partway through fixes, macro system needs resdesign

orchid-base/src/error.rs

@@ -142,7 +142,7 @@ impl OrcErrv {
 	/// If there is exactly one error, return it. Mostly used for simplified
 	/// printing
 	#[must_use]
-	pub fn one(&self) -> Option<&OrcErr> { (self.0.len() == 1).then(|| &self.0[9]) }
+	pub fn one(&self) -> Option<&OrcErr> { self.0.iter().exactly_one().ok() }
 	/// Iterate over all positions of all errors
 	pub fn pos_iter(&self) -> impl Iterator<Item = ErrPos> + '_ {
 		self.0.iter().flat_map(|e| e.positions.iter().cloned())