fix: support Date as a typed-array element and island-crossing type

packages/compiler/src/backend/emission/emit-exprs.ts

@@ -203,7 +203,7 @@ function streamTypedRefAdapter(
       `  ScrDyn *d = scr_dyn_new_arr();`,
       `  for (size_t sc_i = 0; sc_i < v->len; sc_i++) {`,
     );
-    if (elem.kind === "f64") {
+    if (elem.kind === "f64" || elem.kind === "date") {
       lines.push(
         `    scr_dyn_arr_push(d, ${box(elem, "scr_arr_get_f64(v, (double)sc_i)")});`,
       );
@@ -384,7 +384,7 @@ function streamFromArrayAdapter(
     );
   }
   d.push(`${sig} { /* ReadableStream.from array<${key}> */`);
-  if (elem.kind === "f64") {
+  if (elem.kind === "f64" || elem.kind === "date") {
     d.push(
       `  return ${E.toDynHelper(elem)}(scr_arr_get_f64(sc_a, sc_i));`,
     );
@@ -3004,7 +3004,7 @@ export function emitExpr(E: CEmitter, e: IrExpr): Temp {
           if (e.type.inner.kind !== "array") throw new InternalCompilerError("emitter bug: promise.all result");
           const elem = e.type.inner.elem;
           const store =
-            elem.kind === "f64"
+            (elem.kind === "f64" || elem.kind === "date")
               ? "scr_promise_all_store_f64"
               : elem.kind === "bool"
                 ? "scr_promise_all_store_bool"
@@ -7438,6 +7438,8 @@ export function emitExpr(E: CEmitter, e: IrExpr): Temp {
         const v = E.emitExpr(e.value);
         switch (e.value.type.kind) {
           case "f64":
+          case "date":
+            // Date crossing IN: passed as millisecond timestamp (a JS number).
             return E.newTemp(e.type, `scr_jsval_from_f64(${v.name})`);
           case "bool":
             return E.newTemp(e.type, `scr_jsval_from_bool(${v.name})`);

packages/compiler/src/backend/emission/emit-types.ts

@@ -264,6 +264,8 @@ export function elemKindC(elem: IrType): string {
   }
   switch (elem.kind) {
     case "f64":
+    // Dates are epoch-ms f64 scalars at the C level — use the same slot.
+    case "date":
       return "SCR_ELEM_F64";
     case "bool":
       return "SCR_ELEM_BOOL";
@@ -303,7 +305,6 @@ export function elemKindC(elem: IrType): string {
     // pointer identity — exactly JS function identity.
     case "func":
       return "SCR_ELEM_REF";
-    case "date":
     case "procStream":
     case "undefinedT":
     case "nullT":
@@ -381,7 +382,8 @@ export const DV_SET_KIND_C: Record<string, string> = {
 /** Runtime accessor suffix for an element type: arrays store f64 and bool
  * unboxed and everything refcounted as a pointer (`_ref`). */
 export function elemAccess(elem: IrType): "f64" | "bool" | "ref" {
-  return elem.kind === "f64" ? "f64" : elem.kind === "bool" ? "bool" : "ref";
+  // Dates are stored as epoch-ms f64 scalars at the C level.
+  return (elem.kind === "f64" || elem.kind === "date") ? "f64" : elem.kind === "bool" ? "bool" : "ref";
 }
 
 /** Runtime suffix for a map's KEY kind (f64 with SameValueZero, or string

packages/compiler/src/backend/llvm/emitter.ts

@@ -7812,6 +7812,8 @@ class LlEmitter {
     };
     switch (e.value.type.kind) {
       case "f64":
+      case "date":
+        // Date crossing IN: passed as millisecond timestamp (a JS number).
         return simple("scr_jsval_from_f64", "double", false);
       case "bool":
         return simple("scr_jsval_from_bool", "i1", false);

packages/compiler/src/backend/llvm/shapes.ts

@@ -265,13 +265,15 @@ export function traceArg(host: ShapeHost, t: IrType): string {
 /** Runtime accessor suffix for an element type (matches emit-types.ts:
  * f64 and bool unboxed, everything refcounted through the `_ref` family). */
 export function elemAccess(elem: IrType): "f64" | "bool" | "ref" {
-  return elem.kind === "f64" ? "f64" : elem.kind === "bool" ? "bool" : "ref";
+  return (elem.kind === "f64" || elem.kind === "date") ? "f64" : elem.kind === "bool" ? "bool" : "ref";
 }
 
 /** The ScrElemKind constant for the plain (non-REF) construction path. */
 function elemKindNum(elem: IrType): number {
   switch (elem.kind) {
     case "f64":
+    // Dates are epoch-ms f64 scalars at the C level — same slot kind.
+    case "date":
       return 0; // SCR_ELEM_F64
     case "bool":
       return 1; // SCR_ELEM_BOOL

packages/compiler/src/frontend/lowering/lowerer.ts

@@ -6109,9 +6109,10 @@ export class Lowerer {
   jsvalLiftable(t: IrType, visiting: Set<string> = new Set()): boolean {
     if (t.kind === "jsval") return true;
     if (this.boundarySafe(t)) return true;
-    // Typed arrays and URLs marshal IN without joining the round-trip
-    // (JSON) set: an engine typed-array copy / an engine URL from href.
-    if (t.kind === "bytes" || t.kind === "url") return true;
+    // Typed arrays, URLs, and Dates marshal IN without joining the round-trip
+    // (JSON) set: an engine typed-array copy / an engine URL from href /
+    // a Date as its millisecond timestamp (scr_jsval_from_f64).
+    if (t.kind === "bytes" || t.kind === "url" || t.kind === "date") return true;
     // Checked-dynamic values deep-copy in (scr_jsval_from_dyn — data
     // kinds; a boxed function/handle/promise throws at runtime).
     if (t.kind === "dyn") return true;
@@ -6162,7 +6163,7 @@ export class Lowerer {
     if (this.boundarySafe(e.type)) {
       return { kind: "jsMarshal", value: e, type: JSVAL, loc };
     }
-    if (e.type.kind === "bytes" || e.type.kind === "url") {
+    if (e.type.kind === "bytes" || e.type.kind === "url" || e.type.kind === "date") {
       return { kind: "jsMarshal", value: e, type: JSVAL, loc };
     }
     if (e.type.kind === "record") {

packages/compiler/src/ir/nodes.ts

@@ -518,6 +518,9 @@ export function isSupportedArrayElem(t: IrType): boolean {
     case "netServer":
     case "symbol":
     case "classval":
+    // Dates are scalar f64 (epoch-ms) at the C level — stored in SCR_ELEM_F64
+    // slots. Array element reads re-box the ms value into a date handle.
+    case "date":
       return true;
     default:
       return false;