M2compiler-V3/docs/summary_step8.2.md

V3 step 8.2 — self-compile gaps fixed for SymTab (104/104)

Closing the measured step-8.1 gaps so V3 can compile its own sources. Suite 104/104 (new t_constfold), build warning-free.

What landed

1. Named-CONST constant folding. SymTab now stores a CONST's literal value text (SetSymVal/GetSymVal, new val field); the grammar folds a CONST reference to its literal and folds integer + - * DIV MOD on two literals (QbeGen.Fold2). So ARRAY [0 .. MaxPend - 1] and friends fold, in bounds, subranges, sets, FOR limits and expressions. New test tests/t_constfold.mod (42).

2. Forward type references in a TYPE block. POINTER TO X where X is declared later now resolves: SymTab.ForwardType enters an unresolved alias inside a type block, completed by the later TypeItem via the existing opaque SetTarget path (BeginTypeBlock/EndTypeBlock gate it). TypeIdent uses it on lookup failure instead of erroring 201.

3. Trailing ; before a record's END. RecordType accepts RECORD fieldlist [;] END (grammar now { ";" [ RecField ] }).

4. Qualified type names (FileIO.File). TypeIdent accepts Module.Type via SymTab.QualType; a bare module name as a type still reports 221.

5. Capacity. MaxTypes 256→4096, MaxPend 64→256, MaxMods 32→64. The compiler's own sources exceed 256 type descriptors (this alone caused ~465 spurious 230s).

6. Compact zero-filled array data. ArrData emits QBE { l n, z n*esz } instead of one w 0 per element. Emitting a million-element sessBuf/nestBufs element-by-element was the apparent "hang" once the type table stopped truncating them.

7. Source hygiene. Resolve moved ahead of PushClassScope in SymTab.mod (declaration-before-use; ISO-clean).

Result

SymTab.def + SymTab.mod now compile clean under V3 (0 errors; verified with a stub program module). QbeGen is close: down from 205/465 errors to 85 invalid call + 38 undeclared + 1 invalid Statement, dominated by two remaining gaps:

• Within-module forward procedure calls (10 distinct callees: Revive, LocAdd, ResClass, HApp, LocFindUp, UpAddrOf, AllocLocal, FlushStrings, HeapSize, ArrData). gm2 hoists these; ISO wants declaration-before-use or FORWARD.
• Single-character string literals ("0", "$", "-") are typed CHAR, so passing them to ARRAY OF CHAR formals (Cpy(d, "0")) reports "invalid call". V3 needs context-sensitive CHAR/string coercion.

Files

compiler/src/{M2.atg,SymTab.def,SymTab.mod,QbeGen.def,QbeGen.mod}, compiler/tests/t_constfold.mod, compiler/run_tests.sh.