Bad field gives ArrayIndexOutOfBoundsException

[julianhyde]

Bad field gives ArrayIndexOutOfBoundsException. For example,

let val e1 = {name="Fred",empno=10} in #ename e1 end;
java.lang.ArrayIndexOutOfBoundsException: Index -1 out of bounds for length 2
	at java.base/java.util.Arrays$ArrayList.get(Arrays.java:4351)
	at net.hydromatic.morel.eval.Codes.lambda$nth$23(Codes.java:335)
	at net.hydromatic.morel.eval.Codes.lambda$apply$20(Codes.java:206)
	at net.hydromatic.morel.eval.Codes.lambda$let$17(Codes.java:177)
	at net.hydromatic.morel.compile.Compiler.lambda$compileValBind$8(Compiler.java:512)
	at net.hydromatic.morel.compile.Compiler$1.eval(Compiler.java:76)
	at net.hydromatic.morel.Shell.run(Shell.java:250)
	at net.hydromatic.morel.Shell.main(Shell.java:75)

It should give a better error message.

Here's what sml does in a similar situation:

- let val e1 = {name="Fred",empno=10} in #name e1 end;
val it = "Fred" : string
- let val e1 = {name="Fred",empno=10} in #ename e1 end;
stdIn:2.40-2.49 Error: operator and operand don't agree [record labels]
  operator domain: {ename:'Y; 'Z}
  operand:         {empno:[int ty], name:string}
  in expression:
    (fn {ename=ename,...} => ename) e1

The problem also occurs in from expressions:

from e in [{empno=10, name="Fred"}] yield {no = #empno e, name = #ename e};
java.lang.ArrayIndexOutOfBoundsException: Index -1 out of bounds for length 2
	at java.base/java.util.Arrays$ArrayList.get(Arrays.java:4351)
	at net.hydromatic.morel.eval.Codes.lambda$nth$23(Codes.java:335)
	at net.hydromatic.morel.eval.Codes.lambda$apply$20(Codes.java:206)
	at net.hydromatic.morel.eval.Codes$TupleCode.eval(Codes.java:891)
	at net.hydromatic.morel.eval.Codes$2.loop(Codes.java:246)
	at net.hydromatic.morel.eval.Codes$2.loop(Codes.java:253)
	at net.hydromatic.morel.eval.Codes$2.eval(Codes.java:236)
	at net.hydromatic.morel.compile.Compiler.lambda$compileValBind$8(Compiler.java:512)
	at net.hydromatic.morel.compile.Compiler$1.eval(Compiler.java:76)
	at net.hydromatic.morel.Shell.run(Shell.java:250)
	at net.hydromatic.morel.Shell.main(Shell.java:75)