# Generics status — 2026-10-15

Branch **`resolve-check`** (contains `v3-generics-inc2`, 19 commits back).
Design: `docs/analysis_generics.md`; inc2 record:
`docs/summary_generics-inc2.md`. Suite **196/196**, incl.
`GenericProg` (single-formal `Ident(INTEGER)`, exit 42).

## What works

ISO 10514-2 form: `GENERIC DEFINITION/IMPLEMENTATION MODULE M(T :
TYPE)` plus refinement `DEFINITION MODULE X = M(actual)`. A refinement
instantiates by **re-parsing the generic's source** with the formals
bound to the actuals (`SymTab.EnterTypeParamBound`, `Reenter`; driver
registry maps generic name → file; the abstract template is never
emitted). Re-verified live: `FROM IntId IMPORT Id; Id(42)` → exit 42.

## CORRECTED 2026-10-16 — multi-formal instantiation *works*

The "fresh finding" that a two-formal generic fails to link was **my
incomplete test**: I supplied only a *definition* refinement
(`X = M(...)`) and no *implementation* refinement
(`IMPLEMENTATION MODULE X = M(...)`), so the instance had no body to
emit (the single-formal tests always ship both `g_intid.def` and
`g_intid.mod`).  With both refinements, `Pair(T, U)` instantiates
correctly, using **both** type parameters:

```modula2
GENERIC DEFINITION MODULE Pair (T : TYPE; U : TYPE);
PROCEDURE First(x : T; y : U) : T;
PROCEDURE Second(x : T; y : U) : U;
END Pair.
DEFINITION/IMPLEMENTATION MODULE IntChar = Pair(INTEGER, CHAR);
```

`First(7, "A") + ORD(Second(1, "B"))` compiles, links and returns 73.
Locked as the suite test `PairProg` (`g_pair.*`, `g_intchar.*`,
`g_pair_prog.mod`).  Suite **202/202**.

Real (smaller) gap: if only the *definition* refinement is given, the
module compiles clean but the link fails with no compile-time
diagnostic.  Worth a driver-level "refinement has a definition but no
implementation" warning — not a correctness bug, a UX one.

## Still open (unchanged from inc2)

- Increment 3: const/procedure parameters, constraints.
- `GENERIC CLASS`; generics with a program module.
- Instance dedup (each refinement re-instantiates today).
- A refinement must supply both a definition and an implementation.
- Ordering rule stands: refinement file after the generic's file,
  generic def before its impl.

## Still open (unchanged from inc2)

- Fix multi-formal instantiation (bug in shipped scope — sensible first
  step before new features).
- Increment 3: const/procedure parameters, constraints.
- `GENERIC CLASS`; generics with a program module.
- Instance dedup (each refinement re-instantiates today).
- Ordering rule stands: refinement file after the generic's file,
  generic def before its impl.

## Resume

```sh
cd .../m2compiler-V3/compiler
./M2 tests/g_ident.def tests/g_ident.mod tests/g_intid.def \
  tests/g_intid.mod tests/g_prog.mod   # GenericProg session
```

Multi-formal repro: rebuild `/tmp/opencode/g2*.mod` per §"Fresh
finding" above, then `qbe` + `cc` to observe the link failure.