docs: generics increment 2 summary

docs/summary_generics-inc2.md

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+# Session summary — 2026-10-08 (b): generics increment 2
+
+Tag `v3-generics-inc2`, branch `generics-inc2` (off `generics-inc1`).
+Suite **190/190**; fixpoint **OK** (**3,472,663 bytes**).
+
+Increment 2 of ISO 10514-2 generics: a refinement now **instantiates**
+the generic by re-parsing its source with the type formals bound to the
+actuals — the design sketched in `docs/analysis_generics.md`.
+
+## 1. What the syntax does now
+
+```modula2
+GENERIC DEFINITION MODULE Ident (T : TYPE);      (* the template *)
+PROCEDURE Id(x : T) : T;
+END Ident.
+
+DEFINITION MODULE IntId = Ident(INTEGER);        (* a refinement *)
+END IntId.
+```
+
+`IntId` is now a real module: its `Id` takes/returns `INTEGER`.  A
+program `FROM IntId IMPORT Id; … Id(42)` compiles and returns 42.
+
+## 2. How it works
+
+Increment 1 left: grammar recognition of the four generic module
+categories, formals entered as unresolved aliases (`EnterTypeParam`),
+and refinements recorded (`refInst`/`refGen`/`refActual`).
+
+Increment 2 adds the instantiation pass:
+
+- **Grammar** (`M2.atg`): an instantiation context
+  `instActive`/`instName`/`instActual[]`/`instFk`, with accessors
+  (`InstBegin`/`InstAddActual`/`InstEnd`/`InInst`) and unit/refinement
+  queries (`UnitNameGet`/`UnitIsGeneric`/`UnitIsDefModule`,
+  `RefineSeen`/`RefineIsDef`/`RefineInst`/`RefineGen`/`RefineActual*`),
+  exported via `parser.frm`.  When `instActive`, `DefUnit`/`ImplUnit`
+  rename the module to `instName`, `GenericFormal` binds each formal to
+  the matching actual (`EnterTypeParamBound`), and the `END` name is
+  overridden.
+- **SymTab**: `EnterTypeParamBound` (a formal alias whose target is the
+  actual) and `Reenter` (re-enter an already-registered module scope —
+  the refinement registered `X` before the re-parse).
+- **Driver** (`compiler.frm`): records each generic def/impl *file*
+  (module name → path) when parsed and does **not** emit the abstract
+  template; on a refinement it re-opens the generic's file, sets the
+  instantiation context, re-parses, and lowers the resulting unit.
+
+## 3. Self-hosting constraints hit (and fixed)
+
+The self-hosted compiler is stricter than gm2; three fixes were needed:
+
+- helper procedures must be declared **before** their callers
+  (`CopyNm`) — moved the accessor block below it;
+- an **array element** may not be passed to a `VAR ARRAY OF CHAR`
+  formal, and an **open array** may not be assigned to a fixed array —
+  the registry copies element-by-element and looks up by index;
+- gm2 rejects an **anonymous fixed-size array** as a formal parameter
+  type — named types `GName`/`GPath` were introduced.
+
+## 4. Test
+
+`g_ident.def/.mod` (the generic `Ident(T)`), `g_intid.def/.mod`
+(`IntId = Ident(INTEGER)`) and `g_prog.mod` (`Id(42)`).
+`run_tests.sh`: `expect_run_files GenericProg 42 …` → PASS.
+
+## 5. Scope / remaining
+
+- Multiple formals and multiple actuals are threaded but only a single
+  `T` is exercised; `const`/procedure parameters and constraints are
+  increment 3.
+- Instance **dedup** is not implemented (each refinement re-instantiates).
+- `GENERIC CLASS`, and generics with a program module, are untouched.
+- The refinement file must appear **after** the generic's file in the
+  session (the registry is populated as files are parsed), and the
+  generic's def must precede its impl.
+
+## Resume
+
+```sh
+cd .../m2compiler-V3
+./bootstrap/fixpoint.sh                       # FIXPOINT OK
+cd compiler && ./build.sh && ./run_tests.sh   # 190/190
+```
+
+## Files
+
+`compiler/src/M2.atg`, `compiler/src/parser.frm`,
+`compiler/src/SymTab.def`/`.mod`, `compiler/src/compiler.frm`,
+`compiler/tests/g_ident.*`, `g_intid.*`, `g_prog.mod`,
+`compiler/run_tests.sh`, this doc.