we should not crash here

src/fd.zig

@@ -303,11 +303,6 @@ pub const FDImpl = packed struct {
     }
 
     pub fn format(this: FDImpl, comptime fmt: []const u8, _: std.fmt.FormatOptions, writer: anytype) !void {
-        if (fmt.len == 1 and fmt[0] == 'd') {
-            try writer.print("{d}", .{this.system()});
-            return;
-        }
-
         if (fmt.len != 0) {
             @compileError("invalid format string for FDImpl.format. must be either '' or 'd'");
         }
@@ -316,6 +311,12 @@ pub const FDImpl = packed struct {
             try writer.writeAll("[invalid_fd]");
             return;
         }
+
+        if (fmt.len == 1 and fmt[0] == 'd') {
+            try writer.print("{d}", .{this.system()});
+            return;
+        }
+        
         switch (env.os) {
             else => {
                 const fd = this.system();