From 2c6e5006ed3adb02f3bc7b364b2bbc688271d9f7 Mon Sep 17 00:00:00 2001
From: David <enfipy@gmail.com>
Date: Tue, 7 Apr 2026 00:47:21 +0500
Subject: [PATCH] Sema: fix comptime @ptrCast to optional slices

---
 src/Sema.zig           | 13 ++++++++++---
 test/behavior/cast.zig | 14 ++++++++++++++
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/src/Sema.zig b/src/Sema.zig
index 29d65047c68812b825d8c37952a700884714e0aa..0fafcc99b1c520b97d2677ba259f15240c7abf0b 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -21689,10 +21689,17 @@ fn ptrCastFull(
                 .equal_runtime_src_slice => unreachable,
                 .change_runtime_src_slice => unreachable,
             };
-            return Air.internedToRef(try pt.intern(.{ .slice = .{
-                .ty = dest_ty.toIntern(),
-                .ptr = (try pt.getCoerced(ptr_val, dest_ty.slicePtrFieldType(zcu))).toIntern(),
+            const dest_is_optional = dest_ty.zigTypeTag(zcu) == .optional;
+            const slice_ty = if (dest_is_optional) dest_ty.optionalChild(zcu) else dest_ty;
+            const slice_val = try pt.intern(.{ .slice = .{
+                .ty = slice_ty.toIntern(),
+                .ptr = (try pt.getCoerced(ptr_val, slice_ty.slicePtrFieldType(zcu))).toIntern(),
                 .len = len.toIntern(),
+            } });
+            if (!dest_is_optional) return Air.internedToRef(slice_val);
+            return Air.internedToRef(try pt.intern(.{ .opt = .{
+                .ty = dest_ty.toIntern(),
+                .val = slice_val,
             } }));
         } else {
             // Any to non-slice
diff --git a/test/behavior/cast.zig b/test/behavior/cast.zig
index d3f6ea5f48e09231888dbf285642cdb545b741fb..bb99b36863867f283da9478db9ee027aa2d8a5df 100644
--- a/test/behavior/cast.zig
+++ b/test/behavior/cast.zig
@@ -1544,6 +1544,20 @@ test "*const [N]null u8 to ?[]const u8" {
     try comptime S.doTheTest();
 }
 
+test "comptime @ptrCast to optional slice" {
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
+
+    const result: ?[]const u8 = comptime blk: {
+        const slice: []const u8 = "123";
+        break :blk @ptrCast(slice);
+    };
+
+    comptime assert(mem.eql(u8, result.?, "123"));
+    try expectEqualSlices(u8, "123", result.?);
+}
+
 test "cast between [*c]T and ?[*:0]T on fn parameter" {
     const S = struct {
         const Handler = ?fn ([*c]const u8) callconv(.c) void;
-- 
2.54.0