Setters' semantics are illogical: they don't get the value

[progval]

When using a setter (eg. {[] 'foo': {#getter undefined, #setter (func (a, b) { b })}}['foo' = 'bar']), b is not 'bar' as expected, but is an object.

The setter has no way to know what the “assigned” value is.
Indeed, looking at this code: https://github.com/brownplt/LambdaS5/blob/master/src/ljs/ljs_eval.ml#L272, the value to be “assigned” is stored in v_value, but this variable is only used for Data fields, and never for Accessor ones…