M2compiler-V3/docs/summary_generics-2026-10-15.md

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:

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

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.