From 6ae6d86b9c6fefe6c5379ac1b20ea90634c09c81 Mon Sep 17 00:00:00 2001
From: Laurenz <laurmaedje@gmail.com>
Date: Sat, 14 Aug 2021 15:24:59 +0200
Subject: [PATCH] Separate type for string values

---
 src/eval/array.rs          |  39 ++++----
 src/eval/dict.rs           |  70 ++++++++------
 src/eval/function.rs       |  72 ++++++++++----
 src/eval/mod.rs            |  46 +++++----
 src/eval/scope.rs          |   4 +-
 src/eval/str.rs            | 137 ++++++++++++++++++++++++++
 src/eval/template.rs       |  50 +++++-----
 src/eval/value.rs          | 132 +++++++++++++++++++------
 src/exec/mod.rs            |   7 +-
 src/layout/grid.rs         |   2 +-
 src/layout/stack.rs        |   2 +-
 src/lib.rs                 |   1 -
 src/library/elements.rs    |  12 +--
 src/library/layout.rs      |  24 ++---
 src/library/mod.rs         |   3 +-
 src/library/text.rs        |  18 ++--
 src/library/utility.rs     |  44 ++++-----
 src/parse/resolve.rs       |   6 +-
 src/parse/tokens.rs        |  10 +-
 src/syntax/ident.rs        |   7 +-
 src/syntax/mod.rs          |   2 +
 src/{ => syntax}/pretty.rs | 191 ++-----------------------------------
 src/syntax/span.rs         |  24 ++---
 src/util/eco.rs            | 188 ++++++++++++++----------------------
 tests/typ/utility/math.typ |   2 +-
 25 files changed, 565 insertions(+), 528 deletions(-)
 create mode 100644 src/eval/str.rs
 rename src/{ => syntax}/pretty.rs (74%)

diff --git a/src/eval/array.rs b/src/eval/array.rs
index 356aa0ca9..ec8f46d37 100644
--- a/src/eval/array.rs
+++ b/src/eval/array.rs
@@ -1,5 +1,5 @@
 use std::convert::TryFrom;
-use std::fmt::{self, Debug, Formatter};
+use std::fmt::{self, Debug, Display, Formatter, Write};
 use std::iter::FromIterator;
 use std::ops::{Add, AddAssign};
 use std::rc::Rc;
@@ -19,8 +19,8 @@ macro_rules! array {
     };
 }
 
-/// A variably-typed array with clone-on-write value semantics.
-#[derive(Clone, PartialEq)]
+/// An array of values with clone-on-write value semantics.
+#[derive(Default, Clone, PartialEq)]
 pub struct Array {
     vec: Rc<Vec<Value>>,
 }
@@ -28,7 +28,7 @@ pub struct Array {
 impl Array {
     /// Create a new, empty array.
     pub fn new() -> Self {
-        Self { vec: Rc::new(vec![]) }
+        Self::default()
     }
 
     /// Create a new array from a vector of values.
@@ -36,16 +36,9 @@ impl Array {
         Self { vec: Rc::new(vec) }
     }
 
-    /// Create a new, empty array with the given `capacity`.
-    pub fn with_capacity(capacity: usize) -> Self {
-        Self {
-            vec: Rc::new(Vec::with_capacity(capacity)),
-        }
-    }
-
     /// Whether the array is empty.
     pub fn is_empty(&self) -> bool {
-        self.len() == 0
+        self.vec.is_empty()
     }
 
     /// The length of the array.
@@ -106,18 +99,28 @@ fn out_of_bounds(index: i64, len: i64) -> String {
     format!("array index out of bounds (index: {}, len: {})", index, len)
 }
 
-impl Default for Array {
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
 impl Debug for Array {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         f.debug_list().entries(self.vec.iter()).finish()
     }
 }
 
+impl Display for Array {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        f.write_char('(')?;
+        for (i, value) in self.iter().enumerate() {
+            Display::fmt(value, f)?;
+            if i + 1 < self.vec.len() {
+                f.write_str(", ")?;
+            }
+        }
+        if self.len() == 1 {
+            f.write_char(',')?;
+        }
+        f.write_char(')')
+    }
+}
+
 impl Add for Array {
     type Output = Self;
 
diff --git a/src/eval/dict.rs b/src/eval/dict.rs
index 730392dc8..e71d0c6a0 100644
--- a/src/eval/dict.rs
+++ b/src/eval/dict.rs
@@ -1,13 +1,11 @@
 use std::collections::BTreeMap;
-use std::fmt::{self, Debug, Formatter};
+use std::fmt::{self, Debug, Display, Formatter, Write};
 use std::iter::FromIterator;
 use std::ops::{Add, AddAssign};
 use std::rc::Rc;
 
-use super::Value;
+use super::{Str, Value};
 use crate::diag::StrResult;
-use crate::pretty::pretty;
-use crate::util::EcoString;
 
 /// Create a new [`Dict`] from key-value pairs.
 #[allow(unused_macros)]
@@ -15,15 +13,15 @@ macro_rules! dict {
     ($($key:expr => $value:expr),* $(,)?) => {{
         #[allow(unused_mut)]
         let mut map = std::collections::BTreeMap::new();
-        $(map.insert($crate::util::EcoString::from($key), $crate::eval::Value::from($value));)*
+        $(map.insert($crate::eval::Str::from($key), $crate::eval::Value::from($value));)*
         $crate::eval::Dict::from_map(map)
     }};
 }
 
-/// A variably-typed dictionary with clone-on-write value semantics.
-#[derive(Clone, PartialEq)]
+/// A dictionary from strings to values with clone-on-write value semantics.
+#[derive(Default, Clone, PartialEq)]
 pub struct Dict {
-    map: Rc<BTreeMap<EcoString, Value>>,
+    map: Rc<BTreeMap<Str, Value>>,
 }
 
 impl Dict {
@@ -33,13 +31,13 @@ impl Dict {
     }
 
     /// Create a new dictionary from a mapping of strings to values.
-    pub fn from_map(map: BTreeMap<EcoString, Value>) -> Self {
+    pub fn from_map(map: BTreeMap<Str, Value>) -> Self {
         Self { map: Rc::new(map) }
     }
 
     /// Whether the dictionary is empty.
     pub fn is_empty(&self) -> bool {
-        self.len() == 0
+        self.map.is_empty()
     }
 
     /// The number of pairs in the dictionary.
@@ -48,21 +46,21 @@ impl Dict {
     }
 
     /// Borrow the value the given `key` maps to.
-    pub fn get(&self, key: &str) -> StrResult<&Value> {
-        self.map.get(key).ok_or_else(|| missing_key(key))
+    pub fn get(&self, key: Str) -> StrResult<&Value> {
+        self.map.get(&key).ok_or_else(|| missing_key(&key))
     }
 
     /// Mutably borrow the value the given `key` maps to.
     ///
     /// This inserts the key with [`None`](Value::None) as the value if not
     /// present so far.
-    pub fn get_mut(&mut self, key: EcoString) -> &mut Value {
-        Rc::make_mut(&mut self.map).entry(key).or_default()
+    pub fn get_mut(&mut self, key: Str) -> &mut Value {
+        Rc::make_mut(&mut self.map).entry(key.into()).or_default()
     }
 
     /// Insert a mapping from the given `key` to the given `value`.
-    pub fn insert(&mut self, key: EcoString, value: Value) {
-        Rc::make_mut(&mut self.map).insert(key, value);
+    pub fn insert(&mut self, key: Str, value: Value) {
+        Rc::make_mut(&mut self.map).insert(key.into(), value);
     }
 
     /// Clear the dictionary.
@@ -75,20 +73,32 @@ impl Dict {
     }
 
     /// Iterate over pairs of references to the contained keys and values.
-    pub fn iter(&self) -> std::collections::btree_map::Iter<EcoString, Value> {
+    pub fn iter(&self) -> std::collections::btree_map::Iter<Str, Value> {
         self.map.iter()
     }
 }
 
 /// The missing key access error message.
 #[cold]
-fn missing_key(key: &str) -> String {
-    format!("dictionary does not contain key: {}", pretty(key))
+fn missing_key(key: &Str) -> String {
+    format!("dictionary does not contain key: {}", key)
 }
 
-impl Default for Dict {
-    fn default() -> Self {
-        Self::new()
+impl Display for Dict {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        f.write_char('(')?;
+        if self.is_empty() {
+            f.write_char(':')?;
+        }
+        for (i, (key, value)) in self.iter().enumerate() {
+            f.write_str(key)?;
+            f.write_str(": ")?;
+            Display::fmt(value, f)?;
+            if i + 1 < self.map.len() {
+                f.write_str(", ")?;
+            }
+        }
+        f.write_char(')')
     }
 }
 
@@ -116,21 +126,21 @@ impl AddAssign for Dict {
     }
 }
 
-impl FromIterator<(EcoString, Value)> for Dict {
-    fn from_iter<T: IntoIterator<Item = (EcoString, Value)>>(iter: T) -> Self {
+impl FromIterator<(Str, Value)> for Dict {
+    fn from_iter<T: IntoIterator<Item = (Str, Value)>>(iter: T) -> Self {
         Dict { map: Rc::new(iter.into_iter().collect()) }
     }
 }
 
-impl Extend<(EcoString, Value)> for Dict {
-    fn extend<T: IntoIterator<Item = (EcoString, Value)>>(&mut self, iter: T) {
+impl Extend<(Str, Value)> for Dict {
+    fn extend<T: IntoIterator<Item = (Str, Value)>>(&mut self, iter: T) {
         Rc::make_mut(&mut self.map).extend(iter);
     }
 }
 
 impl IntoIterator for Dict {
-    type Item = (EcoString, Value);
-    type IntoIter = std::collections::btree_map::IntoIter<EcoString, Value>;
+    type Item = (Str, Value);
+    type IntoIter = std::collections::btree_map::IntoIter<Str, Value>;
 
     fn into_iter(self) -> Self::IntoIter {
         match Rc::try_unwrap(self.map) {
@@ -141,8 +151,8 @@ impl IntoIterator for Dict {
 }
 
 impl<'a> IntoIterator for &'a Dict {
-    type Item = (&'a EcoString, &'a Value);
-    type IntoIter = std::collections::btree_map::Iter<'a, EcoString, Value>;
+    type Item = (&'a Str, &'a Value);
+    type IntoIter = std::collections::btree_map::Iter<'a, Str, Value>;
 
     fn into_iter(self) -> Self::IntoIter {
         self.iter()
diff --git a/src/eval/function.rs b/src/eval/function.rs
index 550db59df..f18af05eb 100644
--- a/src/eval/function.rs
+++ b/src/eval/function.rs
@@ -1,15 +1,17 @@
-use std::fmt::{self, Debug, Formatter};
+use std::fmt::{self, Debug, Display, Formatter, Write};
 use std::ops::Deref;
 use std::rc::Rc;
 
-use super::{Cast, EvalContext, Value};
+use super::{Cast, EvalContext, Str, Value};
 use crate::diag::{At, TypResult};
 use crate::syntax::{Span, Spanned};
 use crate::util::EcoString;
 
 /// An evaluatable function.
 #[derive(Clone)]
-pub struct Function(Rc<Repr<Func>>);
+pub struct Function {
+    repr: Rc<Repr<Func>>,
+}
 
 /// The unsized representation behind the [`Rc`].
 struct Repr<T: ?Sized> {
@@ -17,20 +19,20 @@ struct Repr<T: ?Sized> {
     func: T,
 }
 
-type Func = dyn Fn(&mut EvalContext, &mut FuncArgs) -> TypResult<Value>;
+type Func = dyn Fn(&mut EvalContext, &mut Arguments) -> TypResult<Value>;
 
 impl Function {
     /// Create a new function from a rust closure.
     pub fn new<F>(name: Option<EcoString>, func: F) -> Self
     where
-        F: Fn(&mut EvalContext, &mut FuncArgs) -> TypResult<Value> + 'static,
+        F: Fn(&mut EvalContext, &mut Arguments) -> TypResult<Value> + 'static,
     {
-        Self(Rc::new(Repr { name, func }))
+        Self { repr: Rc::new(Repr { name, func }) }
     }
 
     /// The name of the function.
     pub fn name(&self) -> Option<&EcoString> {
-        self.0.name.as_ref()
+        self.repr.name.as_ref()
     }
 }
 
@@ -38,44 +40,55 @@ impl Deref for Function {
     type Target = Func;
 
     fn deref(&self) -> &Self::Target {
-        &self.0.func
+        &self.repr.func
+    }
+}
+
+impl Display for Function {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        f.write_str("<function")?;
+        if let Some(name) = self.name() {
+            f.write_char(' ')?;
+            f.write_str(name)?;
+        }
+        f.write_char('>')
     }
 }
 
 impl Debug for Function {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        f.debug_struct("ValueFunc").field("name", &self.0.name).finish()
+        f.debug_struct("Function").field("name", &self.repr.name).finish()
     }
 }
 
 impl PartialEq for Function {
     fn eq(&self, other: &Self) -> bool {
         // We cast to thin pointers for comparison.
-        Rc::as_ptr(&self.0) as *const () == Rc::as_ptr(&other.0) as *const ()
+        Rc::as_ptr(&self.repr) as *const () == Rc::as_ptr(&other.repr) as *const ()
     }
 }
 
 /// Evaluated arguments to a function.
 #[derive(Debug, Clone, PartialEq)]
-pub struct FuncArgs {
+pub struct Arguments {
     /// The span of the whole argument list.
     pub span: Span,
     /// The positional and named arguments.
-    pub items: Vec<FuncArg>,
+    pub items: Vec<Argument>,
 }
 
 /// An argument to a function call: `12` or `draw: false`.
 #[derive(Debug, Clone, PartialEq)]
-pub struct FuncArg {
+pub struct Argument {
     /// The span of the whole argument.
     pub span: Span,
     /// The name of the argument (`None` for positional arguments).
-    pub name: Option<EcoString>,
+    pub name: Option<Str>,
     /// The value of the argument.
     pub value: Spanned<Value>,
 }
 
-impl FuncArgs {
+impl Arguments {
     /// Find and consume the first castable positional argument.
     pub fn eat<T>(&mut self) -> Option<T>
     where
@@ -150,16 +163,14 @@ impl FuncArgs {
         }
         Ok(())
     }
-}
 
-impl FuncArgs {
     /// Reinterpret these arguments as actually being an array index.
     pub fn into_index(self) -> TypResult<i64> {
         self.into_castable("index")
     }
 
     /// Reinterpret these arguments as actually being a dictionary key.
-    pub fn into_key(self) -> TypResult<EcoString> {
+    pub fn into_key(self) -> TypResult<Str> {
         self.into_castable("key")
     }
 
@@ -170,11 +181,11 @@ impl FuncArgs {
     {
         let mut iter = self.items.into_iter();
         let value = match iter.next() {
-            Some(FuncArg { name: None, value, .. }) => value.v.cast().at(value.span)?,
+            Some(Argument { name: None, value, .. }) => value.v.cast().at(value.span)?,
             None => {
                 bail!(self.span, "missing {}", what);
             }
-            Some(FuncArg { name: Some(_), span, .. }) => {
+            Some(Argument { name: Some(_), span, .. }) => {
                 bail!(span, "named pair is not allowed here");
             }
         };
@@ -186,3 +197,24 @@ impl FuncArgs {
         Ok(value)
     }
 }
+
+impl Display for Arguments {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        f.write_char('(')?;
+        for (i, arg) in self.items.iter().enumerate() {
+            if let Some(name) = &arg.name {
+                f.write_str(name)?;
+                f.write_str(": ")?;
+            }
+            Display::fmt(&arg.value.v, f)?;
+            if i + 1 < self.items.len() {
+                f.write_str(", ")?;
+            }
+        }
+        f.write_char(')')
+    }
+}
+
+dynamic! {
+    Arguments: "arguments",
+}
diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index 9e6fad8fd..30b34798d 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -10,8 +10,10 @@ mod capture;
 mod function;
 mod ops;
 mod scope;
+mod str;
 mod template;
 
+pub use self::str::*;
 pub use array::*;
 pub use capture::*;
 pub use dict::*;
@@ -35,7 +37,7 @@ use crate::parse::parse;
 use crate::source::{SourceId, SourceStore};
 use crate::syntax::visit::Visit;
 use crate::syntax::*;
-use crate::util::{EcoString, RefMutExt};
+use crate::util::RefMutExt;
 use crate::Context;
 
 /// Evaluate a parsed source file into a module.
@@ -214,7 +216,7 @@ impl Eval for Lit {
             Self::Angle(_, v, unit) => Value::Angle(Angle::with_unit(v, unit)),
             Self::Percent(_, v) => Value::Relative(Relative::new(v / 100.0)),
             Self::Fractional(_, v) => Value::Fractional(Fractional::new(v)),
-            Self::Str(_, ref v) => Value::Str(v.clone()),
+            Self::Str(_, ref v) => Value::Str(v.into()),
         })
     }
 }
@@ -244,7 +246,7 @@ impl Eval for DictExpr {
     fn eval(&self, ctx: &mut EvalContext) -> TypResult<Self::Output> {
         self.items
             .iter()
-            .map(|Named { name, expr }| Ok((name.string.clone(), expr.eval(ctx)?)))
+            .map(|Named { name, expr }| Ok(((&name.string).into(), expr.eval(ctx)?)))
             .collect()
     }
 }
@@ -373,7 +375,7 @@ impl Eval for CallExpr {
             }
 
             Value::Dict(dict) => {
-                dict.get(&args.into_key()?).map(Value::clone).at(self.span)
+                dict.get(args.into_key()?).map(Value::clone).at(self.span)
             }
 
             Value::Func(func) => {
@@ -393,7 +395,7 @@ impl Eval for CallExpr {
 }
 
 impl Eval for CallArgs {
-    type Output = FuncArgs;
+    type Output = Arguments;
 
     fn eval(&self, ctx: &mut EvalContext) -> TypResult<Self::Output> {
         let mut items = Vec::with_capacity(self.items.len());
@@ -402,43 +404,49 @@ impl Eval for CallArgs {
             let span = arg.span();
             match arg {
                 CallArg::Pos(expr) => {
-                    items.push(FuncArg {
+                    items.push(Argument {
                         span,
                         name: None,
                         value: Spanned::new(expr.eval(ctx)?, expr.span()),
                     });
                 }
                 CallArg::Named(Named { name, expr }) => {
-                    items.push(FuncArg {
+                    items.push(Argument {
                         span,
-                        name: Some(name.string.clone()),
+                        name: Some((&name.string).into()),
                         value: Spanned::new(expr.eval(ctx)?, expr.span()),
                     });
                 }
                 CallArg::Spread(expr) => match expr.eval(ctx)? {
-                    Value::Args(args) => {
-                        items.extend(args.items.iter().cloned());
-                    }
                     Value::Array(array) => {
-                        items.extend(array.into_iter().map(|value| FuncArg {
+                        items.extend(array.into_iter().map(|value| Argument {
                             span,
                             name: None,
                             value: Spanned::new(value, span),
                         }));
                     }
                     Value::Dict(dict) => {
-                        items.extend(dict.into_iter().map(|(key, value)| FuncArg {
+                        items.extend(dict.into_iter().map(|(key, value)| Argument {
                             span,
                             name: Some(key),
                             value: Spanned::new(value, span),
                         }));
                     }
-                    v => bail!(expr.span(), "cannot spread {}", v.type_name()),
+                    v => {
+                        if let Value::Dyn(dynamic) = &v {
+                            if let Some(args) = dynamic.downcast_ref::<Arguments>() {
+                                items.extend(args.items.iter().cloned());
+                                continue;
+                            }
+                        }
+
+                        bail!(expr.span(), "cannot spread {}", v.type_name())
+                    }
                 },
             }
         }
 
-        Ok(FuncArgs { span: self.span, items })
+        Ok(Arguments { span: self.span, items })
     }
 }
 
@@ -499,7 +507,7 @@ impl Eval for ClosureExpr {
 
             // Put the remaining arguments into the sink.
             if let Some(sink) = &sink {
-                ctx.scopes.def_mut(sink, Rc::new(args.take()));
+                ctx.scopes.def_mut(sink, args.take());
             }
 
             let value = body.eval(ctx)?;
@@ -599,7 +607,7 @@ impl Eval for ForExpr {
         let iter = self.iter.eval(ctx)?;
         match (&self.pattern, iter) {
             (ForPattern::Value(v), Value::Str(string)) => {
-                iter!(for (v => value) in string.chars().map(|c| Value::Str(c.into())))
+                iter!(for (v => value) in string.iter())
             }
             (ForPattern::Value(v), Value::Array(array)) => {
                 iter!(for (v => value) in array.into_iter())
@@ -627,7 +635,7 @@ impl Eval for ImportExpr {
     type Output = Value;
 
     fn eval(&self, ctx: &mut EvalContext) -> TypResult<Self::Output> {
-        let path = self.path.eval(ctx)?.cast::<EcoString>().at(self.path.span())?;
+        let path = self.path.eval(ctx)?.cast::<Str>().at(self.path.span())?;
 
         let file = ctx.import(&path, self.path.span())?;
         let module = &ctx.modules[&file];
@@ -657,7 +665,7 @@ impl Eval for IncludeExpr {
     type Output = Value;
 
     fn eval(&self, ctx: &mut EvalContext) -> TypResult<Self::Output> {
-        let path = self.path.eval(ctx)?.cast::<EcoString>().at(self.path.span())?;
+        let path = self.path.eval(ctx)?.cast::<Str>().at(self.path.span())?;
 
         let file = ctx.import(&path, self.path.span())?;
         let module = &ctx.modules[&file];
diff --git a/src/eval/scope.rs b/src/eval/scope.rs
index 2eb048fa3..2968ca205 100644
--- a/src/eval/scope.rs
+++ b/src/eval/scope.rs
@@ -4,7 +4,7 @@ use std::fmt::{self, Debug, Formatter};
 use std::iter;
 use std::rc::Rc;
 
-use super::{EvalContext, FuncArgs, Function, Value};
+use super::{Arguments, EvalContext, Function, Value};
 use crate::diag::TypResult;
 use crate::util::EcoString;
 
@@ -91,7 +91,7 @@ impl Scope {
     /// Define a constant function.
     pub fn def_func<F>(&mut self, name: impl Into<EcoString>, f: F)
     where
-        F: Fn(&mut EvalContext, &mut FuncArgs) -> TypResult<Value> + 'static,
+        F: Fn(&mut EvalContext, &mut Arguments) -> TypResult<Value> + 'static,
     {
         let name = name.into();
         self.def_const(name.clone(), Function::new(Some(name), f));
diff --git a/src/eval/str.rs b/src/eval/str.rs
new file mode 100644
index 000000000..7f84f80f1
--- /dev/null
+++ b/src/eval/str.rs
@@ -0,0 +1,137 @@
+use std::convert::TryFrom;
+use std::fmt::{self, Debug, Display, Formatter, Write};
+use std::ops::{Add, AddAssign, Deref};
+
+use crate::diag::StrResult;
+use crate::util::EcoString;
+
+/// A string value with inline storage and clone-on-write semantics.
+#[derive(Default, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
+pub struct Str {
+    string: EcoString,
+}
+
+impl Str {
+    /// Create a new, empty string.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Whether the string is empty.
+    pub fn is_empty(&self) -> bool {
+        self.string.is_empty()
+    }
+
+    /// The length of the string in bytes.
+    pub fn len(&self) -> i64 {
+        self.string.len() as i64
+    }
+
+    /// Borrow this as a string slice.
+    pub fn as_str(&self) -> &str {
+        self.string.as_str()
+    }
+
+    /// Return an iterator over the chars as strings.
+    pub fn iter(&self) -> impl Iterator<Item = Str> + '_ {
+        self.chars().map(Into::into)
+    }
+
+    /// Repeat this string `n` times.
+    pub fn repeat(&self, n: i64) -> StrResult<Self> {
+        let n = usize::try_from(n)
+            .ok()
+            .and_then(|n| self.string.len().checked_mul(n).map(|_| n))
+            .ok_or_else(|| format!("cannot repeat this string {} times", n))?;
+
+        Ok(self.string.repeat(n).into())
+    }
+}
+
+impl Display for Str {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        f.write_char('"')?;
+        for c in self.chars() {
+            match c {
+                '\\' => f.write_str(r"\\")?,
+                '"' => f.write_str(r#"\""#)?,
+                '\n' => f.write_str(r"\n")?,
+                '\r' => f.write_str(r"\r")?,
+                '\t' => f.write_str(r"\t")?,
+                _ => f.write_char(c)?,
+            }
+        }
+        f.write_char('"')
+    }
+}
+
+impl Debug for Str {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        Debug::fmt(&self.string, f)
+    }
+}
+
+impl Deref for Str {
+    type Target = str;
+
+    fn deref(&self) -> &str {
+        self.string.deref()
+    }
+}
+
+impl Add for Str {
+    type Output = Self;
+
+    fn add(mut self, rhs: Self) -> Self::Output {
+        self += rhs;
+        self
+    }
+}
+
+impl AddAssign for Str {
+    fn add_assign(&mut self, rhs: Self) {
+        self.string.push_str(rhs.as_str());
+    }
+}
+
+impl From<char> for Str {
+    fn from(c: char) -> Self {
+        Self { string: c.into() }
+    }
+}
+
+impl From<&str> for Str {
+    fn from(string: &str) -> Self {
+        Self { string: string.into() }
+    }
+}
+
+impl From<String> for Str {
+    fn from(string: String) -> Self {
+        Self { string: string.into() }
+    }
+}
+
+impl From<EcoString> for Str {
+    fn from(string: EcoString) -> Self {
+        Self { string }
+    }
+}
+
+impl From<&EcoString> for Str {
+    fn from(string: &EcoString) -> Self {
+        Self { string: string.clone() }
+    }
+}
+
+impl From<Str> for EcoString {
+    fn from(string: Str) -> Self {
+        string.string
+    }
+}
+
+impl From<&Str> for EcoString {
+    fn from(string: &Str) -> Self {
+        string.string.clone()
+    }
+}
diff --git a/src/eval/template.rs b/src/eval/template.rs
index 4e20b8f8f..594036afb 100644
--- a/src/eval/template.rs
+++ b/src/eval/template.rs
@@ -1,10 +1,10 @@
 use std::collections::HashMap;
 use std::convert::TryFrom;
-use std::fmt::{self, Debug, Formatter};
+use std::fmt::{self, Debug, Display, Formatter};
 use std::ops::{Add, AddAssign, Deref};
 use std::rc::Rc;
 
-use super::Value;
+use super::{Str, Value};
 use crate::diag::StrResult;
 use crate::exec::ExecContext;
 use crate::syntax::{Expr, SyntaxTree};
@@ -40,21 +40,9 @@ impl Template {
     }
 }
 
-impl From<TemplateTree> for Template {
-    fn from(tree: TemplateTree) -> Self {
-        Self::new(vec![TemplateNode::Tree(tree)])
-    }
-}
-
-impl From<TemplateFunc> for Template {
-    fn from(func: TemplateFunc) -> Self {
-        Self::new(vec![TemplateNode::Func(func)])
-    }
-}
-
-impl From<EcoString> for Template {
-    fn from(string: EcoString) -> Self {
-        Self::new(vec![TemplateNode::Str(string)])
+impl Display for Template {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        f.pad("<template>")
     }
 }
 
@@ -83,24 +71,42 @@ impl AddAssign for Template {
     }
 }
 
-impl Add<EcoString> for Template {
+impl Add<Str> for Template {
     type Output = Self;
 
-    fn add(mut self, rhs: EcoString) -> Self::Output {
-        Rc::make_mut(&mut self.nodes).push(TemplateNode::Str(rhs));
+    fn add(mut self, rhs: Str) -> Self::Output {
+        Rc::make_mut(&mut self.nodes).push(TemplateNode::Str(rhs.into()));
         self
     }
 }
 
-impl Add<Template> for EcoString {
+impl Add<Template> for Str {
     type Output = Template;
 
     fn add(self, mut rhs: Template) -> Self::Output {
-        Rc::make_mut(&mut rhs.nodes).insert(0, TemplateNode::Str(self));
+        Rc::make_mut(&mut rhs.nodes).insert(0, TemplateNode::Str(self.into()));
         rhs
     }
 }
 
+impl From<TemplateTree> for Template {
+    fn from(tree: TemplateTree) -> Self {
+        Self::new(vec![TemplateNode::Tree(tree)])
+    }
+}
+
+impl From<TemplateFunc> for Template {
+    fn from(func: TemplateFunc) -> Self {
+        Self::new(vec![TemplateNode::Func(func)])
+    }
+}
+
+impl From<Str> for Template {
+    fn from(string: Str) -> Self {
+        Self::new(vec![TemplateNode::Str(string.into())])
+    }
+}
+
 /// One node of a template.
 ///
 /// Evaluating a template expression creates only a single node. Adding multiple
diff --git a/src/eval/value.rs b/src/eval/value.rs
index 958077da0..62899cc1f 100644
--- a/src/eval/value.rs
+++ b/src/eval/value.rs
@@ -3,7 +3,7 @@ use std::cmp::Ordering;
 use std::fmt::{self, Debug, Display, Formatter};
 use std::rc::Rc;
 
-use super::{ops, Array, Dict, FuncArgs, Function, Template, TemplateFunc};
+use super::{ops, Array, Dict, Function, Str, Template, TemplateFunc};
 use crate::color::{Color, RgbaColor};
 use crate::diag::StrResult;
 use crate::exec::ExecContext;
@@ -37,7 +37,7 @@ pub enum Value {
     /// A color value: `#f79143ff`.
     Color(Color),
     /// A string: `"string"`.
-    Str(EcoString),
+    Str(Str),
     /// An array of values: `(1, "hi", 12cm)`.
     Array(Array),
     /// A dictionary value: `(color: #f79143, pattern: dashed)`.
@@ -48,8 +48,6 @@ pub enum Value {
     Func(Function),
     /// A dynamic value.
     Dyn(Dynamic),
-    /// Captured arguments to a function.
-    Args(Rc<FuncArgs>),
 }
 
 impl Value {
@@ -75,12 +73,11 @@ impl Value {
             Self::Linear(_) => Linear::TYPE_NAME,
             Self::Fractional(_) => Fractional::TYPE_NAME,
             Self::Color(_) => Color::TYPE_NAME,
-            Self::Str(_) => EcoString::TYPE_NAME,
+            Self::Str(_) => Str::TYPE_NAME,
             Self::Array(_) => Array::TYPE_NAME,
             Self::Dict(_) => Dict::TYPE_NAME,
             Self::Template(_) => Template::TYPE_NAME,
             Self::Func(_) => Function::TYPE_NAME,
-            Self::Args(_) => Rc::<FuncArgs>::TYPE_NAME,
             Self::Dyn(v) => v.type_name(),
         }
     }
@@ -102,6 +99,48 @@ impl Value {
     }
 }
 
+impl Default for Value {
+    fn default() -> Self {
+        Value::None
+    }
+}
+
+impl Display for Value {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        match self {
+            Self::None => f.pad("none"),
+            Self::Auto => f.pad("auto"),
+            Self::Bool(v) => Display::fmt(v, f),
+            Self::Int(v) => Display::fmt(v, f),
+            Self::Float(v) => Display::fmt(v, f),
+            Self::Length(v) => Display::fmt(v, f),
+            Self::Angle(v) => Display::fmt(v, f),
+            Self::Relative(v) => Display::fmt(v, f),
+            Self::Linear(v) => Display::fmt(v, f),
+            Self::Fractional(v) => Display::fmt(v, f),
+            Self::Color(v) => Display::fmt(v, f),
+            Self::Str(v) => Display::fmt(v, f),
+            Self::Array(v) => Display::fmt(v, f),
+            Self::Dict(v) => Display::fmt(v, f),
+            Self::Template(v) => Display::fmt(v, f),
+            Self::Func(v) => Display::fmt(v, f),
+            Self::Dyn(v) => Display::fmt(v, f),
+        }
+    }
+}
+
+impl PartialEq for Value {
+    fn eq(&self, other: &Self) -> bool {
+        ops::equal(self, other)
+    }
+}
+
+impl PartialOrd for Value {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        ops::compare(self, other)
+    }
+}
+
 impl From<i32> for Value {
     fn from(v: i32) -> Self {
         Self::Int(v as i64)
@@ -126,6 +165,12 @@ impl From<String> for Value {
     }
 }
 
+impl From<EcoString> for Value {
+    fn from(v: EcoString) -> Self {
+        Self::Str(v.into())
+    }
+}
+
 impl From<RgbaColor> for Value {
     fn from(v: RgbaColor) -> Self {
         Self::Color(Color::Rgba(v))
@@ -137,25 +182,6 @@ impl From<Dynamic> for Value {
         Self::Dyn(v)
     }
 }
-
-impl Default for Value {
-    fn default() -> Self {
-        Value::None
-    }
-}
-
-impl PartialEq for Value {
-    fn eq(&self, other: &Self) -> bool {
-        ops::equal(self, other)
-    }
-}
-
-impl PartialOrd for Value {
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        ops::compare(self, other)
-    }
-}
-
 /// A dynamic value.
 #[derive(Clone)]
 pub struct Dynamic(Rc<dyn Bounds>);
@@ -193,7 +219,7 @@ impl Display for Dynamic {
 
 impl Debug for Dynamic {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        f.debug_tuple("ValueAny").field(&self.0).finish()
+        Debug::fmt(&self.0, f)
     }
 }
 
@@ -332,7 +358,7 @@ macro_rules! dynamic {
         }
 
         castable! {
-            $type: Self::TYPE_NAME,
+            $type: <Self as $crate::eval::Type>::TYPE_NAME,
             $($tts)*
             @this: Self => this.clone(),
         }
@@ -379,16 +405,62 @@ macro_rules! castable {
 
 primitive! { bool: "boolean", Bool }
 primitive! { i64: "integer", Int }
+primitive! { f64: "float", Float, Int(v) => v as f64 }
 primitive! { Length: "length", Length }
 primitive! { Angle: "angle", Angle }
 primitive! { Relative: "relative", Relative }
 primitive! { Linear: "linear", Linear, Length(v) => v.into(), Relative(v) => v.into() }
 primitive! { Fractional: "fractional", Fractional }
 primitive! { Color: "color", Color }
-primitive! { EcoString: "string", Str }
+primitive! { Str: "string", Str }
 primitive! { Array: "array", Array }
 primitive! { Dict: "dictionary", Dict }
 primitive! { Template: "template", Template }
 primitive! { Function: "function", Func }
-primitive! { Rc<FuncArgs>: "arguments", Args }
-primitive! { f64: "float", Float, Int(v) => v as f64 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[track_caller]
+    fn test(value: impl Into<Value>, exp: &str) {
+        assert_eq!(value.into().to_string(), exp);
+    }
+
+    #[test]
+    fn test_value_to_string() {
+        // Primitives.
+        test(Value::None, "none");
+        test(false, "false");
+        test(12i64, "12");
+        test(3.14, "3.14");
+        test(Length::pt(5.5), "5.5pt");
+        test(Angle::deg(90.0), "90deg");
+        test(Relative::one() / 2.0, "50%");
+        test(Relative::new(0.3) + Length::cm(2.0), "30% + 2cm");
+        test(Fractional::one() * 7.55, "7.55fr");
+        test(Color::Rgba(RgbaColor::new(1, 1, 1, 0xff)), "#010101");
+
+        // Collections.
+        test("hello", r#""hello""#);
+        test("\n", r#""\n""#);
+        test("\\", r#""\\""#);
+        test("\"", r#""\"""#);
+        test(array![], "()");
+        test(array![Value::None], "(none,)");
+        test(array![1, 2], "(1, 2)");
+        test(dict![], "(:)");
+        test(dict!["one" => 1], "(one: 1)");
+        test(dict!["two" => false, "one" => 1], "(one: 1, two: false)");
+
+        // Functions.
+        test(Function::new(None, |_, _| Ok(Value::None)), "<function>");
+        test(
+            Function::new(Some("nil".into()), |_, _| Ok(Value::None)),
+            "<function nil>",
+        );
+
+        // Dynamics.
+        test(Dynamic::new(1), "1");
+    }
+}
diff --git a/src/exec/mod.rs b/src/exec/mod.rs
index 373a32637..ac4c1fcac 100644
--- a/src/exec/mod.rs
+++ b/src/exec/mod.rs
@@ -11,7 +11,6 @@ use std::fmt::Write;
 use crate::eval::{ExprMap, Template, TemplateFunc, TemplateNode, TemplateTree, Value};
 use crate::geom::Gen;
 use crate::layout::{LayoutTree, StackChild, StackNode};
-use crate::pretty::pretty;
 use crate::syntax::*;
 use crate::util::EcoString;
 use crate::Context;
@@ -133,13 +132,13 @@ impl Exec for Value {
     fn exec(&self, ctx: &mut ExecContext) {
         match self {
             Value::None => {}
-            Value::Int(v) => ctx.push_text(pretty(v)),
-            Value::Float(v) => ctx.push_text(pretty(v)),
+            Value::Int(v) => ctx.push_text(v.to_string()),
+            Value::Float(v) => ctx.push_text(v.to_string()),
             Value::Str(v) => ctx.push_text(v),
             Value::Template(v) => v.exec(ctx),
             // For values which can't be shown "naturally", we print the
             // representation in monospace.
-            other => ctx.push_monospace_text(pretty(other)),
+            other => ctx.push_monospace_text(other.to_string()),
         }
     }
 }
diff --git a/src/layout/grid.rs b/src/layout/grid.rs
index bccdf3811..0a1895134 100644
--- a/src/layout/grid.rs
+++ b/src/layout/grid.rs
@@ -383,7 +383,7 @@ impl<'a> GridLayouter<'a> {
             let frames = self.layout_multi_row(ctx, first, &rest, y);
             let len = frames.len();
             for (i, frame) in frames.into_iter().enumerate() {
-                if i + 1 != len {
+                if i + 1 < len {
                     self.constraints.exact.set(self.main, Some(self.full));
                 }
                 self.push_row(ctx, frame);
diff --git a/src/layout/stack.rs b/src/layout/stack.rs
index ed053dd7e..7f0f2b9d1 100644
--- a/src/layout/stack.rs
+++ b/src/layout/stack.rs
@@ -111,7 +111,7 @@ impl<'a> StackLayouter<'a> {
                     let nodes = node.layout(ctx, &self.regions);
                     let len = nodes.len();
                     for (i, frame) in nodes.into_iter().enumerate() {
-                        if i + 1 != len {
+                        if i + 1 < len {
                             self.constraints.exact = self.full.to_spec().map(Some);
                         }
                         self.push_frame(frame.item, aligns);
diff --git a/src/lib.rs b/src/lib.rs
index 7447dad74..ce753f869 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -43,7 +43,6 @@ pub mod library;
 pub mod loading;
 pub mod paper;
 pub mod parse;
-pub mod pretty;
 pub mod source;
 pub mod syntax;
 pub mod util;
diff --git a/src/library/elements.rs b/src/library/elements.rs
index f0e36994b..1ad56a81a 100644
--- a/src/library/elements.rs
+++ b/src/library/elements.rs
@@ -10,8 +10,8 @@ use crate::layout::{
 };
 
 /// `image`: An image.
-pub fn image(ctx: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
-    let path = args.expect::<Spanned<EcoString>>("path to image file")?;
+pub fn image(ctx: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
+    let path = args.expect::<Spanned<Str>>("path to image file")?;
     let width = args.named("width")?;
     let height = args.named("height")?;
 
@@ -29,7 +29,7 @@ pub fn image(ctx: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
 }
 
 /// `rect`: A rectangle with optional content.
-pub fn rect(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn rect(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     let width = args.named("width")?;
     let height = args.named("height")?;
     let fill = args.named("fill")?;
@@ -38,7 +38,7 @@ pub fn rect(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
 }
 
 /// `square`: A square with optional content.
-pub fn square(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn square(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     let length = args.named::<Length>("length")?.map(Linear::from);
     let width = match length {
         Some(length) => Some(length),
@@ -80,7 +80,7 @@ fn rect_impl(
 }
 
 /// `ellipse`: An ellipse with optional content.
-pub fn ellipse(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn ellipse(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     let width = args.named("width")?;
     let height = args.named("height")?;
     let fill = args.named("fill")?;
@@ -89,7 +89,7 @@ pub fn ellipse(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
 }
 
 /// `circle`: A circle with optional content.
-pub fn circle(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn circle(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     let diameter = args.named("radius")?.map(|r: Length| 2.0 * Linear::from(r));
     let width = match diameter {
         None => args.named("width")?,
diff --git a/src/library/layout.rs b/src/library/layout.rs
index 53e3a450e..20673c4ab 100644
--- a/src/library/layout.rs
+++ b/src/library/layout.rs
@@ -3,8 +3,8 @@ use crate::layout::{FixedNode, GridNode, PadNode, StackChild, StackNode, TrackSi
 use crate::paper::{Paper, PaperClass};
 
 /// `page`: Configure pages.
-pub fn page(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
-    let paper = match args.eat::<Spanned<EcoString>>() {
+pub fn page(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
+    let paper = match args.eat::<Spanned<Str>>() {
         Some(name) => match Paper::from_name(&name.v) {
             None => bail!(name.span, "invalid paper name"),
             paper => paper,
@@ -74,21 +74,21 @@ pub fn page(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
 }
 
 /// `pagebreak`: Start a new page.
-pub fn pagebreak(_: &mut EvalContext, _: &mut FuncArgs) -> TypResult<Value> {
+pub fn pagebreak(_: &mut EvalContext, _: &mut Arguments) -> TypResult<Value> {
     Ok(Value::template(move |ctx| ctx.pagebreak(true, true)))
 }
 
 /// `h`: Horizontal spacing.
-pub fn h(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn h(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     spacing_impl(args, GenAxis::Cross)
 }
 
 /// `v`: Vertical spacing.
-pub fn v(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn v(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     spacing_impl(args, GenAxis::Main)
 }
 
-fn spacing_impl(args: &mut FuncArgs, axis: GenAxis) -> TypResult<Value> {
+fn spacing_impl(args: &mut Arguments, axis: GenAxis) -> TypResult<Value> {
     let spacing = args.expect::<Linear>("spacing")?;
     Ok(Value::template(move |ctx| {
         // TODO: Should this really always be font-size relative?
@@ -98,7 +98,7 @@ fn spacing_impl(args: &mut FuncArgs, axis: GenAxis) -> TypResult<Value> {
 }
 
 /// `align`: Configure the alignment along the layouting axes.
-pub fn align(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn align(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     let mut horizontal = args.named("horizontal")?;
     let mut vertical = args.named("vertical")?;
     let first = args.eat::<Align>();
@@ -132,7 +132,7 @@ pub fn align(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
 }
 
 /// `box`: Place content in a rectangular box.
-pub fn boxed(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn boxed(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     let width = args.named("width")?;
     let height = args.named("height")?;
     let body = args.eat().unwrap_or_default();
@@ -143,7 +143,7 @@ pub fn boxed(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
 }
 
 /// `block`: Place content in a block.
-pub fn block(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn block(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     let body = args.expect("body")?;
     Ok(Value::template(move |ctx| {
         let block = ctx.exec_template_stack(&body);
@@ -152,7 +152,7 @@ pub fn block(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
 }
 
 /// `pad`: Pad content at the sides.
-pub fn pad(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn pad(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     let all = args.eat();
     let left = args.named("left")?;
     let top = args.named("top")?;
@@ -174,7 +174,7 @@ pub fn pad(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
 }
 
 /// `stack`: Stack children along an axis.
-pub fn stack(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn stack(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     let dir = args.named("dir")?;
     let children: Vec<_> = args.all().collect();
 
@@ -200,7 +200,7 @@ pub fn stack(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
 }
 
 /// `grid`: Arrange children into a grid.
-pub fn grid(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn grid(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     let columns = args.named("columns")?.unwrap_or_default();
     let rows = args.named("rows")?.unwrap_or_default();
 
diff --git a/src/library/mod.rs b/src/library/mod.rs
index 3591e742c..f1134282c 100644
--- a/src/library/mod.rs
+++ b/src/library/mod.rs
@@ -18,12 +18,11 @@ use std::rc::Rc;
 
 use crate::color::{Color, RgbaColor};
 use crate::diag::TypResult;
-use crate::eval::{EvalContext, FuncArgs, Scope, Template, Type, Value};
+use crate::eval::{Arguments, EvalContext, Scope, Str, Template, Value};
 use crate::exec::Exec;
 use crate::font::{FontFamily, FontStretch, FontStyle, FontWeight, VerticalFontMetric};
 use crate::geom::*;
 use crate::syntax::Spanned;
-use crate::util::EcoString;
 
 /// Construct a scope containing all standard library definitions.
 pub fn new() -> Scope {
diff --git a/src/library/text.rs b/src/library/text.rs
index 55cabd15d..9ffb182af 100644
--- a/src/library/text.rs
+++ b/src/library/text.rs
@@ -4,7 +4,7 @@ use crate::layout::Paint;
 use super::*;
 
 /// `font`: Configure the font.
-pub fn font(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn font(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     let size = args.named::<Linear>("size")?.or_else(|| args.eat());
     let style = args.named("style")?;
     let weight = args.named("weight")?;
@@ -98,13 +98,13 @@ castable! {
         values
             .into_iter()
             .filter_map(|v| v.cast().ok())
-            .map(|string: EcoString| string.to_lowercase())
+            .map(|string: Str| string.to_lowercase())
             .collect()
     )),
 }
 
 /// `par`: Configure paragraphs.
-pub fn par(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn par(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     let par_spacing = args.named("spacing")?;
     let line_spacing = args.named("leading")?;
     let body = args.expect::<Template>("body")?;
@@ -126,8 +126,8 @@ pub fn par(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
 }
 
 /// `lang`: Configure the language.
-pub fn lang(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
-    let iso = args.eat::<EcoString>();
+pub fn lang(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
+    let iso = args.eat::<Str>();
     let dir = if let Some(dir) = args.named::<Spanned<Dir>>("dir")? {
         if dir.v.axis() == SpecAxis::Horizontal {
             Some(dir.v)
@@ -160,22 +160,22 @@ fn lang_dir(iso: &str) -> Dir {
 }
 
 /// `strike`: Enable striken-through text.
-pub fn strike(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn strike(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     line_impl(args, |font| &mut font.strikethrough)
 }
 
 /// `underline`: Enable underlined text.
-pub fn underline(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn underline(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     line_impl(args, |font| &mut font.underline)
 }
 
 /// `overline`: Add an overline above text.
-pub fn overline(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn overline(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     line_impl(args, |font| &mut font.overline)
 }
 
 fn line_impl(
-    args: &mut FuncArgs,
+    args: &mut Arguments,
     substate: fn(&mut FontState) -> &mut Option<Rc<LineState>>,
 ) -> TypResult<Value> {
     let stroke = args.named("stroke")?.or_else(|| args.eat());
diff --git a/src/library/utility.rs b/src/library/utility.rs
index 20d10830a..84f1d7ab4 100644
--- a/src/library/utility.rs
+++ b/src/library/utility.rs
@@ -2,37 +2,34 @@ use std::cmp::Ordering;
 use std::str::FromStr;
 
 use crate::color::{Color, RgbaColor};
-use crate::pretty::pretty;
 
 use super::*;
 
 /// `type`: The name of a value's type.
-pub fn type_(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
-    let value = args.expect::<Value>("value")?;
-    Ok(value.type_name().into())
+pub fn type_(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
+    Ok(args.expect::<Value>("value")?.type_name().into())
 }
 
 /// `repr`: The string representation of a value.
-pub fn repr(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
-    let value = args.expect::<Value>("value")?;
-    Ok(pretty(&value).into())
+pub fn repr(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
+    Ok(args.expect::<Value>("value")?.to_string().into())
 }
 
 /// `len`: The length of a string, an array or a dictionary.
-pub fn len(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn len(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     let Spanned { v, span } = args.expect("collection")?;
-    Ok(match v {
-        Value::Str(v) => Value::Int(v.len() as i64),
-        Value::Array(v) => Value::Int(v.len()),
-        Value::Dict(v) => Value::Int(v.len()),
+    Ok(Value::Int(match v {
+        Value::Str(v) => v.len(),
+        Value::Array(v) => v.len(),
+        Value::Dict(v) => v.len(),
         _ => bail!(span, "expected string, array or dictionary"),
-    })
+    }))
 }
 
 /// `rgb`: Create an RGB(A) color.
-pub fn rgb(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn rgb(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     Ok(Value::Color(Color::Rgba(
-        if let Some(string) = args.eat::<Spanned<EcoString>>() {
+        if let Some(string) = args.eat::<Spanned<Str>>() {
             match RgbaColor::from_str(&string.v) {
                 Ok(color) => color,
                 Err(_) => bail!(string.span, "invalid color"),
@@ -49,35 +46,32 @@ pub fn rgb(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
 }
 
 /// `min`: The minimum of a sequence of values.
-pub fn min(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn min(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     minmax(args, Ordering::Less)
 }
 
 /// `max`: The maximum of a sequence of values.
-pub fn max(_: &mut EvalContext, args: &mut FuncArgs) -> TypResult<Value> {
+pub fn max(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
     minmax(args, Ordering::Greater)
 }
 
 /// Find the minimum or maximum of a sequence of values.
-fn minmax(args: &mut FuncArgs, goal: Ordering) -> TypResult<Value> {
-    let span = args.span;
-
+fn minmax(args: &mut Arguments, goal: Ordering) -> TypResult<Value> {
     let mut extremum = args.expect::<Value>("value")?;
-    for value in args.all::<Value>() {
-        match value.partial_cmp(&extremum) {
+    for Spanned { v, span } in args.all::<Spanned<Value>>() {
+        match v.partial_cmp(&extremum) {
             Some(ordering) => {
                 if ordering == goal {
-                    extremum = value;
+                    extremum = v;
                 }
             }
             None => bail!(
                 span,
                 "cannot compare {} with {}",
                 extremum.type_name(),
-                value.type_name(),
+                v.type_name(),
             ),
         }
     }
-
     Ok(extremum)
 }
diff --git a/src/parse/resolve.rs b/src/parse/resolve.rs
index 7ceac1289..80e3bbc00 100644
--- a/src/parse/resolve.rs
+++ b/src/parse/resolve.rs
@@ -29,12 +29,12 @@ pub fn resolve_string(string: &str) -> EcoString {
                     out.push(c);
                 } else {
                     // TODO: Feedback that unicode escape sequence is wrong.
-                    out += s.eaten_from(start);
+                    out.push_str(s.eaten_from(start));
                 }
             }
 
             // TODO: Feedback about invalid escape sequence.
-            _ => out += s.eaten_from(start),
+            _ => out.push_str(s.eaten_from(start)),
         }
     }
 
@@ -138,7 +138,7 @@ mod tests {
     fn test_resolve_strings() {
         #[track_caller]
         fn test(string: &str, expected: &str) {
-            assert_eq!(resolve_string(string), expected.to_string());
+            assert_eq!(resolve_string(string), expected);
         }
 
         test(r#"hello world"#,  "hello world");
diff --git a/src/parse/tokens.rs b/src/parse/tokens.rs
index acd939e83..684e340e2 100644
--- a/src/parse/tokens.rs
+++ b/src/parse/tokens.rs
@@ -606,20 +606,20 @@ mod tests {
         }};
         (@$mode:ident: $src:expr => $($token:expr),*) => {{
             let src = $src;
-            let exp = vec![$($token),*];
             let found = Tokens::new(&src, $mode).collect::<Vec<_>>();
-            check(&src, exp, found);
+            let expected = vec![$($token),*];
+            check(&src, found, expected);
         }};
     }
 
     #[track_caller]
-    fn check<T>(src: &str, exp: T, found: T)
+    fn check<T>(src: &str, found: T, expected: T)
     where
         T: Debug + PartialEq,
     {
-        if exp != found {
+        if found != expected {
             println!("source:   {:?}", src);
-            println!("expected: {:#?}", exp);
+            println!("expected: {:#?}", expected);
             println!("found:    {:#?}", found);
             panic!("test failed");
         }
diff --git a/src/syntax/ident.rs b/src/syntax/ident.rs
index 462361a5b..2a7df8e11 100644
--- a/src/syntax/ident.rs
+++ b/src/syntax/ident.rs
@@ -23,14 +23,11 @@ pub struct Ident {
 impl Ident {
     /// Create a new identifier from a string checking that it is a valid.
     pub fn new(
-        string: impl AsRef<str> + Into<String>,
+        string: impl AsRef<str> + Into<EcoString>,
         span: impl Into<Span>,
     ) -> Option<Self> {
         if is_ident(string.as_ref()) {
-            Some(Self {
-                span: span.into(),
-                string: EcoString::from_str(string),
-            })
+            Some(Self { span: span.into(), string: string.into() })
         } else {
             None
         }
diff --git a/src/syntax/mod.rs b/src/syntax/mod.rs
index 9a4ca708a..f07e3554a 100644
--- a/src/syntax/mod.rs
+++ b/src/syntax/mod.rs
@@ -3,6 +3,7 @@
 mod expr;
 mod ident;
 mod node;
+mod pretty;
 mod span;
 mod token;
 pub mod visit;
@@ -10,6 +11,7 @@ pub mod visit;
 pub use expr::*;
 pub use ident::*;
 pub use node::*;
+pub use pretty::*;
 pub use span::*;
 pub use token::*;
 
diff --git a/src/pretty.rs b/src/syntax/pretty.rs
similarity index 74%
rename from src/pretty.rs
rename to src/syntax/pretty.rs
index 573dc6e9c..40ebf7584 100644
--- a/src/pretty.rs
+++ b/src/syntax/pretty.rs
@@ -2,10 +2,7 @@
 
 use std::fmt::{self, Arguments, Write};
 
-use crate::color::{Color, RgbaColor};
-use crate::eval::*;
-use crate::geom::{Angle, Fractional, Length, Linear, Relative};
-use crate::syntax::*;
+use super::*;
 
 /// Pretty print an item and return the resulting string.
 pub fn pretty<T>(item: &T) -> String
@@ -23,7 +20,7 @@ pub trait Pretty {
     fn pretty(&self, p: &mut Printer);
 }
 
-/// A buffer into which items are printed.
+/// A buffer into which items can be pretty printed.
 pub struct Printer {
     buf: String,
 }
@@ -223,14 +220,14 @@ impl Pretty for Lit {
         match self {
             Self::None(_) => p.push_str("none"),
             Self::Auto(_) => p.push_str("auto"),
-            Self::Bool(_, v) => v.pretty(p),
-            Self::Int(_, v) => v.pretty(p),
-            Self::Float(_, v) => v.pretty(p),
+            Self::Bool(_, v) => write!(p, "{}", v).unwrap(),
+            Self::Int(_, v) => write!(p, "{}", v).unwrap(),
+            Self::Float(_, v) => write!(p, "{}", v).unwrap(),
             Self::Length(_, v, u) => write!(p, "{}{}", v, u).unwrap(),
             Self::Angle(_, v, u) => write!(p, "{}{}", v, u).unwrap(),
             Self::Percent(_, v) => write!(p, "{}%", v).unwrap(),
             Self::Fractional(_, v) => write!(p, "{}fr", v).unwrap(),
-            Self::Str(_, v) => v.pretty(p),
+            Self::Str(_, v) => write!(p, "{:?}", v).unwrap(),
         }
     }
 }
@@ -493,134 +490,6 @@ impl Pretty for Ident {
     }
 }
 
-impl Pretty for Value {
-    fn pretty(&self, p: &mut Printer) {
-        match self {
-            Self::None => p.push_str("none"),
-            Self::Auto => p.push_str("auto"),
-            Self::Bool(v) => v.pretty(p),
-            Self::Int(v) => v.pretty(p),
-            Self::Float(v) => v.pretty(p),
-            Self::Length(v) => v.pretty(p),
-            Self::Angle(v) => v.pretty(p),
-            Self::Relative(v) => v.pretty(p),
-            Self::Linear(v) => v.pretty(p),
-            Self::Fractional(v) => v.pretty(p),
-            Self::Color(v) => v.pretty(p),
-            Self::Str(v) => v.pretty(p),
-            Self::Array(v) => v.pretty(p),
-            Self::Dict(v) => v.pretty(p),
-            Self::Template(v) => v.pretty(p),
-            Self::Func(v) => v.pretty(p),
-            Self::Args(v) => v.pretty(p),
-            Self::Dyn(v) => v.pretty(p),
-        }
-    }
-}
-
-impl Pretty for Array {
-    fn pretty(&self, p: &mut Printer) {
-        p.push('(');
-        p.join(self, ", ", |item, p| item.pretty(p));
-        if self.len() == 1 {
-            p.push(',');
-        }
-        p.push(')');
-    }
-}
-
-impl Pretty for Dict {
-    fn pretty(&self, p: &mut Printer) {
-        p.push('(');
-        if self.is_empty() {
-            p.push(':');
-        } else {
-            p.join(self, ", ", |(key, value), p| {
-                p.push_str(key);
-                p.push_str(": ");
-                value.pretty(p);
-            });
-        }
-        p.push(')');
-    }
-}
-
-impl Pretty for Template {
-    fn pretty(&self, p: &mut Printer) {
-        p.push_str("<template>");
-    }
-}
-
-impl Pretty for Function {
-    fn pretty(&self, p: &mut Printer) {
-        p.push_str("<function");
-        if let Some(name) = self.name() {
-            p.push(' ');
-            p.push_str(name);
-        }
-        p.push('>');
-    }
-}
-
-impl Pretty for FuncArgs {
-    fn pretty(&self, p: &mut Printer) {
-        p.push('(');
-        p.join(&self.items, ", ", |item, p| item.pretty(p));
-        p.push(')');
-    }
-}
-
-impl Pretty for FuncArg {
-    fn pretty(&self, p: &mut Printer) {
-        if let Some(name) = &self.name {
-            p.push_str(&name);
-            p.push_str(": ");
-        }
-        self.value.v.pretty(p);
-    }
-}
-
-impl Pretty for str {
-    fn pretty(&self, p: &mut Printer) {
-        p.push('"');
-        for c in self.chars() {
-            match c {
-                '\\' => p.push_str(r"\\"),
-                '"' => p.push_str(r#"\""#),
-                '\n' => p.push_str(r"\n"),
-                '\r' => p.push_str(r"\r"),
-                '\t' => p.push_str(r"\t"),
-                _ => p.push(c),
-            }
-        }
-        p.push('"');
-    }
-}
-
-macro_rules! pretty_display {
-    ($($type:ty),* $(,)?) => {
-        $(impl Pretty for $type {
-            fn pretty(&self, p: &mut Printer) {
-                write!(p, "{}", self).unwrap();
-            }
-        })*
-    };
-}
-
-pretty_display! {
-    i64,
-    f64,
-    bool,
-    Length,
-    Angle,
-    Relative,
-    Linear,
-    Fractional,
-    RgbaColor,
-    Color,
-    Dynamic,
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -633,23 +502,18 @@ mod tests {
     }
 
     #[track_caller]
-    fn test_parse(src: &str, exp: &str) {
+    fn test_parse(src: &str, expected: &str) {
         let source = SourceFile::detached(src);
         let ast = parse(&source).unwrap();
         let found = pretty(&ast);
-        if exp != found {
+        if found != expected {
             println!("tree:     {:#?}", ast);
-            println!("expected: {}", exp);
+            println!("expected: {}", expected);
             println!("found:    {}", found);
             panic!("test failed");
         }
     }
 
-    #[track_caller]
-    fn test_value(value: impl Into<Value>, exp: &str) {
-        assert_eq!(pretty(&value.into()), exp);
-    }
-
     #[test]
     fn test_pretty_print_node() {
         // Basic text and markup.
@@ -746,41 +610,4 @@ mod tests {
         roundtrip("#import * from \"file.typ\"");
         roundtrip("#include \"chapter1.typ\"");
     }
-
-    #[test]
-    fn test_pretty_print_value() {
-        // Primitives.
-        test_value(Value::None, "none");
-        test_value(false, "false");
-        test_value(12i64, "12");
-        test_value(3.14, "3.14");
-        test_value(Length::pt(5.5), "5.5pt");
-        test_value(Angle::deg(90.0), "90deg");
-        test_value(Relative::one() / 2.0, "50%");
-        test_value(Relative::new(0.3) + Length::cm(2.0), "30% + 2cm");
-        test_value(Fractional::one() * 7.55, "7.55fr");
-        test_value(Color::Rgba(RgbaColor::new(1, 1, 1, 0xff)), "#010101");
-
-        // Collections.
-        test_value("hello", r#""hello""#);
-        test_value("\n", r#""\n""#);
-        test_value("\\", r#""\\""#);
-        test_value("\"", r#""\"""#);
-        test_value(array![], "()");
-        test_value(array![Value::None], "(none,)");
-        test_value(array![1, 2], "(1, 2)");
-        test_value(dict![], "(:)");
-        test_value(dict!["one" => 1], "(one: 1)");
-        test_value(dict!["two" => false, "one" => 1], "(one: 1, two: false)");
-
-        // Functions.
-        test_value(Function::new(None, |_, _| Ok(Value::None)), "<function>");
-        test_value(
-            Function::new(Some("nil".into()), |_, _| Ok(Value::None)),
-            "<function nil>",
-        );
-
-        // Dynamics.
-        test_value(Dynamic::new(1), "1");
-    }
 }
diff --git a/src/syntax/span.rs b/src/syntax/span.rs
index cad9c5d53..e4a4fd328 100644
--- a/src/syntax/span.rs
+++ b/src/syntax/span.rs
@@ -142,18 +142,6 @@ impl Pos {
     }
 }
 
-impl From<u32> for Pos {
-    fn from(index: u32) -> Self {
-        Self(index)
-    }
-}
-
-impl From<usize> for Pos {
-    fn from(index: usize) -> Self {
-        Self(index as u32)
-    }
-}
-
 impl Debug for Pos {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         Debug::fmt(&self.0, f)
@@ -171,6 +159,18 @@ where
     }
 }
 
+impl From<u32> for Pos {
+    fn from(index: u32) -> Self {
+        Self(index)
+    }
+}
+
+impl From<usize> for Pos {
+    fn from(index: usize) -> Self {
+        Self(index as u32)
+    }
+}
+
 /// Convert a position or range into a span.
 pub trait IntoSpan {
     /// Convert into a span by providing the source id.
diff --git a/src/util/eco.rs b/src/util/eco.rs
index 08c2117d1..207f1753b 100644
--- a/src/util/eco.rs
+++ b/src/util/eco.rs
@@ -1,14 +1,11 @@
 use std::borrow::Borrow;
 use std::cmp::Ordering;
-use std::convert::TryFrom;
 use std::fmt::{self, Debug, Display, Formatter, Write};
 use std::hash::{Hash, Hasher};
-use std::ops::{Add, AddAssign, Deref};
+use std::ops::Deref;
 use std::rc::Rc;
 
-use crate::diag::StrResult;
-
-/// An economical string with inline storage and clone-on-write value semantics.
+/// An economical string with inline storage and clone-on-write semantics.
 #[derive(Clone)]
 pub struct EcoString(Repr);
 
@@ -144,75 +141,25 @@ impl EcoString {
     }
 
     /// Repeat this string `n` times.
-    pub fn repeat(&self, n: i64) -> StrResult<Self> {
-        let (n, new) = usize::try_from(n)
-            .ok()
-            .and_then(|n| self.len().checked_mul(n).map(|new| (n, new)))
-            .ok_or_else(|| format!("cannot repeat this string {} times", n))?;
+    pub fn repeat(&self, n: usize) -> Self {
+        if n == 0 {
+            return Self::new();
+        }
 
         if let Repr::Small { buf, len } = &self.0 {
             let prev = usize::from(*len);
+            let new = prev.saturating_mul(n);
             if new <= LIMIT {
                 let src = &buf[.. prev];
                 let mut buf = [0; LIMIT];
                 for i in 0 .. n {
                     buf[prev * i .. prev * (i + 1)].copy_from_slice(src);
                 }
-                return Ok(Self(Repr::Small { buf, len: new as u8 }));
+                return Self(Repr::Small { buf, len: new as u8 });
             }
         }
 
-        Ok(self.as_str().repeat(n).into())
-    }
-}
-
-impl From<&Self> for EcoString {
-    fn from(s: &Self) -> Self {
-        s.clone()
-    }
-}
-
-impl From<char> for EcoString {
-    fn from(c: char) -> Self {
-        let mut buf = [0; LIMIT];
-        let len = c.encode_utf8(&mut buf).len();
-        Self(Repr::Small { buf, len: len as u8 })
-    }
-}
-
-impl From<&str> for EcoString {
-    fn from(s: &str) -> Self {
-        Self::from_str(s)
-    }
-}
-
-impl From<String> for EcoString {
-    fn from(s: String) -> Self {
-        Self::from_str(s)
-    }
-}
-
-impl From<&String> for EcoString {
-    fn from(s: &String) -> Self {
-        Self::from_str(s)
-    }
-}
-
-impl From<EcoString> for String {
-    fn from(s: EcoString) -> Self {
-        match s.0 {
-            Repr::Small { .. } => s.as_str().to_owned(),
-            Repr::Large(rc) => match Rc::try_unwrap(rc) {
-                Ok(string) => string,
-                Err(rc) => (*rc).clone(),
-            },
-        }
-    }
-}
-
-impl From<&EcoString> for String {
-    fn from(s: &EcoString) -> Self {
-        s.as_str().to_owned()
+        self.as_str().repeat(n).into()
     }
 }
 
@@ -236,18 +183,6 @@ impl Deref for EcoString {
     }
 }
 
-impl AsRef<str> for EcoString {
-    fn as_ref(&self) -> &str {
-        self
-    }
-}
-
-impl Borrow<str> for EcoString {
-    fn borrow(&self) -> &str {
-        self
-    }
-}
-
 impl Default for EcoString {
     fn default() -> Self {
         Self::new()
@@ -286,12 +221,6 @@ impl PartialEq<&str> for EcoString {
     }
 }
 
-impl PartialEq<String> for EcoString {
-    fn eq(&self, other: &String) -> bool {
-        self.as_str().eq(other.as_str())
-    }
-}
-
 impl Ord for EcoString {
     fn cmp(&self, other: &Self) -> Ordering {
         self.as_str().cmp(other.as_str())
@@ -304,35 +233,6 @@ impl PartialOrd for EcoString {
     }
 }
 
-impl Add for EcoString {
-    type Output = Self;
-
-    fn add(self, rhs: Self) -> Self::Output {
-        self + rhs.as_str()
-    }
-}
-
-impl AddAssign for EcoString {
-    fn add_assign(&mut self, rhs: EcoString) {
-        self.push_str(&rhs);
-    }
-}
-
-impl Add<&str> for EcoString {
-    type Output = Self;
-
-    fn add(mut self, rhs: &str) -> Self::Output {
-        self.push_str(rhs);
-        self
-    }
-}
-
-impl AddAssign<&str> for EcoString {
-    fn add_assign(&mut self, rhs: &str) {
-        self.push_str(rhs);
-    }
-}
-
 impl Hash for EcoString {
     fn hash<H: Hasher>(&self, state: &mut H) {
         self.as_str().hash(state);
@@ -351,6 +251,62 @@ impl Write for EcoString {
     }
 }
 
+impl AsRef<str> for EcoString {
+    fn as_ref(&self) -> &str {
+        self
+    }
+}
+
+impl Borrow<str> for EcoString {
+    fn borrow(&self) -> &str {
+        self
+    }
+}
+
+impl From<&Self> for EcoString {
+    fn from(s: &Self) -> Self {
+        s.clone()
+    }
+}
+
+impl From<char> for EcoString {
+    fn from(c: char) -> Self {
+        let mut buf = [0; LIMIT];
+        let len = c.encode_utf8(&mut buf).len();
+        Self(Repr::Small { buf, len: len as u8 })
+    }
+}
+
+impl From<&str> for EcoString {
+    fn from(s: &str) -> Self {
+        Self::from_str(s)
+    }
+}
+
+impl From<String> for EcoString {
+    fn from(s: String) -> Self {
+        Self::from_str(s)
+    }
+}
+
+impl From<EcoString> for String {
+    fn from(s: EcoString) -> Self {
+        match s.0 {
+            Repr::Small { .. } => s.as_str().to_owned(),
+            Repr::Large(rc) => match Rc::try_unwrap(rc) {
+                Ok(string) => string,
+                Err(rc) => (*rc).clone(),
+            },
+        }
+    }
+}
+
+impl From<&EcoString> for String {
+    fn from(s: &EcoString) -> Self {
+        s.as_str().to_owned()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -436,17 +392,13 @@ mod tests {
     #[test]
     fn test_str_repeat() {
         // Test with empty string.
-        assert_eq!(EcoString::new().repeat(0).unwrap(), "");
-        assert_eq!(EcoString::new().repeat(100).unwrap(), "");
+        assert_eq!(EcoString::new().repeat(0), "");
+        assert_eq!(EcoString::new().repeat(100), "");
 
         // Test non-spilling and spilling case.
         let v = EcoString::from("abc");
-        assert_eq!(v.repeat(0).unwrap(), "");
-        assert_eq!(v.repeat(3).unwrap(), "abcabcabc");
-        assert_eq!(v.repeat(5).unwrap(), "abcabcabcabcabc");
-        assert_eq!(
-            v.repeat(-1).unwrap_err(),
-            "cannot repeat this string -1 times",
-        );
+        assert_eq!(v.repeat(0), "");
+        assert_eq!(v.repeat(3), "abcabcabc");
+        assert_eq!(v.repeat(5), "abcabcabcabcabc");
     }
 }
diff --git a/tests/typ/utility/math.typ b/tests/typ/utility/math.typ
index 3718866be..05c3639f5 100644
--- a/tests/typ/utility/math.typ
+++ b/tests/typ/utility/math.typ
@@ -13,5 +13,5 @@
 #min()
 
 ---
-// Error: 10-19 cannot compare integer with string
+// Error: 14-18 cannot compare integer with string
 #test(min(1, "hi"), error)