fix: validate u32 range before casting RtlNtStatusToDosError result to u16

Replace @truncate with an explicit range check (raw > maxInt(u16)) before
@intCast to avoid silently wrapping out-of-range values from the u32
return of RtlNtStatusToDosError.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/errno/windows_errno.zig

@@ -968,7 +968,7 @@ pub const SystemErrno = enum(u16) {
         if (@TypeOf(code) == u16 or (@TypeOf(code) == c_int and code > 0)) {
             // Win32Error and WSA Error codes
             if (code <= @intFromEnum(Win32Error.IO_REISSUE_AS_CACHED) or (code >= @intFromEnum(Win32Error.WSAEINTR) and code <= @intFromEnum(Win32Error.WSA_QOS_RESERVED_PETYPE))) {
-                return init(@as(Win32Error, @enumFromInt(code)));
+                return init(std.meta.intToEnum(Win32Error, code) catch return null);
             } else {
                 // uv error codes
                 inline for (@typeInfo(SystemErrno).@"enum".fields) |field| {
@@ -988,7 +988,7 @@ pub const SystemErrno = enum(u16) {
         }
 
         if (comptime @TypeOf(code) == Win32Error or @TypeOf(code) == std.os.windows.Win32Error) {
-            return switch (@as(Win32Error, @enumFromInt(@intFromEnum(code)))) {
+            return switch (std.meta.intToEnum(Win32Error, @intFromEnum(code)) catch return null) {
                 Win32Error.NOACCESS => SystemErrno.EACCES,
                 Win32Error.WSAEACCES => SystemErrno.EACCES,
                 Win32Error.ELEVATION_REQUIRED => SystemErrno.EACCES,

src/windows.zig

@@ -149,7 +149,7 @@ pub extern "kernel32" fn SetCurrentDirectoryW(
     lpPathName: win32.LPCWSTR,
 ) callconv(.winapi) win32.BOOL;
 pub const SetCurrentDirectory = SetCurrentDirectoryW;
-pub extern "ntdll" fn RtlNtStatusToDosError(win32.NTSTATUS) callconv(.winapi) Win32Error;
+pub extern "ntdll" fn RtlNtStatusToDosError(win32.NTSTATUS) callconv(.winapi) u32;
 pub extern "advapi32" fn SaferiIsExecutableFileType(szFullPathname: win32.LPCWSTR, bFromShellExecute: win32.BOOLEAN) callconv(.winapi) win32.BOOL;
 // This was originally copied from Zig's standard library
 /// Codes are from https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-erref/18d8fbe8-a967-4f1c-ae50-99ca8e491d2d
@@ -2952,7 +2952,8 @@ pub const Win32Error = enum(u16) {
     pub const WSA_QOS_RESERVED_PETYPE: Win32Error = @enumFromInt(11031);
 
     pub fn get() Win32Error {
-        return @enumFromInt(@intFromEnum(bun.windows.kernel32.GetLastError()));
+        const raw: u16 = @intFromEnum(bun.windows.kernel32.GetLastError());
+        return std.meta.intToEnum(Win32Error, raw) catch .MR_MID_NOT_FOUND;
     }
 
     pub fn int(this: Win32Error) u16 {
@@ -2971,7 +2972,12 @@ pub const Win32Error = enum(u16) {
     }
 
     pub fn fromNTStatus(status: win32.NTSTATUS) Win32Error {
-        return RtlNtStatusToDosError(status);
+        // RtlNtStatusToDosError returns a u32 Win32 error code that may not be
+        // in our Win32Error enum subset. Safely convert to avoid panic on
+        // invalid enum values.
+        const raw = RtlNtStatusToDosError(status);
+        if (raw > std.math.maxInt(u16)) return .MR_MID_NOT_FOUND;
+        return std.meta.intToEnum(Win32Error, @as(u16, @intCast(raw))) catch .MR_MID_NOT_FOUND;
     }
 };