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Update Phase 3 interface status and design notes in design doc

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Mark is/as interface operators, IInterface built-in, and 2-field typeinfo
(with impllist) as Done.  Expand TYPEID entry to cover the impllist
data layout.
This commit is contained in:
Graeme Geldenhuys 2026-04-21 21:51:24 +01:00
parent 514c0fb122
commit ffcb1a041f
1 changed files with 15 additions and 12 deletions
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27
docs/design.adoc
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@ -724,10 +724,12 @@ are required for correct generic type bounds).
(zero-GUID design); `TInterfaceTypeDef` AST node; `tkIntf` token reused from (zero-GUID design); `TInterfaceTypeDef` AST node; `tkIntf` token reused from
unit interface section (context disambiguates) unit interface section (context disambiguates)
| TYPEID generation | TYPEID generation + impllist
| Done | Done
| `data $typeinfo_IFoo = { l 0 }` — address of block IS the identity token; | `data $typeinfo_IFoo = { l 0 }` — address IS identity token; class typeinfo
emitted by `EmitInterfaceDefs`; used for future `is`/`as` interface checks extended to 2 fields `{ l parent, l impllist }` where impllist is a
NULL-terminated `{typeinfo*, itab*}` pair array; emitted by `EmitInterfaceDefs`
/ `EmitTypeInfoDefs`
| Interface type in symbol table | Interface type in symbol table
| Done | Done
@ -761,19 +763,20 @@ are required for correct generic type bounds).
slot (slot × 8); indirect `call %fptr(l obj)` — same pattern as virtual dispatch slot (slot × 8); indirect `call %fptr(l obj)` — same pattern as virtual dispatch
| `as` cast to interface | `as` cast to interface
| Pending | Done
| Checked downcast: verify class implements interface via typeinfo pointer walk; | `F := T as IFoo` — codegen calls `_GetItab(obj, $typeinfo_IFoo)`; non-nil
raise `EInvalidCast` on failure result stored to `F_itab`; nil triggers `_Raise_InvalidCast`; handled
inline in `EmitAssignment` (fat-pointer LHS + TAsExpr RHS)
| `is` test against interface | `is` test against interface
| Pending | Done
| Runtime check: walk class `implements` list for matching typeinfo pointer; | `T is IFoo` — codegen calls `_ImplementsInterface(obj, $typeinfo_IFoo)`;
return boolean walks class typeinfo impllist chain; RTL in `blaise_exc.c`
| RTL: `IInterface` base | RTL: `IInterface` base
| Pending | Done
| Minimal `IInterface` declaration in `System.pas` stub: | `IInterface` pre-registered as built-in interface type in
`QueryInterface`, `_AddRef`, `_Release`; Blaise ARC replaces COM ref-counting `TSymbolTable.RegisterBuiltins`; no methods (ARC replaces COM ref-counting)
|=== |===