fix(runtime): Date.now/parse/UTC usable as first-class function values

crates/perry-hir/src/lower/expr_member.rs

@@ -1851,11 +1851,27 @@ fn lower_member_inner(ctx: &mut LoweringContext, member: &ast::MemberExpr) -> Re
                     // with detached `Math.log`.
                     let receiver_is_detached_console_read =
                         property == "console" && !member_is_call_callee;
+                    // #4596: `Date.now` / `Date.parse` / `Date.UTC` read as a
+                    // VALUE needs the reified Date constructor receiver so it
+                    // resolves to the real native function object (typeof
+                    // "function", correct `.name`/`.length`, callable). Undoing
+                    // the reroute collapses it to `GlobalGet(0).now`, for which
+                    // codegen has no intrinsic handler (unlike `Object.keys` /
+                    // `Math.max`) — so the read mis-folds to a number. Direct
+                    // CALLS (`Date.now()`) are intercepted earlier as
+                    // `Expr::DateNow` / `DateParse` / `DateUtc`, so gate on a
+                    // non-callee read.
+                    let outer_is_reified_date_static_value = !member_is_call_callee
+                        && property == "Date"
+                        && outer_static_member
+                            .map(|member| matches!(member, "now" | "parse" | "UTC"))
+                            .unwrap_or(false);
                     if !outer_is_prototype_or_proto
                         && !receiver_is_namespace_value
                         && !outer_is_websocket_static
                         && !outer_is_reified_object_static_value
                         && !outer_is_reified_builtin_static_value
+                        && !outer_is_reified_date_static_value
                         && !receiver_is_detached_console_read
                     {
                         object_expr = Expr::GlobalGet(0);

crates/perry-runtime/src/object/date_proto_thunks.rs

@@ -220,11 +220,17 @@ pub(crate) fn install_date_constructor_statics(ctor: *mut crate::closure::Closur
         1,
         false,
     );
-    super::global_this::install_constructor_static(
+    // `date_utc_static` collects *all* arguments into its `rest` param, so the
+    // call-arity (fixed params before the rest) must be 0 — otherwise the rest
+    // registration reserves 7 fixed slots and `Date.UTC(2020, 0)` (fewer than 7
+    // args) puts nothing in the rest array → js_date_utc([]) → NaN. The spec
+    // `.length` stays 7. (#4596)
+    super::global_this::install_constructor_static_with_call_arity(
         ctor,
         "UTC",
         date_utc_static as *const u8,
         7,
+        0,
         true,
     );
 }

crates/perry-runtime/src/object/global_this.rs

@@ -3430,7 +3430,7 @@ pub(super) fn install_constructor_static(
     install_constructor_static_with_call_arity(ctor, name, func_ptr, arity, arity, has_rest);
 }
 
-fn install_constructor_static_with_call_arity(
+pub(super) fn install_constructor_static_with_call_arity(
     ctor: *mut crate::closure::ClosureHeader,
     name: &str,
     func_ptr: *const u8,