Remove index syntax in favor of accessor methods

23 files changed, 396 insertions, 236 deletions

diff --git a/src/model/args.rs b/src/model/args.rs
index fe5f8254..4aaaded4 100644
--- a/src/model/args.rs
+++ b/src/model/args.rs
@@ -165,36 +165,6 @@ impl Args {
             .filter_map(|item| item.name.clone().map(|name| (name, item.value.v.clone())))
             .collect()
     }
-
-    /// Reinterpret these arguments as actually being an array index.
-    pub fn into_index(self) -> SourceResult<i64> {
-        self.into_castable("index")
-    }
-
-    /// Reinterpret these arguments as actually being a dictionary key.
-    pub fn into_key(self) -> SourceResult<Str> {
-        self.into_castable("key")
-    }
-
-    /// Reinterpret these arguments as actually being a single castable thing.
-    fn into_castable<T: Cast>(self, what: &str) -> SourceResult<T> {
-        let mut iter = self.items.into_iter();
-        let value = match iter.next() {
-            Some(Arg { name: None, value, .. }) => value.v.cast().at(value.span)?,
-            None => {
-                bail!(self.span, "missing {}", what);
-            }
-            Some(Arg { name: Some(_), span, .. }) => {
-                bail!(span, "named pair is not allowed here");
-            }
-        };
-
-        if let Some(arg) = iter.next() {
-            bail!(arg.span, "only one {} is allowed", what);
-        }
-
-        Ok(value)
-    }
 }
 
 impl Debug for Args {
diff --git a/src/model/array.rs b/src/model/array.rs
index 02607547..fb740a13 100644
--- a/src/model/array.rs
+++ b/src/model/array.rs
@@ -4,7 +4,7 @@ use std::ops::{Add, AddAssign};
 use std::sync::Arc;
 
 use super::{ops, Args, Func, Value, Vm};
-use crate::diag::{At, SourceResult, StrResult};
+use crate::diag::{bail, At, SourceResult, StrResult};
 use crate::syntax::Spanned;
 use crate::util::{format_eco, ArcExt, EcoString};
 
@@ -45,24 +45,34 @@ impl Array {
     }
 
     /// The first value in the array.
-    pub fn first(&self) -> Option<&Value> {
-        self.0.first()
+    pub fn first(&self) -> StrResult<&Value> {
+        self.0.first().ok_or_else(array_is_empty)
+    }
+
+    /// Mutably borrow the first value in the array.
+    pub fn first_mut(&mut self) -> StrResult<&mut Value> {
+        Arc::make_mut(&mut self.0).first_mut().ok_or_else(array_is_empty)
     }
 
     /// The last value in the array.
-    pub fn last(&self) -> Option<&Value> {
-        self.0.last()
+    pub fn last(&self) -> StrResult<&Value> {
+        self.0.last().ok_or_else(array_is_empty)
+    }
+
+    /// Mutably borrow the last value in the array.
+    pub fn last_mut(&mut self) -> StrResult<&mut Value> {
+        Arc::make_mut(&mut self.0).last_mut().ok_or_else(array_is_empty)
     }
 
     /// Borrow the value at the given index.
-    pub fn get(&self, index: i64) -> StrResult<&Value> {
+    pub fn at(&self, index: i64) -> StrResult<&Value> {
         self.locate(index)
             .and_then(|i| self.0.get(i))
             .ok_or_else(|| out_of_bounds(index, self.len()))
     }
 
     /// Mutably borrow the value at the given index.
-    pub fn get_mut(&mut self, index: i64) -> StrResult<&mut Value> {
+    pub fn at_mut(&mut self, index: i64) -> StrResult<&mut Value> {
         let len = self.len();
         self.locate(index)
             .and_then(move |i| Arc::make_mut(&mut self.0).get_mut(i))
@@ -128,6 +138,9 @@ impl Array {
 
     /// Return the first matching element.
     pub fn find(&self, vm: &Vm, f: Spanned<Func>) -> SourceResult<Option<Value>> {
+        if f.v.argc().map_or(false, |count| count != 1) {
+            bail!(f.span, "function must have exactly one parameter");
+        }
         for item in self.iter() {
             let args = Args::new(f.span, [item.clone()]);
             if f.v.call(vm, args)?.cast::<bool>().at(f.span)? {
@@ -140,6 +153,9 @@ impl Array {
 
     /// Return the index of the first matching element.
     pub fn position(&self, vm: &Vm, f: Spanned<Func>) -> SourceResult<Option<i64>> {
+        if f.v.argc().map_or(false, |count| count != 1) {
+            bail!(f.span, "function must have exactly one parameter");
+        }
         for (i, item) in self.iter().enumerate() {
             let args = Args::new(f.span, [item.clone()]);
             if f.v.call(vm, args)?.cast::<bool>().at(f.span)? {
@@ -153,6 +169,9 @@ impl Array {
     /// Return a new array with only those elements for which the function
     /// returns true.
     pub fn filter(&self, vm: &Vm, f: Spanned<Func>) -> SourceResult<Self> {
+        if f.v.argc().map_or(false, |count| count != 1) {
+            bail!(f.span, "function must have exactly one parameter");
+        }
         let mut kept = vec![];
         for item in self.iter() {
             let args = Args::new(f.span, [item.clone()]);
@@ -165,6 +184,9 @@ impl Array {
 
     /// Transform each item in the array with a function.
     pub fn map(&self, vm: &Vm, f: Spanned<Func>) -> SourceResult<Self> {
+        if f.v.argc().map_or(false, |count| count < 1 || count > 2) {
+            bail!(f.span, "function must have one or two parameters");
+        }
         let enumerate = f.v.argc() == Some(2);
         self.iter()
             .enumerate()
@@ -179,8 +201,24 @@ impl Array {
             .collect()
     }
 
+    /// Fold all of the array's elements into one with a function.
+    pub fn fold(&self, vm: &Vm, init: Value, f: Spanned<Func>) -> SourceResult<Value> {
+        if f.v.argc().map_or(false, |count| count != 2) {
+            bail!(f.span, "function must have exactly two parameters");
+        }
+        let mut acc = init;
+        for item in self.iter() {
+            let args = Args::new(f.span, [acc, item.clone()]);
+            acc = f.v.call(vm, args)?;
+        }
+        Ok(acc)
+    }
+
     /// Whether any element matches.
     pub fn any(&self, vm: &Vm, f: Spanned<Func>) -> SourceResult<bool> {
+        if f.v.argc().map_or(false, |count| count != 1) {
+            bail!(f.span, "function must have exactly one parameter");
+        }
         for item in self.iter() {
             let args = Args::new(f.span, [item.clone()]);
             if f.v.call(vm, args)?.cast::<bool>().at(f.span)? {
@@ -193,6 +231,9 @@ impl Array {
 
     /// Whether all elements match.
     pub fn all(&self, vm: &Vm, f: Spanned<Func>) -> SourceResult<bool> {
+        if f.v.argc().map_or(false, |count| count != 1) {
+            bail!(f.span, "function must have exactly one parameter");
+        }
         for item in self.iter() {
             let args = Args::new(f.span, [item.clone()]);
             if !f.v.call(vm, args)?.cast::<bool>().at(f.span)? {
diff --git a/src/model/dict.rs b/src/model/dict.rs
index e3c5454e..83c16824 100644
--- a/src/model/dict.rs
+++ b/src/model/dict.rs
@@ -4,7 +4,7 @@ use std::ops::{Add, AddAssign};
 use std::sync::Arc;
 
 use super::{Args, Array, Func, Str, Value, Vm};
-use crate::diag::{SourceResult, StrResult};
+use crate::diag::{bail, SourceResult, StrResult};
 use crate::syntax::is_ident;
 use crate::syntax::Spanned;
 use crate::util::{format_eco, ArcExt, EcoString};
@@ -50,7 +50,7 @@ impl Dict {
     }
 
     /// Borrow the value the given `key` maps to.
-    pub fn get(&self, key: &str) -> StrResult<&Value> {
+    pub fn at(&self, key: &str) -> StrResult<&Value> {
         self.0.get(key).ok_or_else(|| missing_key(key))
     }
 
@@ -58,7 +58,7 @@ impl Dict {
     ///
     /// This inserts the key with [`None`](Value::None) as the value if not
     /// present so far.
-    pub fn get_mut(&mut self, key: Str) -> &mut Value {
+    pub fn at_mut(&mut self, key: Str) -> &mut Value {
         Arc::make_mut(&mut self.0).entry(key).or_default()
     }
 
@@ -108,6 +108,9 @@ impl Dict {
 
     /// Transform each pair in the dictionary with a function.
     pub fn map(&self, vm: &Vm, f: Spanned<Func>) -> SourceResult<Array> {
+        if f.v.argc().map_or(false, |count| count != 1) {
+            bail!(f.span, "function must have exactly two parameters");
+        }
         self.iter()
             .map(|(key, value)| {
                 let args = Args::new(f.span, [Value::Str(key.clone()), value.clone()]);
diff --git a/src/model/eval.rs b/src/model/eval.rs
index 54007e76..ab89f9c2 100644
--- a/src/model/eval.rs
+++ b/src/model/eval.rs
@@ -780,7 +780,7 @@ impl Eval for ast::FieldAccess {
         let field = self.field().take();
 
         Ok(match object {
-            Value::Dict(dict) => dict.get(&field).at(span)?.clone(),
+            Value::Dict(dict) => dict.at(&field).at(span)?.clone(),
             Value::Content(content) => content
                 .field(&field)
                 .ok_or_else(|| format!("unknown field {field:?}"))
@@ -798,22 +798,11 @@ impl Eval for ast::FuncCall {
             bail!(self.span(), "maximum function call depth exceeded");
         }
 
-        let callee = self.callee().eval(vm)?;
+        let callee = self.callee();
+        let callee = callee.eval(vm)?.cast::<Func>().at(callee.span())?;
         let args = self.args().eval(vm)?;
-
-        Ok(match callee {
-            Value::Array(array) => array.get(args.into_index()?).at(self.span())?.clone(),
-            Value::Dict(dict) => dict.get(&args.into_key()?).at(self.span())?.clone(),
-            Value::Func(func) => {
-                let point = || Tracepoint::Call(func.name().map(Into::into));
-                func.call(vm, args).trace(vm.world, point, self.span())?
-            }
-            v => bail!(
-                self.callee().span(),
-                "expected callable or collection, found {}",
-                v.type_name(),
-            ),
-        })
+        let point = || Tracepoint::Call(callee.name().map(Into::into));
+        callee.call(vm, args).trace(vm.world, point, self.span())
     }
 }
 
@@ -1246,9 +1235,13 @@ impl Access for ast::Expr {
     fn access<'a>(&self, vm: &'a mut Vm) -> SourceResult<&'a mut Value> {
         match self {
             Self::Ident(v) => v.access(vm),
+            Self::Parenthesized(v) => v.access(vm),
             Self::FieldAccess(v) => v.access(vm),
-            Self::FuncCall(v) => v.access(vm),
-            _ => bail!(self.span(), "cannot mutate a temporary value"),
+            Self::MethodCall(v) => v.access(vm),
+            _ => {
+                let _ = self.eval(vm)?;
+                bail!(self.span(), "cannot mutate a temporary value");
+            }
         }
     }
 }
@@ -1259,10 +1252,16 @@ impl Access for ast::Ident {
     }
 }
 
+impl Access for ast::Parenthesized {
+    fn access<'a>(&self, vm: &'a mut Vm) -> SourceResult<&'a mut Value> {
+        self.expr().access(vm)
+    }
+}
+
 impl Access for ast::FieldAccess {
     fn access<'a>(&self, vm: &'a mut Vm) -> SourceResult<&'a mut Value> {
         Ok(match self.target().access(vm)? {
-            Value::Dict(dict) => dict.get_mut(self.field().take().into()),
+            Value::Dict(dict) => dict.at_mut(self.field().take().into()),
             v => bail!(
                 self.target().span(),
                 "expected dictionary, found {}",
@@ -1272,17 +1271,17 @@ impl Access for ast::FieldAccess {
     }
 }
 
-impl Access for ast::FuncCall {
+impl Access for ast::MethodCall {
     fn access<'a>(&self, vm: &'a mut Vm) -> SourceResult<&'a mut Value> {
+        let span = self.span();
+        let method = self.method();
         let args = self.args().eval(vm)?;
-        Ok(match self.callee().access(vm)? {
-            Value::Array(array) => array.get_mut(args.into_index()?).at(self.span())?,
-            Value::Dict(dict) => dict.get_mut(args.into_key()?),
-            v => bail!(
-                self.callee().span(),
-                "expected collection, found {}",
-                v.type_name(),
-            ),
-        })
+        if methods::is_accessor(&method) {
+            let value = self.target().access(vm)?;
+            methods::call_access(value, &method, args, span)
+        } else {
+            let _ = self.eval(vm)?;
+            bail!(span, "cannot mutate a temporary value");
+        }
     }
 }
diff --git a/src/model/methods.rs b/src/model/methods.rs
index dac36be2..8155685c 100644
--- a/src/model/methods.rs
+++ b/src/model/methods.rs
@@ -1,6 +1,6 @@
 //! Methods on values.
 
-use super::{Args, Value, Vm};
+use super::{Args, Str, Value, Vm};
 use crate::diag::{At, SourceResult};
 use crate::syntax::Span;
 use crate::util::EcoString;
@@ -26,6 +26,9 @@ pub fn call(
 
         Value::Str(string) => match method {
             "len" => Value::Int(string.len() as i64),
+            "first" => Value::Str(string.first().at(span)?),
+            "last" => Value::Str(string.last().at(span)?),
+            "at" => Value::Str(string.at(args.expect("index")?).at(span)?),
             "slice" => {
                 let start = args.expect("start")?;
                 let mut end = args.eat()?;
@@ -65,8 +68,9 @@ pub fn call(
 
         Value::Array(array) => match method {
             "len" => Value::Int(array.len()),
-            "first" => array.first().cloned().unwrap_or(Value::None),
-            "last" => array.last().cloned().unwrap_or(Value::None),
+            "first" => array.first().at(span)?.clone(),
+            "last" => array.last().at(span)?.clone(),
+            "at" => array.at(args.expect("index")?).at(span)?.clone(),
             "slice" => {
                 let start = args.expect("start")?;
                 let mut end = args.eat()?;
@@ -82,6 +86,9 @@ pub fn call(
                 .map_or(Value::None, Value::Int),
             "filter" => Value::Array(array.filter(vm, args.expect("function")?)?),
             "map" => Value::Array(array.map(vm, args.expect("function")?)?),
+            "fold" => {
+                array.fold(vm, args.expect("initial value")?, args.expect("function")?)?
+            }
             "any" => Value::Bool(array.any(vm, args.expect("function")?)?),
             "all" => Value::Bool(array.all(vm, args.expect("function")?)?),
             "flatten" => Value::Array(array.flatten()),
@@ -97,6 +104,7 @@ pub fn call(
 
         Value::Dict(dict) => match method {
             "len" => Value::Int(dict.len()),
+            "at" => dict.at(&args.expect::<Str>("key")?).cloned().at(span)?,
             "keys" => Value::Array(dict.keys()),
             "values" => Value::Array(dict.values()),
             "pairs" => Value::Array(dict.map(vm, args.expect("function")?)?),
@@ -158,11 +166,44 @@ pub fn call_mut(
     Ok(output)
 }
 
+/// Call an accessor method on a value.
+pub fn call_access<'a>(
+    value: &'a mut Value,
+    method: &str,
+    mut args: Args,
+    span: Span,
+) -> SourceResult<&'a mut Value> {
+    let name = value.type_name();
+    let missing = || Err(missing_method(name, method)).at(span);
+
+    let slot = match value {
+        Value::Array(array) => match method {
+            "first" => array.first_mut().at(span)?,
+            "last" => array.last_mut().at(span)?,
+            "at" => array.at_mut(args.expect("index")?).at(span)?,
+            _ => return missing(),
+        },
+        Value::Dict(dict) => match method {
+            "at" => dict.at_mut(args.expect("index")?),
+            _ => return missing(),
+        },
+        _ => return missing(),
+    };
+
+    args.finish()?;
+    Ok(slot)
+}
+
 /// Whether a specific method is mutating.
 pub fn is_mutating(method: &str) -> bool {
     matches!(method, "push" | "pop" | "insert" | "remove")
 }
 
+/// Whether a specific method is an accessor.
+pub fn is_accessor(method: &str) -> bool {
+    matches!(method, "first" | "last" | "at")
+}
+
 /// The missing method error message.
 #[cold]
 fn missing_method(type_name: &str, method: &str) -> String {
diff --git a/src/model/str.rs b/src/model/str.rs
index d1bf9d23..9196a35a 100644
--- a/src/model/str.rs
+++ b/src/model/str.rs
@@ -42,16 +42,40 @@ impl Str {
         self
     }
 
-    /// The codepoints the string consists of.
-    pub fn codepoints(&self) -> Array {
-        self.as_str().chars().map(|c| Value::Str(c.into())).collect()
-    }
-
     /// The grapheme clusters the string consists of.
     pub fn graphemes(&self) -> Array {
         self.as_str().graphemes(true).map(|s| Value::Str(s.into())).collect()
     }
 
+    /// Extract the first grapheme cluster.
+    pub fn first(&self) -> StrResult<Self> {
+        self.0
+            .graphemes(true)
+            .next()
+            .map(Into::into)
+            .ok_or_else(string_is_empty)
+    }
+
+    /// Extract the last grapheme cluster.
+    pub fn last(&self) -> StrResult<Self> {
+        self.0
+            .graphemes(true)
+            .next_back()
+            .map(Into::into)
+            .ok_or_else(string_is_empty)
+    }
+
+    /// Extract the grapheme cluster at the given index.
+    pub fn at(&self, index: i64) -> StrResult<Self> {
+        let len = self.len();
+        let grapheme = self
+            .locate(index)
+            .filter(|&index| index <= self.0.len())
+            .and_then(|index| self.0[index..].graphemes(true).next())
+            .ok_or_else(|| out_of_bounds(index, len))?;
+        Ok(grapheme.into())
+    }
+
     /// Extract a contigous substring.
     pub fn slice(&self, start: i64, end: Option<i64>) -> StrResult<Self> {
         let len = self.len();
@@ -270,6 +294,12 @@ fn out_of_bounds(index: i64, len: i64) -> String {
     format!("string index out of bounds (index: {}, len: {})", index, len)
 }
 
+/// The error message when the string is empty.
+#[cold]
+fn string_is_empty() -> EcoString {
+    "string is empty".into()
+}
+
 /// Convert an item of std's `match_indices` to a dictionary.
 fn match_to_dict((start, text): (usize, &str)) -> Dict {
     dict! {
diff --git a/tests/ref/compiler/array.png b/tests/ref/compiler/array.png
index cbda8aee..d41e2cbb 100644
--- a/tests/ref/compiler/array.png
+++ b/tests/ref/compiler/array.png
diff --git a/tests/ref/compiler/methods-color.png b/tests/ref/compiler/color.png
index 9b65c16d..9b65c16d 100644
--- a/tests/ref/compiler/methods-color.png
+++ b/tests/ref/compiler/color.png
diff --git a/tests/ref/compiler/methods-collection.png b/tests/ref/compiler/methods-collection.png
deleted file mode 100644
index e93e2beb..00000000
--- a/tests/ref/compiler/methods-collection.png
+++ /dev/null
diff --git a/tests/typ/basics/enum.typ b/tests/typ/basics/enum.typ
index e651ca31..c1ce17b7 100644
--- a/tests/typ/basics/enum.typ
+++ b/tests/typ/basics/enum.typ
@@ -39,11 +39,14 @@
 ---
 // Test numbering with closure.
 #enum(
-   start: 4,
-   spacing: 0.65em - 3pt,
-   tight: false,
-   numbering: n => text(fill: (red, green, blue)(mod(n, 3)), numbering("A", n)),
-   [Red], [Green], [Blue],
+  start: 4,
+  spacing: 0.65em - 3pt,
+  tight: false,
+  numbering: n => text(
+    fill: (red, green, blue).at(mod(n, 3)),
+    numbering("A", n),
+  ),
+  [Red], [Green], [Blue],
 )
 
 ---
diff --git a/tests/typ/basics/terms.typ b/tests/typ/basics/terms.typ
index ba23f909..204defbf 100644
--- a/tests/typ/basics/terms.typ
+++ b/tests/typ/basics/terms.typ
@@ -40,7 +40,7 @@ No: list \
 #show terms: it => table(
   columns: 2,
   inset: 3pt,
-  ..it.items.map(item => (emph(item(0)), item(1))).flatten(),
+  ..it.items.map(item => (emph(item.at(0)), item.at(1))).flatten(),
 )
 
 / A: One letter
diff --git a/tests/typ/compiler/array.typ b/tests/typ/compiler/array.typ
index cb8433cb..ccde8598 100644
--- a/tests/typ/compiler/array.typ
+++ b/tests/typ/compiler/array.typ
@@ -24,51 +24,187 @@
      ,)}
 
 ---
+// Test the `len` method.
+#test(().len(), 0)
+#test(("A", "B", "C").len(), 3)
+
+---
 // Test lvalue and rvalue access.
 {
   let array = (1, 2)
-  array(1) += 5 + array(0)
+  array.at(1) += 5 + array.at(0)
   test(array, (1, 8))
 }
 
 ---
+// Test different lvalue method.
+{
+  let array = (1, 2, 3)
+  array.first() = 7
+  array.at(1) *= 8
+  test(array, (7, 16, 3))
+}
+
+---
 // Test rvalue out of bounds.
-// Error: 2-14 array index out of bounds (index: 5, len: 3)
-{(1, 2, 3)(5)}
+// Error: 2-17 array index out of bounds (index: 5, len: 3)
+{(1, 2, 3).at(5)}
 
 ---
 // Test lvalue out of bounds.
 {
   let array = (1, 2, 3)
-  // Error: 3-11 array index out of bounds (index: 3, len: 3)
-  array(3) = 5
+  // Error: 3-14 array index out of bounds (index: 3, len: 3)
+  array.at(3) = 5
 }
 
 ---
+// Test bad lvalue.
+// Error: 2:3-2:14 cannot mutate a temporary value
+#let array = (1, 2, 3)
+{ array.len() = 4 }
+
+---
+// Test bad lvalue.
+// Error: 2:3-2:15 type array has no method `yolo`
+#let array = (1, 2, 3)
+{ array.yolo() = 4 }
+
+---
 // Test negative indices.
 {
   let array = (1, 2, 3, 4)
-  test(array(0), 1)
-  test(array(-1), 4)
-  test(array(-2), 3)
-  test(array(-3), 2)
-  test(array(-4), 1)
+  test(array.at(0), 1)
+  test(array.at(-1), 4)
+  test(array.at(-2), 3)
+  test(array.at(-3), 2)
+  test(array.at(-4), 1)
 }
 
 ---
-// Error: 2-15 array index out of bounds (index: -4, len: 3)
-{(1, 2, 3)(-4)}
+// The the `first` and `last` methods.
+#test((1,).first(), 1)
+#test((2,).last(), 2)
+#test((1, 2, 3).first(), 1)
+#test((1, 2, 3).last(), 3)
+
+---
+// Error: 3-13 array is empty
+{ ().first() }
 
 ---
-// Test non-collection indexing.
+// Error: 3-12 array is empty
+{ ().last() }
 
+---
+// Test the `push` and `pop` methods.
 {
-  let x = 10pt
-  // Error: 3-4 expected collection, found length
-  x() = 1
+  let tasks = (a: (1, 2, 3), b: (4, 5, 6))
+  tasks.at("a").pop()
+  tasks.b.push(7)
+  test(tasks.a, (1, 2))
+  test(tasks.at("b"), (4, 5, 6, 7))
 }
 
 ---
+// Test the `insert` and `remove` methods.
+{
+  let array = (0, 1, 2, 4, 5)
+  array.insert(3, 3)
+  test(array, range(6))
+  array.remove(1)
+  test(array, (0, 2, 3, 4, 5))
+}
+
+---
+// Error: 2:17-2:19 missing argument: index
+#let numbers = ()
+{ numbers.insert() }
+---
+// Test the `slice` method.
+#test((1, 2, 3, 4).slice(2), (3, 4))
+#test(range(10).slice(2, 6), (2, 3, 4, 5))
+#test(range(10).slice(4, count: 3), (4, 5, 6))
+#test(range(10).slice(-5, count: 2), (5, 6))
+#test((1, 2, 3).slice(2, -2), ())
+#test((1, 2, 3).slice(-2, 2), (2,))
+#test((1, 2, 3).slice(-3, 2), (1, 2))
+#test("ABCD".split("").slice(1, -1).join("-"), "A-B-C-D")
+
+---
+// Error: 3-31 array index out of bounds (index: 12, len: 10)
+{ range(10).slice(9, count: 3) }
+
+---
+// Error: 3-25 array index out of bounds (index: -4, len: 3)
+{ (1, 2, 3).slice(0, -4) }
+
+---
+// Test the `position` method.
+#test(("Hi", "❤️", "Love").position(s => s == "❤️"), 1)
+#test(("Bye", "💘", "Apart").position(s => s == "❤️"), none)
+#test(("A", "B", "CDEF", "G").position(v => v.len() > 2), 2)
+
+---
+// Test the `filter` method.
+#test(().filter(even), ())
+#test((1, 2, 3, 4).filter(even), (2, 4))
+#test((7, 3, 2, 5, 1).filter(x => x < 5), (3, 2, 1))
+
+---
+// Test the `map` method.
+#test(().map(x => x * 2), ())
+#test((2, 3).map(x => x * 2), (4, 6))
+
+---
+// Test the `fold` method.
+#test(().fold("hi", grid), "hi")
+#test((1, 2, 3, 4).fold(0, (s, x) => s + x), 10)
+
+---
+// Error: 21-31 function must have exactly two parameters
+{ (1, 2, 3).fold(0, () => none) }
+
+---
+// Test the `rev` method.
+#test(range(3).rev(), (2, 1, 0))
+
+---
+// Test the `join` method.
+#test(().join(), none)
+#test((1,).join(), 1)
+#test(("a", "b", "c").join(), "abc")
+#test("(" + ("a", "b", "c").join(", ") + ")", "(a, b, c)")
+
+---
+// Error: 2-22 cannot join boolean with boolean
+{(true, false).join()}
+
+---
+// Error: 2-20 cannot join string with integer
+{("a", "b").join(1)}
+
+---
+// Test joining content.
+// Ref: true
+{([One], [Two], [Three]).join([, ], last: [ and ])}.
+
+---
+// Test the `sorted` method.
+#test(().sorted(), ())
+#test(((true, false) * 10).sorted(), (false,) * 10 + (true,) * 10)
+#test(("it", "the", "hi", "text").sorted(), ("hi", "it", "text", "the"))
+#test((2, 1, 3, 10, 5, 8, 6, -7, 2).sorted(), (-7, 1, 2, 2, 3, 5, 6, 8, 10))
+
+---
+// Error: 2-26 cannot order content and content
+{([Hi], [There]).sorted()}
+
+---
+// Error: 2-18 array index out of bounds (index: -4, len: 3)
+{(1, 2, 3).at(-4)}
+
+---
 // Error: 3 expected closing paren
 {(}
 
diff --git a/tests/typ/compiler/call.typ b/tests/typ/compiler/call.typ
index dc582c9c..7ea0a998 100644
--- a/tests/typ/compiler/call.typ
+++ b/tests/typ/compiler/call.typ
@@ -48,25 +48,25 @@
 #set text(family: "Arial", family: "Helvetica")
 
 ---
-// Error: 2-6 expected callable or collection, found boolean
+// Error: 2-6 expected function, found boolean
 {true()}
 
 ---
 #let x = "x"
 
-// Error: 1-3 expected callable or collection, found string
+// Error: 1-3 expected function, found string
 #x()
 
 ---
 #let f(x) = x
 
-// Error: 1-6 expected callable or collection, found integer
+// Error: 1-6 expected function, found integer
 #f(1)(2)
 
 ---
 #let f(x) = x
 
-// Error: 1-6 expected callable or collection, found content
+// Error: 1-6 expected function, found content
 #f[1](2)
 
 ---
diff --git a/tests/typ/compiler/methods-color.typ b/tests/typ/compiler/color.typ
index 3b165d14..3b165d14 100644
--- a/tests/typ/compiler/methods-color.typ
+++ b/tests/typ/compiler/color.typ
diff --git a/tests/typ/compiler/dict.typ b/tests/typ/compiler/dict.typ
index d791f77b..0170cb8b 100644
--- a/tests/typ/compiler/dict.typ
+++ b/tests/typ/compiler/dict.typ
@@ -12,17 +12,17 @@
 #dict
 
 #test(dict.normal, 1)
-#test(dict("spacy key"), 2)
+#test(dict.at("spacy key"), 2)
 
 ---
 // Test lvalue and rvalue access.
 {
   let dict = (a: 1, "b b": 1)
-  dict("b b") += 1
+  dict.at("b b") += 1
   dict.state = (ok: true, err: false)
   test(dict, (a: 1, "b b": 2, state: (ok: true, err: false)))
   test(dict.state.ok, true)
-  dict("state").ok = false
+  dict.at("state").ok = false
   test(dict.state.ok, false)
   test(dict.state.err, false)
 }
@@ -31,19 +31,31 @@
 // Test rvalue missing key.
 {
   let dict = (a: 1, b: 2)
-  // Error: 11-20 dictionary does not contain key "c"
-  let x = dict("c")
+  // Error: 11-23 dictionary does not contain key "c"
+  let x = dict.at("c")
 }
 
 ---
 // Missing lvalue is automatically none-initialized.
 {
   let dict = (:)
-  dict("b") += 1
+  dict.at("b") += 1
   test(dict, (b: 1))
 }
 
 ---
+// Test dictionary methods.
+#let dict = (a: 3, c: 2, b: 1)
+#test("c" in dict, true)
+#test(dict.len(), 3)
+#test(dict.values(), (3, 1, 2))
+#test(dict.pairs((k, v) => k + str(v)).join(), "a3b1c2")
+
+{ dict.remove("c") }
+#test("c" in dict, false)
+#test(dict, (a: 3, b: 1))
+
+---
 // Error: 24-32 pair has duplicate key
 {(first: 1, second: 2, first: 3)}
 
@@ -65,7 +77,7 @@
 
 ---
 // Error: 3-15 cannot mutate a temporary value
-{ (key: value).other = "some" }
+{ (key: "val").other = "some" }
 
 ---
 {
diff --git a/tests/typ/compiler/methods-collection.typ b/tests/typ/compiler/methods-collection.typ
deleted file mode 100644
index fcebf640..00000000
--- a/tests/typ/compiler/methods-collection.typ
+++ /dev/null
@@ -1,115 +0,0 @@
-// Test the collection methods.
-// Ref: false
-
----
-// Test the `len` method.
-#test(().len(), 0)
-#test(("A", "B", "C").len(), 3)
-#test("Hello World!".len(), 12)
-#test((a: 1, b: 2).len(), 2)
-
----
-// The the `first` and `last` methods.
-#test(().first(), none)
-#test(().last(), none)
-#test((1,).first(), 1)
-#test((2,).last(), 2)
-#test((1, 2, 3).first(), 1)
-#test((1, 2, 3).last(), 3)
-
----
-// Test the `push` and `pop` methods.
-{
-  let tasks = (a: (1, 2, 3), b: (4, 5, 6))
-  tasks("a").pop()
-  tasks("b").push(7)
-  test(tasks("a"), (1, 2))
-  test(tasks("b"), (4, 5, 6, 7))
-}
-
----
-// Test the `insert` and `remove` methods.
-{
-  let array = (0, 1, 2, 4, 5)
-  array.insert(3, 3)
-  test(array, range(6))
-  array.remove(1)
-  test(array, (0, 2, 3, 4, 5))
-}
-
----
-// Error: 2:17-2:19 missing argument: index
-#let numbers = ()
-{ numbers.insert() }
-
----
-// Test the `slice` method.
-#test((1, 2, 3, 4).slice(2), (3, 4))
-#test(range(10).slice(2, 6), (2, 3, 4, 5))
-#test(range(10).slice(4, count: 3), (4, 5, 6))
-#test(range(10).slice(-5, count: 2), (5, 6))
-#test((1, 2, 3).slice(2, -2), ())
-#test((1, 2, 3).slice(-2, 2), (2,))
-#test((1, 2, 3).slice(-3, 2), (1, 2))
-#test("ABCD".split("").slice(1, -1).join("-"), "A-B-C-D")
-
----
-// Error: 3-31 array index out of bounds (index: 12, len: 10)
-{ range(10).slice(9, count: 3) }
-
----
-// Error: 3-25 array index out of bounds (index: -4, len: 3)
-{ (1, 2, 3).slice(0, -4) }
-
----
-// Test the `position` method.
-#test(("Hi", "❤️", "Love").position(s => s == "❤️"), 1)
-#test(("Bye", "💘", "Apart").position(s => s == "❤️"), none)
-#test(("A", "B", "CDEF", "G").position(v => v.len() > 2), 2)
-
----
-// Test the `rev` method.
-#test(range(3).rev(), (2, 1, 0))
-
----
-// Test the `join` method.
-#test(().join(), none)
-#test((1,).join(), 1)
-#test(("a", "b", "c").join(), "abc")
-#test("(" + ("a", "b", "c").join(", ") + ")", "(a, b, c)")
-
----
-// Error: 2-22 cannot join boolean with boolean
-{(true, false).join()}
-
----
-// Error: 2-20 cannot join string with integer
-{("a", "b").join(1)}
-
----
-// Test joining content.
-// Ref: true
-{([One], [Two], [Three]).join([, ], last: [ and ])}.
-
----
-// Test the `sorted` method.
-#test(().sorted(), ())
-#test(((true, false) * 10).sorted(), (false,) * 10 + (true,) * 10)
-#test(("it", "the", "hi", "text").sorted(), ("hi", "it", "text", "the"))
-#test((2, 1, 3, 10, 5, 8, 6, -7, 2).sorted(), (-7, 1, 2, 2, 3, 5, 6, 8, 10))
-
----
-// Error: 2-26 cannot order content and content
-{([Hi], [There]).sorted()}
-
----
-// Test dictionary methods.
-#let dict = (a: 3, c: 2, b: 1)
-#test("c" in dict, true)
-#test(dict.len(), 3)
-#test(dict.values(), (3, 1, 2))
-#test(dict.pairs((k, v) => k + str(v)).join(), "a3b1c2")
-
-{ dict.remove("c") }
-#test("c" in dict, false)
-#test(dict, (a: 3, b: 1))
diff --git a/tests/typ/compiler/methods.typ b/tests/typ/compiler/methods.typ
index 07f6e410..f468320b 100644
--- a/tests/typ/compiler/methods.typ
+++ b/tests/typ/compiler/methods.typ
@@ -9,7 +9,7 @@
 // Test mutating indexed value.
 {
   let matrix = (((1,), (2,)), ((3,), (4,)))
-  matrix(1)(0).push(5)
+  matrix.at(1).at(0).push(5)
   test(matrix, (((1,), (2,)), ((3, 5), (4,))))
 }
 
diff --git a/tests/typ/compiler/ops-invalid.typ b/tests/typ/compiler/ops-invalid.typ
index 3d41a3d1..d51e42fb 100644
--- a/tests/typ/compiler/ops-invalid.typ
+++ b/tests/typ/compiler/ops-invalid.typ
@@ -90,14 +90,14 @@
 {
   let x = 2
   for _ in range(61) {
-    x *= 2
+    (x) *= 2
   }
   // Error: 4-18 cannot repeat this string 4611686018427387904 times
   {x * "abcdefgh"}
 }
 
 ---
-// Error: 3-6 cannot mutate a temporary value
+// Error: 4-5 unknown variable
 { (x) = "" }
 
 ---
@@ -105,6 +105,15 @@
 { 1 + 2 += 3 }
 
 ---
+// Error: 2:2-2:7 cannot apply 'not' to string
+#let x = "Hey"
+{not x = "a"}
+
+---
+// Error: 7-8 unknown variable
+{ 1 + x += 3 }
+
+---
 // Error: 3-4 unknown variable
 { z = 1 }
 
diff --git a/tests/typ/compiler/ops-prec.typ b/tests/typ/compiler/ops-prec.typ
index 23afcc5f..eba0c8a9 100644
--- a/tests/typ/compiler/ops-prec.typ
+++ b/tests/typ/compiler/ops-prec.typ
@@ -12,8 +12,10 @@
 #test("a" == "a" and 2 < 3, true)
 #test(not "b" == "b", false)
 
+---
 // Assignment binds stronger than boolean operations.
-// Error: 2-7 cannot mutate a temporary value
+// Error: 2:2-2:7 cannot mutate a temporary value
+#let x = false
 {not x = "a"}
 
 ---
diff --git a/tests/typ/compiler/set.typ b/tests/typ/compiler/set.typ
index 7414ad5e..034bfab8 100644
--- a/tests/typ/compiler/set.typ
+++ b/tests/typ/compiler/set.typ
@@ -40,7 +40,7 @@ Hello *{x}*
 // Test relative path resolving in layout phase.
 #let choice = ("monkey.svg", "rhino.png", "tiger.jpg")
 #set enum(numbering: n => {
-  let path = "../../res/" + choice(n - 1)
+  let path = "../../res/" + choice.at(n - 1)
   move(dy: -0.15em, image(path, width: 1em, height: 1em))
 })
 
diff --git a/tests/typ/compiler/methods-str.typ b/tests/typ/compiler/string.typ
index aead4aa4..8ac515a5 100644
--- a/tests/typ/compiler/methods-str.typ
+++ b/tests/typ/compiler/string.typ
@@ -2,6 +2,35 @@
 // Ref: false
 
 ---
+// Test the `len` method.
+#test("Hello World!".len(), 12)
+
+---
+// Test the `first` and `last` methods.
+#test("Hello".first(), "H")
+#test("Hello".last(), "o")
+#test("🏳️‍🌈A🏳️‍⚧️".first(), "🏳️‍🌈")
+#test("🏳️‍🌈A🏳️‍⚧️".last(), "🏳️‍⚧️")
+
+---
+// Error: 3-13 string is empty
+{ "".first() }
+
+---
+// Error: 3-12 string is empty
+{ "".last() }
+
+---
+// Test the `at` method.
+#test("Hello".at(1), "e")
+#test("Hello".at(4), "o")
+#test("Hey: 🏳️‍🌈 there!".at(5), "🏳️‍🌈")
+
+---
+// Error: 3-16 string index out of bounds (index: 5, len: 5)
+{ "Hello".at(5) }
+
+---
 // Test the `slice` method.
 #test("abc".slice(1, 2), "b")
 #test("abc🏡def".slice(2, 7), "c🏡")
@@ -57,7 +86,7 @@
   let time = 0
   for match in text.matches(regex("(\d+):(\d+)")) {
     let caps = match.captures
-    time += 60 * int(caps(0)) + int(caps(1))
+    time += 60 * int(caps.at(0)) + int(caps.at(1))
   }
   str(int(time / 60)) + ":" + str(mod(time, 60))
 }
diff --git a/tests/typ/compute/data.typ b/tests/typ/compute/data.typ
index 5a0f76c6..dc563022 100644
--- a/tests/typ/compute/data.typ
+++ b/tests/typ/compute/data.typ
@@ -19,8 +19,8 @@
 // Ref: true
 #set page(width: auto)
 #let data = csv("/res/zoo.csv")
-#let cells = data(0).map(strong) + data.slice(1).flatten()
-#table(columns: data(0).len(), ..cells)
+#let cells = data.at(0).map(strong) + data.slice(1).flatten()
+#table(columns: data.at(0).len(), ..cells)
 
 ---
 // Error: 6-16 file not found (searched at typ/compute/nope.csv)
@@ -34,8 +34,8 @@
 // Test reading JSON data.
 #let data = json("/res/zoo.json")
 #test(data.len(), 3)
-#test(data(0).name, "Debby")
-#test(data(2).weight, 150)
+#test(data.at(0).name, "Debby")
+#test(data.at(2).weight, 150)
 
 ---
 // Error: 7-22 failed to parse json file: syntax error in line 3
diff --git a/tests/typ/layout/repeat.typ b/tests/typ/layout/repeat.typ
index 3b5459c9..82d64b94 100644
--- a/tests/typ/layout/repeat.typ
+++ b/tests/typ/layout/repeat.typ
@@ -12,7 +12,7 @@
 )
 
 #for section in sections [
-  #section(0) #repeat[.] #section(1) \
+  {section.at(0)} #repeat[.] {section.at(1)} \
 ]
 
 ---