diff --git a/src/validator.rs b/src/validator.rs
index 7b9698a..2340c42 100644
--- a/src/validator.rs
+++ b/src/validator.rs
@@ -1,5 +1,5 @@
 use crate::parser::*;
-use crate::spans::Span;
+use crate::spans::{Span, Spanned};
 use crate::value::Value;
 use std::collections::{HashMap, HashSet};
 
@@ -143,6 +143,13 @@ impl<'a> Validator<'a> {
         }
     }
 
+    fn visit(&mut self, node: &'a Spanned<Ast>) {
+        let (expr, span) = node;
+        self.ast = expr;
+        self.span = *span;
+        self.validate();
+    }
+
     pub fn validate(&mut self) {
         use Ast::*;
         let root = self.ast;
@@ -179,18 +186,13 @@ impl<'a> Validator<'a> {
                 }
                 let to = self.locals.len();
                 let tailpos = self.status.tail_position;
-                for (expr, span) in block.iter().take(block.len() - 1) {
+                for line in block.iter().take(block.len() - 1) {
                     self.status.tail_position = false;
-                    self.ast = expr;
-                    self.span = *span;
-                    self.validate();
+                    self.visit(line);
                 }
 
-                let (expr, span) = block.last().unwrap();
-                self.ast = expr;
-                self.span = *span;
                 self.status.tail_position = tailpos;
-                self.validate();
+                self.visit(block.last().unwrap());
 
                 let block_bindings = self.locals.split_off(to);
 
@@ -207,22 +209,12 @@ impl<'a> Validator<'a> {
                 let tailpos = self.status.tail_position;
                 self.status.tail_position = false;
 
-                let (expr, span) = cond.as_ref();
-                self.ast = expr;
-                self.span = *span;
-                self.validate();
+                self.visit(cond.as_ref());
 
                 // pass through tailpos only to then/else
                 self.status.tail_position = tailpos;
-                let (expr, span) = then.as_ref();
-                self.ast = expr;
-                self.span = *span;
-                self.validate();
-
-                let (expr, span) = r#else.as_ref();
-                self.ast = expr;
-                self.span = *span;
-                self.validate();
+                self.visit(then.as_ref());
+                self.visit(r#else.as_ref());
             }
             Tuple(members) => {
                 if members.is_empty() {
@@ -230,10 +222,8 @@ impl<'a> Validator<'a> {
                 }
                 let tailpos = self.status.tail_position;
                 self.status.tail_position = false;
-                for (expr, span) in members {
-                    self.ast = expr;
-                    self.span = *span;
-                    self.validate();
+                for member in members {
+                    self.visit(member);
                 }
                 self.status.tail_position = tailpos;
             }
@@ -244,10 +234,8 @@ impl<'a> Validator<'a> {
                 }
                 let tailpos = self.status.tail_position;
                 self.status.tail_position = false;
-                for (expr, span) in args {
-                    self.ast = expr;
-                    self.span = *span;
-                    self.validate();
+                for arg in args {
+                    self.visit(arg);
                 }
                 self.status.has_placeholder = false;
                 self.status.tail_position = tailpos;
@@ -267,30 +255,21 @@ impl<'a> Validator<'a> {
                 }
                 let tailpos = self.status.tail_position;
                 self.status.tail_position = false;
-                for (expr, span) in list {
-                    self.ast = expr;
-                    self.span = *span;
-                    self.validate();
+                for member in list {
+                    self.visit(member);
                 }
 
                 self.status.tail_position = tailpos;
             }
-            Pair(_, value) => {
-                let (expr, span) = value.as_ref();
-                self.ast = expr;
-                self.span = *span;
-                self.validate();
-            }
+            Pair(_, value) => self.visit(value.as_ref()),
             Dict(dict) => {
                 if dict.is_empty() {
                     return;
                 }
                 let tailpos = self.status.tail_position;
                 self.status.tail_position = false;
-                for (expr, span) in dict {
-                    self.ast = expr;
-                    self.span = *span;
-                    self.validate();
+                for pair in dict {
+                    self.visit(pair)
                 }
                 self.status.tail_position = tailpos;
             }
@@ -299,31 +278,16 @@ impl<'a> Validator<'a> {
             // check arity against fn info if first term is word and second term is args
             Synthetic(first, second, rest) => {
                 match (&first.0, &second.0) {
-                    (Ast::Word(_), Ast::Keyword(_)) => {
-                        let (expr, span) = first.as_ref();
-                        self.ast = expr;
-                        self.span = *span;
-                        self.validate();
-                    }
+                    (Ast::Word(_), Ast::Keyword(_)) => self.visit(first.as_ref()),
                     (Ast::Keyword(_), Ast::Arguments(args)) => {
                         if args.len() != 1 {
                             self.err("called keywords may only take one argument".to_string())
                         }
-                        let (expr, span) = second.as_ref();
-                        self.ast = expr;
-                        self.span = *span;
-                        self.validate();
+                        self.visit(second.as_ref());
                     }
                     (Ast::Word(name), Ast::Arguments(args)) => {
-                        let (expr, span) = first.as_ref();
-                        self.ast = expr;
-                        self.span = *span;
-                        self.validate();
-
-                        let (expr, span) = second.as_ref();
-                        self.ast = expr;
-                        self.span = *span;
-                        self.validate();
+                        self.visit(first.as_ref());
+                        self.visit(second.as_ref());
 
                         //TODO: check arities of prelude fns, too
                         let fn_binding = self.bound(name);
@@ -337,32 +301,20 @@ impl<'a> Validator<'a> {
                     _ => unreachable!(),
                 }
                 for term in rest {
-                    let (expr, span) = term;
-                    self.ast = expr;
-                    self.span = *span;
-                    self.validate();
+                    self.visit(term);
                 }
             }
             WhenClause(cond, body) => {
                 let tailpos = self.status.tail_position;
                 self.status.tail_position = false;
-                let (expr, span) = cond.as_ref();
-                self.ast = expr;
-                self.span = *span;
-                self.validate();
-
+                self.visit(cond.as_ref());
+                //pass through tail position for when bodies
                 self.status.tail_position = tailpos;
-                let (expr, span) = body.as_ref();
-                self.ast = expr;
-                self.span = *span;
-                self.validate();
+                self.visit(body.as_ref());
             }
             When(clauses) => {
                 for clause in clauses {
-                    let (expr, span) = clause;
-                    self.ast = expr;
-                    self.span = *span;
-                    self.validate();
+                    self.visit(clause);
                 }
             }
 
@@ -374,54 +326,30 @@ impl<'a> Validator<'a> {
                 } else {
                     self.bind(name.to_string());
                 }
-                let (expr, span) = boxed.as_ref();
-                self.ast = expr;
-                self.span = *span;
-                self.validate();
+                self.visit(boxed.as_ref());
             }
             Let(lhs, rhs) => {
-                let (expr, span) = rhs.as_ref();
-                self.ast = expr;
-                self.span = *span;
-                self.validate();
-
-                let (expr, span) = lhs.as_ref();
-                self.ast = expr;
-                self.span = *span;
-                self.validate();
+                self.visit(rhs.as_ref());
+                self.visit(lhs.as_ref());
             }
             MatchClause(pattern, guard, body) => {
                 let to = self.locals.len();
 
-                let (patt, span) = pattern.as_ref();
-                self.ast = patt;
-                self.span = *span;
-                self.validate();
+                self.visit(pattern.as_ref());
 
-                if let Some((expr, span)) = guard.as_ref() {
-                    self.ast = expr;
-                    self.span = *span;
-                    self.validate();
+                if let Some(guard) = guard.as_ref() {
+                    self.visit(guard);
                 }
 
-                let (expr, span) = body.as_ref();
-                self.ast = expr;
-                self.span = *span;
-                self.validate();
+                self.visit(body.as_ref());
 
                 self.locals.truncate(to);
             }
             Match(scrutinee, clauses) => {
-                let (expr, span) = scrutinee.as_ref();
-                self.ast = expr;
-                self.span = *span;
-                self.validate();
+                self.visit(scrutinee.as_ref());
 
                 for clause in clauses {
-                    let (expr, span) = clause;
-                    self.ast = expr;
-                    self.span = *span;
-                    self.validate();
+                    self.visit(clause);
                 }
             }
             FnDeclaration(name) => {
@@ -488,10 +416,7 @@ impl<'a> Validator<'a> {
             Panic(msg) => {
                 let tailpos = self.status.tail_position;
                 self.status.tail_position = false;
-                let (expr, span) = msg.as_ref();
-                self.ast = expr;
-                self.span = *span;
-                self.validate();
+                self.visit(msg.as_ref());
                 self.status.tail_position = tailpos;
             }
             // TODO: fix the tail call here?
@@ -500,39 +425,23 @@ impl<'a> Validator<'a> {
                     return self.err("do expressions must have at least two terms".to_string());
                 }
                 for term in terms.iter().take(terms.len() - 1) {
-                    let (expr, span) = term;
-                    self.ast = expr;
-                    self.span = *span;
-                    self.validate();
+                    self.visit(term);
                 }
-
-                let (expr, span) = terms.last().unwrap();
-                self.ast = expr;
-                self.span = *span;
-                if matches!(expr, Ast::Recur(_)) {
+                let last = terms.last().unwrap();
+                self.visit(last);
+                if matches!(last.0, Ast::Recur(_)) {
                     self.err("`recur` may not be used in `do` forms".to_string());
                 }
-                self.validate();
             }
             Repeat(times, body) => {
                 self.status.tail_position = false;
-                let (expr, span) = times.as_ref();
-                self.ast = expr;
-                self.span = *span;
-                self.validate();
-
-                let (expr, span) = body.as_ref();
-                self.ast = expr;
-                self.span = *span;
-                self.validate();
+                self.visit(times.as_ref());
+                self.visit(body.as_ref());
             }
             Loop(with, body) => {
-                let (expr, span) = with.as_ref();
-                self.span = *span;
-                self.ast = expr;
-                self.validate();
+                self.visit(with.as_ref());
 
-                let Ast::Tuple(input) = expr else {
+                let Ast::Tuple(input) = &with.0 else {
                     unreachable!()
                 };
 
@@ -588,10 +497,7 @@ impl<'a> Validator<'a> {
 
                 self.status.tail_position = false;
                 for arg in args {
-                    let (expr, span) = arg;
-                    self.ast = expr;
-                    self.span = *span;
-                    self.validate();
+                    self.visit(arg);
                 }
             }
             WordPattern(name) => match self.bound(name) {
@@ -654,25 +560,15 @@ impl<'a> Validator<'a> {
                     return;
                 }
                 for term in terms.iter().take(terms.len() - 1) {
-                    let (patt, span) = term;
-                    self.ast = patt;
-                    self.span = *span;
-                    self.validate();
+                    self.visit(term);
                 }
 
                 self.status.last_term = true;
-                let (patt, span) = terms.last().unwrap();
-                self.ast = patt;
-                self.span = *span;
-                self.validate();
+                let last = terms.last().unwrap();
+                self.visit(last);
                 self.status.last_term = false;
             }
-            PairPattern(_, patt) => {
-                let (patt, span) = patt.as_ref();
-                self.ast = patt;
-                self.span = *span;
-                self.validate();
-            }
+            PairPattern(_, patt) => self.visit(patt.as_ref()),
             // terminals can never be invalid
             Nil | Boolean(_) | Number(_) | Keyword(_) | String(_) => (),
             // terminal patterns can never be invalid