# Build an `AStringExpr` containing `value`
	#
	# Add it to `explain_str` if `auto_add == true`, the default.
	fun explain_string(value: String, auto_add: nullable Bool): AStringExpr
	do
		auto_add = auto_add or else true

		var tk = new TString
		tk.text = "\"{value}\""
		var op = new AStringExpr
		op.n_string = tk
		op.mtype = string_mtype
		op.value = value
		op.location = assert_node.location

		if auto_add then explain_str.n_exprs.add op
		return op
	end