for...of on Map obtained via local alias of class field yields incorrect keys / zero iterations #305

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1. codehz

   added

   bugConfirmed defect or regressionConfirmed defect or regression

   on Apr 30, 2026
2. proggeramlug

   added a commit that references this issue on Apr 30, 2026

   fix: closes #304 + #305 — array.length=N truncate + class-field local…

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   fb18ca7
3. proggeramlug commented on Apr 30, 2026

   

   proggeramlug

   on Apr 30, 2026

   Contributor

   More actions

   Fixed in v0.5.397. const m = this.map; for-of m now iterates correctly because the this.<field> shape is now resolved through the class_field_types registry (originally landed in v0.5.388 for #302).

   The same fix transparently covers const s = this.items (Set field) and const a = this.xs (number[] field) — any local alias of a typed class field now inherits the correct generic / array element type so for-of and method dispatch take the right fast path.

   Regression test: test-files/test_issue_305_local_alias_class_field_map.ts (4 cases — Map local alias, Map this.x direct comparison, Set local alias, Array local alias).
4. proggeramlug

   closed this as completedon Apr 30, 2026
5. proggeramlug

   added a commit that references this issue on Apr 30, 2026

   fix(hir): closes #310 — traverse `export * as X from ...` namespace r…

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   57e6887
6. codehz commented on Apr 30, 2026

   

   codehz

   on Apr 30, 2026

   Author

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   new repro in 0.5.415

   // Minimal reproduction for perry bug:
   // `for-of` on a Map stored in a class field does not iterate.
   //
   // Root cause: perry does not expose Map.prototype[Symbol.iterator] when the Map
   // is accessed through `this` (class field access). As a result, the generated
   // native code cannot find the iterator and silently skips the loop body.
   //
   // Workaround: use `.entries()` / `.keys()` / `.values()` explicitly.
   //
   // Impact on @codehz/ecs: CommandBuffer.execute() contains
   //
   //   for (const [entityId, commands] of entityCommands) { ... }
   //
   // where `entityCommands` is a class-field Map. Because the loop body never
   // runs, every command is silently dropped and world.sync() becomes a no-op,
   // making world.has() / world.get() return wrong results after world.set().
   
   // ── Repro 1: for-of directly on a class-field Map ────────────────────────
   class MapHolder {
     private map = new Map<number, string>();
   
     add(k: number, v: string) {
       this.map.set(k, v);
     }
   
     iterate() {
       console.log(`map.size = ${this.map.size}`);
       // Bug: loop body never executes even though size = 2
       console.log("for-of this.map (default iterator):");
       for (const [k, v] of this.map) {
         console.log(`  k=${k}, v=${v}`);
       }
       // Workaround: explicit .entries() works fine
       console.log("for-of this.map.entries() (workaround):");
       for (const [k, v] of this.map.entries()) {
         console.log(`  k=${k}, v=${v}`);
       }
     }
   }
   
   const holder = new MapHolder();
   holder.add(1, "hello");
   holder.add(2, "world");
   holder.iterate();
   
   // ── Repro 2: local variable assigned from class-field Map ─────────────────
   // Assigning to a local variable does NOT restore proper iteration –
   // perry appears to track the "this-access" origin of the value.
   class LocalAlias {
     private map = new Map<number, string>();
   
     add(k: number, v: string) {
       this.map.set(k, v);
     }
   
     iterate() {
       const local = this.map;
       console.log(`local.size = ${local.size}`);
       console.log("for-of local (assigned from this.map):");
       for (const [k, v] of local) {
         console.log(`  k=${k}, v=${v}`); // NEVER prints in perry
       }
     }
   }
   
   const la = new LocalAlias();
   la.add(10, "foo");
   la.add(20, "bar");
   la.iterate();
   
   // ── Control: module-scope Map (works correctly) ───────────────────────────
   const moduleMap = new Map<number, string>();
   moduleMap.set(100, "a");
   moduleMap.set(200, "b");
   console.log("for-of moduleMap (module-scope, control):");
   for (const [k, v] of moduleMap) {
     console.log(`  k=${k}, v=${v}`); // prints correctly
   }
   
   // ── Control: local variable inside a plain function (works correctly) ──────
   function localMapTest() {
     const m = new Map<number, string>();
     m.set(1000, "x");
     m.set(2000, "y");
     console.log("for-of local map inside function (control):");
     for (const [k, v] of m) {
       console.log(`  k=${k}, v=${v}`); // prints correctly
     }
   }
   localMapTest();
   
   // ── Symptom: Symbol.iterator is undefined on class-field Map ──────────────
   class IterCheck {
     private map = new Map<number, string>();
     run() {
       const m = this.map as any;
       console.log(`typeof this.map[Symbol.iterator] = ${typeof m[Symbol.iterator]}`);
       // Expected: "function"
       // Perry:    "undefined"
     }
   }
   new IterCheck().run();
   
   // ─────────────────────────────────────────────────────────────────────────────
   // Expected output (bun / node):
   //
   //   map.size = 2
   //   for-of this.map (default iterator):
   //     k=1, v=hello
   //     k=2, v=world
   //   for-of this.map.entries() (workaround):
   //     k=1, v=hello
   //     k=2, v=world
   //   local.size = 2
   //   for-of local (assigned from this.map):
   //     k=10, v=foo
   //     k=20, v=bar
   //   for-of moduleMap (module-scope, control):
   //     k=100, v=a
   //     k=200, v=b
   //   for-of local map inside function (control):
   //     k=1000, v=x
   //     k=2000, v=y
   //   typeof this.map[Symbol.iterator] = function
   //
   // Actual output in perry (compiled native):
   //
   //   map.size = 2
   //   for-of this.map (default iterator):          <- body skipped entirely
   //   for-of this.map.entries() (workaround):
   //     k=1, v=hello
   //     k=2, v=world
   //   local.size = 2
   //   for-of local (assigned from this.map):       <- body skipped entirely
   //   for-of moduleMap (module-scope, control):
   //     k=100, v=a
   //     k=200, v=b
   //   for-of local map inside function (control):
   //     k=1000, v=x
   //     k=2000, v=y
   //   typeof this.map[Symbol.iterator] = undefined <- should be "function"
7. proggeramlug

   reopened this on Apr 30, 2026
8. proggeramlug

   closed this as completedin f1d461con Apr 30, 2026