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Phase 6f: let = immutable, var = mutable (binding-only)

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Bindings now signal mutability the way Rust/Swift do, instead of `let` meaning
"local" and `var` meaning "module-level":

  - `let x = e`  -> immutable binding; a later `x = …` is a compile error
    (`cannot assign to immutable 'x' … use var`).
  - `var x = e`  -> mutable binding, at local OR module scope (position decides
    scope; the keyword decides mutability).
  - `const`      -> unchanged (compile-time).

Immutability is of the *binding*, not the object: `let n = new Node; n.kind = 1`
is fine (mutation through the reference); only rebinding `n` is rejected. The
check lives in emit_assign — a direct `name =` whose target is a `let` local
(loc_mut == 0) errors; field/index targets and `var`/param/loop bindings are
unaffected.

Delivered as three reseeds so the self-hosting compiler never had to compile
source its own rules would reject:
  A) add `var` as a local statement + per-local mutability tracking (loc_mut),
     no enforcement;
  B) migrate every reassigned `let` -> `var` across the compiler, runtime and
     examples (337 declarations), driven by a per-function, string/comment-aware
     scan (binding targets only, never `x.f =` / `x[i] =`);
  C) turn on the check. bootstrap-cfree (compiler vs its own source) and every
     golden build (which splices the runtime) then proved zero reassigned `let`
     was missed anywhere.

Also folded in: removed leftover debug instrumentation in block() (a `cur=` /
print_int(777…) trace on the separator-error path) and fixed parse.ludic's stale
header comment (no more `struct`). Reseeded (21711 lines); C-free fixpoint holds;
goldens identical; 17/17; vocab + doc-fences clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Orkun ÇAKILKAYA 2026-08-27 23:52:59 +03:00
parent 573813609c
commit e1d7797e29
38 changed files with 2909 additions and 2778 deletions
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4
selfhost/emit_new.ludic
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@ -13,14 +13,14 @@ fn emit_new_struct(name: ptr) -> Val {
let lty = layout_ty(name)
let sz = emit_sizeof(lty)
let obj = emit_bind(sconcat("call ptr @malloc(i64 ", sconcat(sz, ")")))
let f = 0
var f = 0
while f < len(s.kids) {
let fd = s.kids[f]
let addr = nreg()
emit(" "); emit(addr); emit(" = getelementptr inbounds "); emit(lty)
emit(", ptr "); emit(obj); emit(", i32 0, i32 "); emit(itoa(f)); emit("\n")
let lt = llty(fd.ty)
let v = "0"
var v = "0"
if streq(lt, "ptr") { v = "null" }
if not ptr_is_null(fd.a) { let dv = emit_expr(fd.a); v = dv.code }
emit(" store "); emit(lt); emit(" "); emit(v); emit(", ptr "); emit(addr); emit("\n")