As I was working through 「SML＃で始める実践MLプログラミング」 I tried creating a record with field names such as

{ 01_foo = someVal .. }

Apparently field names cannot start with 0, but the error I got was:

% make && ./main
smlsharp -O2 -o main.o -c main.sml
main.sml:12.4(211)-12.5(212) Error: illeagal _ keyword

The correct spelling is illegal.

I dug deeper and found the string illeagal consistently used across the codebase. This PR addresses all the instances I was able to track down.