check_block/check_fn/check_call/check_struct/
check_enum/check_struct_literal) to keep it readable as more
constructs are added.
docs/type-checker-design.md gets a new ## Issue #4 section
documenting these decisions.

Test plan

cargo test -p twill-check — 123 tests passing, including 6 new
tests each for struct/enum declaration checking and struct-literal
checking (valid case, unknown field, missing field, mismatch,
not-a-struct, undefined name).

Closes #4. ## Summary - `TyKind::Struct`/`TyKind::Enum`, nominal (carry a `name: Symbol`), with enum variant payloads staying `Option<Ty>` to distinguish a no-payload variant from a resolution failure. - `check_expr` gains a `name_hint: Option<Symbol>` parameter, populated only by `check_let`, so `struct { ... }`/`enum { ... }` declarations can be named without needing their own syntax for it (per `let X = struct {...}`). A `None` hint reports `NamelessStruct`/`NamelessEnum`. - `check_struct_literal` checks `Expr::StructLiteral` against its declared struct: name-based (not positional) field matching over the union of literal/declared field names, catching unknown fields (`StructFieldNotDefined`), missing required fields (`MissingStructType`), and field type mismatches (`StructFieldMismatch`) in one pass. A literal against an undeclared or non-struct name reports `NoStruct`. - Enum variant construction/matching (`Reserved(slot)`, `match`) is explicitly out of scope — no `EnumLiteral` HIR node exists; that's `Expr::Call`/`Expr::Match` checking, later work. - `check_expr`'s match arms extracted into their own functions (`check_ident`/`check_block`/`check_fn`/`check_call`/`check_struct`/ `check_enum`/`check_struct_literal`) to keep it readable as more constructs are added. - `docs/type-checker-design.md` gets a new `## Issue #4` section documenting these decisions. ## Test plan - [x] `cargo test -p twill-check` — 123 tests passing, including 6 new tests each for struct/enum declaration checking and struct-literal checking (valid case, unknown field, missing field, mismatch, not-a-struct, undefined name).

jacksonopp added 3 commits

2026-09-03 01:40:31 +00:00

check struct and enum defs 8f37dae28d

check struct literal e9cd0d48ec

Document issue #4 design decisions in type-checker-design.md 0d290e2510

Covers the nominal Struct/Enum Ty shapes, the name_hint mechanism for
naming anonymous struct/enum declarations, the name-based (union-of-keys)
field matching in check_struct_literal, and the new diagnostics.

jacksonopp added 1 commit

2026-09-03 01:42:52 +00:00

update diagnostic messags 0af3056adf

jacksonopp added 1 commit

2026-09-03 01:44:47 +00:00

rename NoStruct to NotStruct 0325205cd9

jacksonopp merged commit 87fddeddc9 into main

2026-09-03 01:45:11 +00:00

jacksonopp deleted branch us4/type-check-struct-enum

2026-09-03 01:45:11 +00:00

jacksonopp referenced this pull request from a commit

2026-09-03 01:45:12 +00:00