print missing key in error message

[mahrud]

I often run into mysterious error messages like this:

stdio:11:59:(3): error: key not found in hash table

In this instance, I was trying to figure out the issue mentioned in this comment, and this error is utterly unhelpful.

@DanGrayson I figure the best solution is to perhaps print the key in the error message, which happens here:

M2/M2/Macaulay2/d/hashtables.dd

Lines 319 to 326 in 7ba2678

	export lookup1force(object:HashTable,key:Expr,keyhash:int):Expr := (
	keymod := int(keyhash & (length(object.table)-1));
	bucket := object.table.keymod;
	while bucket != bucket.next do (
	if bucket.key == key || bucket.hash == keyhash && equal(bucket.key,key)==True then return bucket.value;
	bucket = bucket.next;
	);
	buildErrorPacket("key not found in hash table"));

One wrinkle is that the key can be any Expr object, and probably turning it into a string is not always the best idea. Could we print it if it's an integer or string perhaps? Do you have any better ideas?

[DanGrayson]

In robust.m2 are silentRobustNetWithClass and silentRobustNet, which print things while limiting the size. They are used in error messages like this one:

i4 : (300:1) + (300:2)
stdio:4:9:(3): error: no method for binary operator + applied to objects:
--            (1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1. (of class Sequence)
--      +     (2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2. (of class Sequence)

(I wish there were 3 dots instead of just one at the cutoff points.)