# Step: CLASS finished (sibling calls + init body)

Tag `v3-class-finish`. Suite **146/146**; fixpoint **OK**
(image **2,313,762 bytes**).

Removes the last two implementable `230`s in the Clarion class area
(the third, multiple parents, stays a deliberate limitation).

## Sibling-method calls

Inside a `CLASS IMPLEMENTATION` body, a **bare method name** is a call
on `THIS`:

```modula-2
CLASS IMPLEMENTATION Acc;
  PROCEDURE Add(v : INTEGER);       BEGIN total := total + v END Add;
  PROCEDURE AddTwice(a, b : INTEGER);
  BEGIN Add(a); Add(b) END AddTwice;      (* sibling calls *)
END Acc;
```

- `SymTab` tracks the innermost open implementation (`PushImplClass`/
  `PopImplClass`/`CurImplClass`); `ClassImplRest` pushes it.
- `Design`: when an identifier is not found in the ordinary scopes but
  the current implementation class has a method of that name, it binds
  the method, arms `THIS` as the receiver (`QbeGen.ThisBase` +
  `ArmRecv`), and marks a static (or virtual, if `VIRTUAL`) call.

## Class `BEGIN … END` init body

A class's initialisation body now compiles and runs **once at
startup**, as `<Class>_init` (registered in the same list as module
init functions, called from `main`):

```modula-2
CLASS IMPLEMENTATION C;
  ...
BEGIN
  g := 41                 (* runs at startup *)
END C;
```

A body that references instance fields has no receiver and still
reports 230 (class statics do not exist in V3).

## Multiple parents — deliberate

`CLASS Multi (A, B)` (more than one parent) remains 230: the design is
single inheritance only (`docs/OOP.txt`). `showcase5.mod` keeps that
rejection under test.

## Tests

- `t_classsibling.mod` (7): sibling calls.
- `t_classinit.mod` (42): the init body sets a global before `main`.
- `t_class.mod` promoted from a reject test to a run test (0).
- `showcase5.mod` still rejects (multiple parents).

## Files

`compiler/src/SymTab.def`/`.mod` (`implStk`, `PushImplClass`/
`PopImplClass`/`CurImplClass`), `compiler/src/M2.atg` (`ClassImplRest`
push/pop + init body, `Design` sibling-call branch),
`compiler/tests/{t_classsibling,t_classinit}.mod`,
`compiler/run_tests.sh`, `docs/{features,OOP}.txt`.