I think something like this would handle it

  const std = @import("std");
  
  fn snoob(x_: anytype) @TypeOf(x_) {
    const T = @TypeOf(x_);
    const U = comptime std.meta.Int(.unsigned, std.meta.bitCount(T));
    const x = @bitCast(U, x_);
    const tz = @ctz(x);
    const pc = @popCount(x);
    const L2U = comptime std.meta.Int(.unsigned, std.meta.bitCount(@TypeOf(tz))-1);
    if (tz + pc == std.meta.bitCount(T)) {
      if (pc == 0) {
        return 0;
      }
      return @bitCast(T, (@bitCast(U, x) >> @intCast(L2U, tz)));
    }
    const smallest = @as(U, 1) << @intCast(L2U, tz);
    const ripple = x + smallest;
    const ones = ((x ^ ripple) >> 2) >> @intCast(L2U, tz);
    return ripple | ones;
  }
  
  pub fn main() void { std.debug.print("Hello, {d}!", .{snoob(@as(u32,5))}); }

In addition to the stated problems with wraparound and zero (claimed fixed here) the implementation in this header file seems to have some potential correctness issue if you pass in a signed type and end up performing right shifts on values with the sign bit set and your compiler decides this means you want sign extension.