diff --git a/src/expr/linkplan.rs b/src/expr/linkplan.rs
index a98432c..9a4739b 100644
--- a/src/expr/linkplan.rs
+++ b/src/expr/linkplan.rs
@@ -50,9 +50,8 @@ fn calculate_votes(mut que: Vec<Box<[u8]>>) -> Vec<BTreeMap<Box<[u8]>, VoteEntry
         .take(que.iter().map(|i| sum(&i[..])).max().map(|i| i.checked_add(1).unwrap()).unwrap_or(0))
         .collect::<Vec<BTreeMap<Box<[u8]>, VoteEntry>>>();
 
-    for i in core::mem::replace(&mut que, Vec::new()) {
-        let mut l = &mut levels[sum(&i[..])];
-        l.insert(i, VoteEntry {
+    for i in core::mem::take(&mut que) {
+        levels[sum(&i[..])].insert(i, VoteEntry {
             votes: 1,
             best_parent: 0,
             is_used: true,
@@ -62,9 +61,9 @@ fn calculate_votes(mut que: Vec<Box<[u8]>>) -> Vec<BTreeMap<Box<[u8]>, VoteEntry
     // process levels (start from largest)
     for (lid, i) in levels.iter_mut().enumerate().rev() {
         // insert queued items into this level
-        for j in core::mem::replace(&mut que, Vec::new()) {
-            let mut v = i.entry(j).or_default();
-            v.votes = v.votes.checked_add(1).unwrap();
+        for j in core::mem::take(&mut que) {
+            let votes = &mut i.entry(j).or_default().votes;
+            *votes = votes.checked_add(1).unwrap();
         }
 
         // handle all items in this level
@@ -138,9 +137,9 @@ pub fn fullfill_links(que: Vec<Link>) -> Vec<Vec<Vec<(Box<[u8]>, u16)>>> {
     let mut ret = vec![Vec::new(); max_vid];
 
     for (vid, que) in g {
-        let mut votes = calculate_votes(que.clone());
-        let mut ret = &mut ret[usize::from(vid)];
-        ret.resize_with(votes.len(), || Vec::new());
+        let votes = calculate_votes(que.clone());
+        let ret = &mut ret[usize::from(vid)];
+        ret.resize_with(votes.len(), Vec::new);
 
         for (i, j) in ret.iter_mut().zip(votes.into_iter()) {
             for (k, l) in j.into_iter() {
diff --git a/src/expr/mod.rs b/src/expr/mod.rs
index 7a2ce6d..7397b19 100644
--- a/src/expr/mod.rs
+++ b/src/expr/mod.rs
@@ -104,7 +104,7 @@ impl System {
 #[derive(Clone, Debug, PartialEq, thiserror::Error)]
 pub enum ParseError {
     #[error("unexpected end of expression")]
-    EmptyExpr,
+    UnexpectedEol,
 
     #[error("unexpected invalid char '{0}'")]
     InvalidChar(char),
@@ -131,14 +131,14 @@ pub enum ParseError {
     Float(#[from] std::num::ParseFloatError),
 }
 
-trait ParseLink: Sized {
+pub trait ParseLink: Sized {
     fn parse_link(slb: &mut StrLexerBase<'_>) -> Result<Option<Self>, ParseError>;
 }
 
 impl ParseLink for () {
     fn parse_link(slb: &mut StrLexerBase<'_>) -> Result<Option<Self>, ParseError> {
         if slb.inp.is_empty() {
-            Err(ParseError::EmptyExpr)
+            Err(ParseError::UnexpectedEol)
         } else if slb.inp.starts_with('.') {
             slb.consume(1);
             Ok(Some(()))
@@ -151,9 +151,9 @@ impl ParseLink for () {
 impl ParseLink for Link {
     fn parse_link(slb: &mut StrLexerBase<'_>) -> Result<Option<Self>, ParseError> {
         if slb.inp.is_empty() {
-            Err(ParseError::EmptyExpr)
+            Err(ParseError::UnexpectedEol)
         } else {
-            let mut new_slb = (*slb).clone();
+            let mut new_slb = *slb;
             let var = new_slb.consume_select(|i| i.is_ascii_digit());
             if var.is_empty() {
                 return Ok(None);
@@ -188,7 +188,7 @@ fn parse_expr<L: Clone + ParseLink>(slb: &mut StrLexerBase<'_>) -> Result<Expr<L
 
     if slb.inp.starts_with(|i: char| i == '-' || i.is_ascii_digit()) {
         // float
-        let mut new_slb = (*slb).clone();
+        let mut new_slb = *slb;
 
         let neg = new_slb.inp.bytes().next() == Some(b'-');
         if neg {
@@ -205,7 +205,7 @@ fn parse_expr<L: Clone + ParseLink>(slb: &mut StrLexerBase<'_>) -> Result<Expr<L
 
     let ident = slb.consume_select(|i| i.is_ascii_alphanumeric());
     if slb.inp.is_empty() {
-        return Err(ParseError::EmptyExpr);
+        return Err(ParseError::UnexpectedEol);
     }
     if ident.is_empty() {
         let c = slb.inp.chars().next().unwrap();
@@ -213,7 +213,7 @@ fn parse_expr<L: Clone + ParseLink>(slb: &mut StrLexerBase<'_>) -> Result<Expr<L
     }
 
     // parse nesting...
-    if slb.inp.chars().next() != Some('(') {
+    if !slb.inp.starts_with('(') {
         let c = slb.inp.chars().next().unwrap();
         return Err(ParseError::InvalidChar(c));
     }
@@ -223,13 +223,17 @@ fn parse_expr<L: Clone + ParseLink>(slb: &mut StrLexerBase<'_>) -> Result<Expr<L
     loop {
         args.push(parse_expr::<L>(slb)?);
         slb.consume_select(|i| i.is_whitespace());
-        if slb.inp.chars().next() != Some(',') {
+        if !slb.inp.starts_with(',') {
             break;
         }
         slb.consume(1);
     }
 
-    if slb.inp.chars().next() != Some(')') {
+    if slb.inp.is_empty() {
+        return Err(ParseError::UnexpectedEol);
+    }
+
+    if !slb.inp.starts_with(')') {
         let c = slb.inp.chars().next().unwrap();
         return Err(ParseError::InvalidChar(c));
     }
diff --git a/src/main.rs b/src/main.rs
index a8e4291..526dc0e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -42,7 +42,7 @@ fn main() {
     // parse system
     let system = {
         let system = std::fs::read(&cli.system).expect("unable to read system to render");
-        let system = std::str::from_utf8(&*system).expect("unable to interpret system description as UTF-8");
+        let system = std::str::from_utf8(&system).expect("unable to interpret system description as UTF-8");
         expr::parse_system(system).expect("unable to parse system")
     };
 
diff --git a/src/mesh/grid.rs b/src/mesh/grid.rs
index b08eedd..2eab7c4 100644
--- a/src/mesh/grid.rs
+++ b/src/mesh/grid.rs
@@ -21,13 +21,12 @@ impl<F: FnMut(&[u16])> ForEachStencilData<'_, F> {
         let prefix: usize = self.buf.len().checked_sub(shape.len()).expect("buffer too small");
 
         // recurse over `this`
-        if let Some(&fi) = shape.get(0) {
+        if let Some(&fi) = shape.first() {
             let shnext = &shape[1..];
             for i in self.stencil_start .. (fi + 1 - self.stencil_end) {
                 self.buf[prefix] = i;
                 self.fe_st_intern(shnext);
             }
-            return;
         } else {
             (*self.f)(self.buf);
         }
@@ -68,7 +67,7 @@ impl Shape {
                     return None;
                 }
                 // (v, acc) = (x % s, x / s)
-                Some(acc.checked_mul(s)?.checked_add(v)?)
+                acc.checked_mul(s)?.checked_add(v)
             })
     }