Group and block expressions, unary plus 🧩

8 files changed, 396 insertions, 340 deletions

diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index efa74596..32a7d6ba 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -4,6 +4,7 @@
 mod value;
 mod call;
 mod context;
+mod ops;
 mod scope;
 mod state;
 
@@ -45,17 +46,6 @@ pub trait Eval {
     fn eval(self, ctx: &mut EvalContext) -> Self::Output;
 }
 
-impl<'a, T> Eval for &'a Box<Spanned<T>>
-where
-    Spanned<&'a T>: Eval,
-{
-    type Output = <Spanned<&'a T> as Eval>::Output;
-
-    fn eval(self, ctx: &mut EvalContext) -> Self::Output {
-        (**self).as_ref().eval(ctx)
-    }
-}
-
 impl Eval for &[Spanned<Node>] {
     type Output = ();
 
@@ -171,6 +161,8 @@ impl Eval for Spanned<&Expr> {
             Expr::Array(v) => Value::Array(v.with_span(self.span).eval(ctx)),
             Expr::Dict(v) => Value::Dict(v.with_span(self.span).eval(ctx)),
             Expr::Template(v) => Value::Template(v.clone()),
+            Expr::Group(v) => v.as_ref().with_span(self.span).eval(ctx),
+            Expr::Block(v) => v.as_ref().with_span(self.span).eval(ctx),
         }
     }
 }
@@ -179,7 +171,7 @@ impl Eval for Spanned<&ExprUnary> {
     type Output = Value;
 
     fn eval(self, ctx: &mut EvalContext) -> Self::Output {
-        let value = self.v.expr.eval(ctx);
+        let value = (*self.v.expr).as_ref().eval(ctx);
 
         if let Value::Error = value {
             return Value::Error;
@@ -187,7 +179,8 @@ impl Eval for Spanned<&ExprUnary> {
 
         let span = self.v.op.span.join(self.v.expr.span);
         match self.v.op.v {
-            UnOp::Neg => neg(ctx, span, value),
+            UnOp::Pos => ops::pos(ctx, span, value),
+            UnOp::Neg => ops::neg(ctx, span, value),
         }
     }
 }
@@ -196,8 +189,8 @@ impl Eval for Spanned<&ExprBinary> {
     type Output = Value;
 
     fn eval(self, ctx: &mut EvalContext) -> Self::Output {
-        let lhs = self.v.lhs.eval(ctx);
-        let rhs = self.v.rhs.eval(ctx);
+        let lhs = (*self.v.lhs).as_ref().eval(ctx);
+        let rhs = (*self.v.rhs).as_ref().eval(ctx);
 
         if lhs == Value::Error || rhs == Value::Error {
             return Value::Error;
@@ -205,10 +198,10 @@ impl Eval for Spanned<&ExprBinary> {
 
         let span = self.v.lhs.span.join(self.v.rhs.span);
         match self.v.op.v {
-            BinOp::Add => add(ctx, span, lhs, rhs),
-            BinOp::Sub => sub(ctx, span, lhs, rhs),
-            BinOp::Mul => mul(ctx, span, lhs, rhs),
-            BinOp::Div => div(ctx, span, lhs, rhs),
+            BinOp::Add => ops::add(ctx, span, lhs, rhs),
+            BinOp::Sub => ops::sub(ctx, span, lhs, rhs),
+            BinOp::Mul => ops::mul(ctx, span, lhs, rhs),
+            BinOp::Div => ops::div(ctx, span, lhs, rhs),
         }
     }
 }
@@ -231,172 +224,3 @@ impl Eval for Spanned<&ExprDict> {
             .collect()
     }
 }
-
-/// Compute the negation of a value.
-fn neg(ctx: &mut EvalContext, span: Span, value: Value) -> Value {
-    use Value::*;
-    match value {
-        Int(v) => Int(-v),
-        Float(v) => Float(-v),
-        Length(v) => Length(-v),
-        Relative(v) => Relative(-v),
-        Linear(v) => Linear(-v),
-        v => {
-            ctx.diag(error!(span, "cannot negate {}", v.type_name()));
-            Value::Error
-        }
-    }
-}
-
-/// Compute the sum of two values.
-fn add(ctx: &mut EvalContext, span: Span, lhs: Value, rhs: Value) -> Value {
-    use Value::*;
-    match (lhs, rhs) {
-        // Numbers to themselves.
-        (Int(a), Int(b)) => Int(a + b),
-        (Int(a), Float(b)) => Float(a as f64 + b),
-        (Float(a), Int(b)) => Float(a + b as f64),
-        (Float(a), Float(b)) => Float(a + b),
-
-        // Lengths, relatives and linears to themselves.
-        (Length(a), Length(b)) => Length(a + b),
-        (Length(a), Relative(b)) => Linear(a + b),
-        (Length(a), Linear(b)) => Linear(a + b),
-
-        (Relative(a), Length(b)) => Linear(a + b),
-        (Relative(a), Relative(b)) => Relative(a + b),
-        (Relative(a), Linear(b)) => Linear(a + b),
-
-        (Linear(a), Length(b)) => Linear(a + b),
-        (Linear(a), Relative(b)) => Linear(a + b),
-        (Linear(a), Linear(b)) => Linear(a + b),
-
-        // Complex data types to themselves.
-        (Str(a), Str(b)) => Str(a + &b),
-        (Array(a), Array(b)) => Array(concat(a, b)),
-        (Dict(a), Dict(b)) => Dict(concat(a, b)),
-        (Template(a), Template(b)) => Template(concat(a, b)),
-
-        (a, b) => {
-            ctx.diag(error!(
-                span,
-                "cannot add {} and {}",
-                a.type_name(),
-                b.type_name()
-            ));
-            Value::Error
-        }
-    }
-}
-
-/// Compute the difference of two values.
-fn sub(ctx: &mut EvalContext, span: Span, lhs: Value, rhs: Value) -> Value {
-    use Value::*;
-    match (lhs, rhs) {
-        // Numbers from themselves.
-        (Int(a), Int(b)) => Int(a - b),
-        (Int(a), Float(b)) => Float(a as f64 - b),
-        (Float(a), Int(b)) => Float(a - b as f64),
-        (Float(a), Float(b)) => Float(a - b),
-
-        // Lengths, relatives and linears from themselves.
-        (Length(a), Length(b)) => Length(a - b),
-        (Length(a), Relative(b)) => Linear(a - b),
-        (Length(a), Linear(b)) => Linear(a - b),
-        (Relative(a), Length(b)) => Linear(a - b),
-        (Relative(a), Relative(b)) => Relative(a - b),
-        (Relative(a), Linear(b)) => Linear(a - b),
-        (Linear(a), Length(b)) => Linear(a - b),
-        (Linear(a), Relative(b)) => Linear(a - b),
-        (Linear(a), Linear(b)) => Linear(a - b),
-
-        (a, b) => {
-            ctx.diag(error!(
-                span,
-                "cannot subtract {1} from {0}",
-                a.type_name(),
-                b.type_name()
-            ));
-            Value::Error
-        }
-    }
-}
-
-/// Compute the product of two values.
-fn mul(ctx: &mut EvalContext, span: Span, lhs: Value, rhs: Value) -> Value {
-    use Value::*;
-    match (lhs, rhs) {
-        // Numbers with themselves.
-        (Int(a), Int(b)) => Int(a * b),
-        (Int(a), Float(b)) => Float(a as f64 * b),
-        (Float(a), Int(b)) => Float(a * b as f64),
-        (Float(a), Float(b)) => Float(a * b),
-
-        // Lengths, relatives and linears with numbers.
-        (Length(a), Int(b)) => Length(a * b as f64),
-        (Length(a), Float(b)) => Length(a * b),
-        (Int(a), Length(b)) => Length(a as f64 * b),
-        (Float(a), Length(b)) => Length(a * b),
-        (Relative(a), Int(b)) => Relative(a * b as f64),
-        (Relative(a), Float(b)) => Relative(a * b),
-        (Int(a), Relative(b)) => Relative(a as f64 * b),
-        (Float(a), Relative(b)) => Relative(a * b),
-        (Linear(a), Int(b)) => Linear(a * b as f64),
-        (Linear(a), Float(b)) => Linear(a * b),
-        (Int(a), Linear(b)) => Linear(a as f64 * b),
-        (Float(a), Linear(b)) => Linear(a * b),
-
-        // Integers with strings.
-        (Int(a), Str(b)) => Str(b.repeat(0.max(a) as usize)),
-        (Str(a), Int(b)) => Str(a.repeat(0.max(b) as usize)),
-
-        (a, b) => {
-            ctx.diag(error!(
-                span,
-                "cannot multiply {} with {}",
-                a.type_name(),
-                b.type_name()
-            ));
-            Value::Error
-        }
-    }
-}
-
-/// Compute the quotient of two values.
-fn div(ctx: &mut EvalContext, span: Span, lhs: Value, rhs: Value) -> Value {
-    use Value::*;
-    match (lhs, rhs) {
-        // Numbers by themselves.
-        (Int(a), Int(b)) => Float(a as f64 / b as f64),
-        (Int(a), Float(b)) => Float(a as f64 / b),
-        (Float(a), Int(b)) => Float(a / b as f64),
-        (Float(a), Float(b)) => Float(a / b),
-
-        // Lengths by numbers.
-        (Length(a), Int(b)) => Length(a / b as f64),
-        (Length(a), Float(b)) => Length(a / b),
-        (Relative(a), Int(b)) => Relative(a / b as f64),
-        (Relative(a), Float(b)) => Relative(a / b),
-        (Linear(a), Int(b)) => Linear(a / b as f64),
-        (Linear(a), Float(b)) => Linear(a / b),
-
-        (a, b) => {
-            ctx.diag(error!(
-                span,
-                "cannot divide {} by {}",
-                a.type_name(),
-                b.type_name()
-            ));
-            Value::Error
-        }
-    }
-}
-
-/// Concatenate two collections.
-fn concat<T, A>(mut a: T, b: T) -> T
-where
-    T: Extend<A> + IntoIterator<Item = A>,
-{
-    a.extend(b);
-    a
-}
diff --git a/src/eval/ops.rs b/src/eval/ops.rs
new file mode 100644
index 00000000..0a273da5
--- /dev/null
+++ b/src/eval/ops.rs
@@ -0,0 +1,183 @@
+use super::*;
+
+/// Apply plus operator to a value.
+pub fn pos(ctx: &mut EvalContext, span: Span, value: Value) -> Value {
+    if value.is_numeric() {
+        value
+    } else {
+        ctx.diag(error!(
+            span,
+            "cannot apply plus operator to {}",
+            value.type_name()
+        ));
+        Value::Error
+    }
+}
+
+/// Compute the negation of a value.
+pub fn neg(ctx: &mut EvalContext, span: Span, value: Value) -> Value {
+    use Value::*;
+    match value {
+        Int(v) => Int(-v),
+        Float(v) => Float(-v),
+        Length(v) => Length(-v),
+        Angle(v) => Angle(-v),
+        Relative(v) => Relative(-v),
+        Linear(v) => Linear(-v),
+        v => {
+            ctx.diag(error!(span, "cannot negate {}", v.type_name()));
+            Value::Error
+        }
+    }
+}
+
+/// Compute the sum of two values.
+pub fn add(ctx: &mut EvalContext, span: Span, lhs: Value, rhs: Value) -> Value {
+    use Value::*;
+    match (lhs, rhs) {
+        // Numeric types to themselves.
+        (Int(a), Int(b)) => Int(a + b),
+        (Int(a), Float(b)) => Float(a as f64 + b),
+        (Float(a), Int(b)) => Float(a + b as f64),
+        (Float(a), Float(b)) => Float(a + b),
+        (Angle(a), Angle(b)) => Angle(a + b),
+        (Length(a), Length(b)) => Length(a + b),
+        (Length(a), Relative(b)) => Linear(a + b),
+        (Length(a), Linear(b)) => Linear(a + b),
+        (Relative(a), Length(b)) => Linear(a + b),
+        (Relative(a), Relative(b)) => Relative(a + b),
+        (Relative(a), Linear(b)) => Linear(a + b),
+        (Linear(a), Length(b)) => Linear(a + b),
+        (Linear(a), Relative(b)) => Linear(a + b),
+        (Linear(a), Linear(b)) => Linear(a + b),
+
+        // Complex data types to themselves.
+        (Str(a), Str(b)) => Str(a + &b),
+        (Array(a), Array(b)) => Array(concat(a, b)),
+        (Dict(a), Dict(b)) => Dict(concat(a, b)),
+        (Template(a), Template(b)) => Template(concat(a, b)),
+
+        (a, b) => {
+            ctx.diag(error!(
+                span,
+                "cannot add {} and {}",
+                a.type_name(),
+                b.type_name()
+            ));
+            Value::Error
+        }
+    }
+}
+
+/// Compute the difference of two values.
+pub fn sub(ctx: &mut EvalContext, span: Span, lhs: Value, rhs: Value) -> Value {
+    use Value::*;
+    match (lhs, rhs) {
+        // Numbers from themselves.
+        (Int(a), Int(b)) => Int(a - b),
+        (Int(a), Float(b)) => Float(a as f64 - b),
+        (Float(a), Int(b)) => Float(a - b as f64),
+        (Float(a), Float(b)) => Float(a - b),
+        (Angle(a), Angle(b)) => Angle(a - b),
+        (Length(a), Length(b)) => Length(a - b),
+        (Length(a), Relative(b)) => Linear(a - b),
+        (Length(a), Linear(b)) => Linear(a - b),
+        (Relative(a), Length(b)) => Linear(a - b),
+        (Relative(a), Relative(b)) => Relative(a - b),
+        (Relative(a), Linear(b)) => Linear(a - b),
+        (Linear(a), Length(b)) => Linear(a - b),
+        (Linear(a), Relative(b)) => Linear(a - b),
+        (Linear(a), Linear(b)) => Linear(a - b),
+
+        (a, b) => {
+            ctx.diag(error!(
+                span,
+                "cannot subtract {1} from {0}",
+                a.type_name(),
+                b.type_name()
+            ));
+            Value::Error
+        }
+    }
+}
+
+/// Compute the product of two values.
+pub fn mul(ctx: &mut EvalContext, span: Span, lhs: Value, rhs: Value) -> Value {
+    use Value::*;
+    match (lhs, rhs) {
+        // Numeric types with numbers.
+        (Int(a), Int(b)) => Int(a * b),
+        (Int(a), Float(b)) => Float(a as f64 * b),
+        (Float(a), Int(b)) => Float(a * b as f64),
+        (Float(a), Float(b)) => Float(a * b),
+        (Length(a), Int(b)) => Length(a * b as f64),
+        (Length(a), Float(b)) => Length(a * b),
+        (Int(a), Length(b)) => Length(a as f64 * b),
+        (Float(a), Length(b)) => Length(a * b),
+        (Angle(a), Int(b)) => Angle(a * b as f64),
+        (Angle(a), Float(b)) => Angle(a * b),
+        (Int(a), Angle(b)) => Angle(a as f64 * b),
+        (Float(a), Angle(b)) => Angle(a * b),
+        (Relative(a), Int(b)) => Relative(a * b as f64),
+        (Relative(a), Float(b)) => Relative(a * b),
+        (Int(a), Relative(b)) => Relative(a as f64 * b),
+        (Float(a), Relative(b)) => Relative(a * b),
+        (Linear(a), Int(b)) => Linear(a * b as f64),
+        (Linear(a), Float(b)) => Linear(a * b),
+        (Int(a), Linear(b)) => Linear(a as f64 * b),
+        (Float(a), Linear(b)) => Linear(a * b),
+
+        // Integers with strings.
+        (Int(a), Str(b)) => Str(b.repeat(0.max(a) as usize)),
+        (Str(a), Int(b)) => Str(a.repeat(0.max(b) as usize)),
+
+        (a, b) => {
+            ctx.diag(error!(
+                span,
+                "cannot multiply {} with {}",
+                a.type_name(),
+                b.type_name()
+            ));
+            Value::Error
+        }
+    }
+}
+
+/// Compute the quotient of two values.
+pub fn div(ctx: &mut EvalContext, span: Span, lhs: Value, rhs: Value) -> Value {
+    use Value::*;
+    match (lhs, rhs) {
+        // Numeric types by numbers.
+        (Int(a), Int(b)) => Float(a as f64 / b as f64),
+        (Int(a), Float(b)) => Float(a as f64 / b),
+        (Float(a), Int(b)) => Float(a / b as f64),
+        (Float(a), Float(b)) => Float(a / b),
+        (Length(a), Int(b)) => Length(a / b as f64),
+        (Length(a), Float(b)) => Length(a / b),
+        (Angle(a), Int(b)) => Angle(a / b as f64),
+        (Angle(a), Float(b)) => Angle(a / b),
+        (Relative(a), Int(b)) => Relative(a / b as f64),
+        (Relative(a), Float(b)) => Relative(a / b),
+        (Linear(a), Int(b)) => Linear(a / b as f64),
+        (Linear(a), Float(b)) => Linear(a / b),
+
+        (a, b) => {
+            ctx.diag(error!(
+                span,
+                "cannot divide {} by {}",
+                a.type_name(),
+                b.type_name()
+            ));
+            Value::Error
+        }
+    }
+}
+
+/// Concatenate two collections.
+fn concat<T, A>(mut a: T, b: T) -> T
+where
+    T: Extend<A> + IntoIterator<Item = A>,
+{
+    a.extend(b);
+    a
+}
diff --git a/src/eval/value.rs b/src/eval/value.rs
index d3b2688b..13548c87 100644
--- a/src/eval/value.rs
+++ b/src/eval/value.rs
@@ -8,7 +8,7 @@ use super::{Args, Eval, EvalContext};
 use crate::color::Color;
 use crate::geom::{Angle, Length, Linear, Relative};
 use crate::pretty::{pretty, Pretty, Printer};
-use crate::syntax::{pretty_template_expr, Spanned, Tree, WithSpan};
+use crate::syntax::{Spanned, Tree, WithSpan};
 
 /// A computational value.
 #[derive(Debug, Clone, PartialEq)]
@@ -77,6 +77,18 @@ impl Value {
             Self::Error => "error",
         }
     }
+
+    /// Whether the value is numeric.
+    pub fn is_numeric(&self) -> bool {
+        matches!(self,
+            Value::Int(_)
+            | Value::Float(_)
+            | Value::Length(_)
+            | Value::Angle(_)
+            | Value::Relative(_)
+            | Value::Linear(_)
+        )
+    }
 }
 
 impl Eval for &Value {
@@ -112,9 +124,13 @@ impl Pretty for Value {
             Value::Linear(v) => write!(p, "{}", v).unwrap(),
             Value::Color(v) => write!(p, "{}", v).unwrap(),
             Value::Str(v) => write!(p, "{:?}", v).unwrap(),
-            Value::Array(array) => array.pretty(p),
-            Value::Dict(dict) => dict.pretty(p),
-            Value::Template(template) => pretty_template_expr(template, p),
+            Value::Array(v) => v.pretty(p),
+            Value::Dict(v) => v.pretty(p),
+            Value::Template(v) => {
+                p.push_str("[");
+                v.pretty(p);
+                p.push_str("]");
+            }
             Value::Func(v) => v.pretty(p),
             Value::Any(v) => v.pretty(p),
             Value::Error => p.push_str("(error)"),
diff --git a/src/parse/collection.rs b/src/parse/collection.rs
index 98d4219f..ca05b998 100644
--- a/src/parse/collection.rs
+++ b/src/parse/collection.rs
@@ -59,7 +59,7 @@ fn argument(p: &mut Parser) -> Option<Argument> {
             p.deco(Deco::Name.with_span(name.span));
             Some(Argument::Named(Named { name, expr }))
         } else {
-            p.diag(error!(first.span, "name must be identifier"));
+            p.diag(error!(first.span, "expected identifier"));
             expr(p);
             None
         }
@@ -93,7 +93,7 @@ impl State {
     fn into_expr(self) -> Expr {
         match self {
             Self::Unknown => Expr::Array(vec![]),
-            Self::Expr(expr) => expr.v,
+            Self::Expr(expr) => Expr::Group(Box::new(expr.v)),
             Self::Array(array) => Expr::Array(array),
             Self::Dict(dict) => Expr::Dict(dict),
         }
diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index ee799159..a66660e5 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -51,12 +51,12 @@ fn node(p: &mut Parser, at_start: bool) -> Option<Node> {
     let node = match p.peek()? {
         // Bracket call.
         Token::LeftBracket => {
-            return Some(Node::Expr(Expr::Call(bracket_call(p))));
+            return Some(Node::Expr(bracket_call(p)));
         }
 
         // Code block.
         Token::LeftBrace => {
-            return Some(Node::Expr(code_block(p)?));
+            return Some(Node::Expr(block(p)?));
         }
 
         // Markup.
@@ -154,7 +154,7 @@ fn unicode_escape(p: &mut Parser, token: TokenUnicodeEscape) -> String {
 }
 
 /// Parse a bracketed function call.
-fn bracket_call(p: &mut Parser) -> ExprCall {
+fn bracket_call(p: &mut Parser) -> Expr {
     p.push_mode(TokenMode::Code);
     p.start_group(Group::Bracket);
 
@@ -184,7 +184,7 @@ fn bracket_call(p: &mut Parser) -> ExprCall {
         inner = top;
     }
 
-    inner.v
+    Expr::Call(inner.v)
 }
 
 /// Parse one subheader of a bracketed function call.
@@ -218,8 +218,8 @@ fn bracket_body(p: &mut Parser) -> Tree {
     tree
 }
 
-/// Parse a code block: `{...}`.
-fn code_block(p: &mut Parser) -> Option<Expr> {
+/// Parse a block expression: `{...}`.
+fn block(p: &mut Parser) -> Option<Expr> {
     p.push_mode(TokenMode::Code);
     p.start_group(Group::Brace);
     let expr = expr(p);
@@ -228,7 +228,7 @@ fn code_block(p: &mut Parser) -> Option<Expr> {
     }
     p.pop_mode();
     p.end_group();
-    expr
+    Some(Expr::Block(Box::new(expr?)))
 }
 
 /// Parse an expression: `term (+ term)*`.
@@ -277,6 +277,7 @@ fn binops(
 /// Parse a factor of the form `-?value`.
 fn factor(p: &mut Parser) -> Option<Expr> {
     let op = |token| match token {
+        Token::Plus => Some(UnOp::Pos),
         Token::Hyph => Some(UnOp::Neg),
         _ => None,
     };
@@ -294,12 +295,12 @@ fn value(p: &mut Parser) -> Option<Expr> {
     let expr = match p.peek() {
         // Template.
         Some(Token::LeftBracket) => {
-            return Some(Expr::Template(template(p)));
+            return Some(template(p));
         }
 
         // Nested block.
         Some(Token::LeftBrace) => {
-            return code_block(p);
+            return block(p);
         }
 
         // Dictionary or just a parenthesized expression.
@@ -313,7 +314,7 @@ fn value(p: &mut Parser) -> Option<Expr> {
             let ident = Ident(id.into());
             if p.peek() == Some(Token::LeftParen) {
                 let name = ident.with_span(p.peek_span());
-                return Some(Expr::Call(paren_call(p, name)));
+                return Some(paren_call(p, name));
             } else {
                 return Some(Expr::Ident(ident));
             }
@@ -341,21 +342,21 @@ fn value(p: &mut Parser) -> Option<Expr> {
 }
 
 // Parse a template value: `[...]`.
-fn template(p: &mut Parser) -> Tree {
+fn template(p: &mut Parser) -> Expr {
     p.push_mode(TokenMode::Markup);
     p.start_group(Group::Bracket);
     let tree = tree(p);
     p.pop_mode();
     p.end_group();
-    tree
+    Expr::Template(tree)
 }
 
 /// Parse a parenthesized function call.
-fn paren_call(p: &mut Parser, name: Spanned<Ident>) -> ExprCall {
+fn paren_call(p: &mut Parser, name: Spanned<Ident>) -> Expr {
     p.start_group(Group::Paren);
     let args = p.span(arguments);
     p.end_group();
-    ExprCall { name, args }
+    Expr::Call(ExprCall { name, args })
 }
 
 /// Parse an identifier.
diff --git a/src/parse/tests.rs b/src/parse/tests.rs
index a8897c1c..b9a3d301 100644
--- a/src/parse/tests.rs
+++ b/src/parse/tests.rs
@@ -10,8 +10,8 @@ use crate::syntax::*;
 
 use BinOp::*;
 use Expr::{Angle, Bool, Color, Float, Int, Length, Percent};
-use Node::{Emph, Expr as Block, Linebreak, Parbreak, Space, Strong};
-use UnOp::*;
+use Node::{Emph, Linebreak, Parbreak, Space, Strong};
+use UnOp::{Neg, Pos};
 
 macro_rules! t {
     ($src:literal
@@ -126,21 +126,26 @@ fn Unary(op: impl Into<Spanned<UnOp>>, expr: impl Into<Spanned<Expr>>) -> Expr {
     })
 }
 
-macro_rules! Array {
-    (@$($expr:expr),* $(,)?) => {
-        vec![$(into!($expr)),*]
-    };
-    ($($tts:tt)*) => (Expr::Array(Array![@$($tts)*]));
+fn Group(expr: Expr) -> Expr {
+    Expr::Group(Box::new(expr))
 }
 
-macro_rules! Dict {
-    (@$($name:expr => $expr:expr),* $(,)?) => {
-        vec![$(Named {
+macro_rules! Call {
+    (@@$name:expr) => {
+        Call!(@@$name, Args![])
+    };
+    (@@$name:expr, $args:expr) => {
+        ExprCall {
             name: into!($name).map(|s: &str| Ident(s.into())),
-            expr: into!($expr)
-        }),*]
+            args: into!($args),
+        }
+    };
+    (@$($tts:tt)*) => {
+        Expr::Call(Call!(@@$($tts)*))
+    };
+    ($($tts:tt)*) => {
+        Node::Expr(Call!(@$($tts)*))
     };
-    ($($tts:tt)*) => (Expr::Dict(Dict![@$($tts)*]));
 }
 
 macro_rules! Args {
@@ -158,23 +163,43 @@ macro_rules! Args {
     };
 }
 
+macro_rules! Array {
+    (@$($expr:expr),* $(,)?) => {
+        vec![$(into!($expr)),*]
+    };
+    ($($tts:tt)*) => {
+        Expr::Array(Array![@$($tts)*])
+    };
+}
+
+macro_rules! Dict {
+    (@$($name:expr => $expr:expr),* $(,)?) => {
+        vec![$(Named {
+            name: into!($name).map(|s: &str| Ident(s.into())),
+            expr: into!($expr)
+        }),*]
+    };
+    ($($tts:tt)*) => {
+        Expr::Dict(Dict![@$($tts)*])
+    };
+}
+
 macro_rules! Template {
-    (@$($node:expr),* $(,)?) => (vec![$(into!($node)),*]);
-    ($($tts:tt)*) => (Expr::Template(Template![@$($tts)*]));
+    (@$($node:expr),* $(,)?) => {
+        vec![$(into!($node)),*]
+    };
+    ($($tts:tt)*) => {
+        Expr::Template(Template![@$($tts)*])
+    };
 }
 
-macro_rules! Call {
-    (@@$name:expr) => {
-        Call!(@@$name, Args![])
+macro_rules! Block {
+    (@$expr:expr) => {
+        Expr::Block(Box::new($expr))
     };
-    (@@$name:expr, $args:expr) => {
-        ExprCall {
-            name: into!($name).map(|s: &str| Ident(s.into())),
-            args: into!($args),
-        }
+    ($expr:expr) => {
+        Node::Expr(Block!(@$expr))
     };
-    (@$($tts:tt)*) => (Expr::Call(Call!(@@$($tts)*)));
-    ($($tts:tt)*) => (Node::Expr(Call!(@$($tts)*)));
 }
 
 #[test]
@@ -247,7 +272,7 @@ fn test_parse_headings() {
 
     // Continued heading.
     t!("# a{\n1\n}b"   Heading(0, Template![
-        @Space, Text("a"), Block(Int(1)), Text("b")
+        @Space, Text("a"), Block!(Int(1)), Text("b")
     ]));
     t!("# a[f][\n\n]d" Heading(0, Template![@
         Space, Text("a"), Call!("f", Args![Template![Parbreak]]), Text("d"),
@@ -294,7 +319,7 @@ fn test_parse_escape_sequences() {
 fn test_parse_groups() {
     // Test paren group.
     t!("{({1) + 3}"
-        nodes: [Block(Binary(Int(1), Add, Int(3)))],
+        nodes: [Block!(Binary(Group(Block!(@Int(1))), Add, Int(3)))],
         errors: [S(4..4, "expected closing brace")]);
 
     // Test bracket group.
@@ -309,7 +334,7 @@ fn test_parse_groups() {
 
     // Test brace group.
     t!("{1 + [}"
-        nodes: [Block(Binary(Int(1), Add, Template![]))],
+        nodes: [Block!(Binary(Int(1), Add, Template![]))],
         errors: [S(6..6, "expected closing bracket")]);
 
     // Test subheader group.
@@ -322,11 +347,11 @@ fn test_parse_groups() {
 #[test]
 fn test_parse_blocks() {
     // Basic with spans.
-    t!("{1}" nodes: [S(0..3, Block(Int(1)))], spans: true);
+    t!("{1}" nodes: [S(0..3, Block!(Int(1)))], spans: true);
 
     // Function calls.
-    t!("{f()}" Call!("f"));
-    t!("{[[f]]}" Block(Template![Call!("f")]));
+    t!("{f()}" Block!(Call!(@"f")));
+    t!("{[[f]]}" Block!(Template![Call!("f")]));
 
     // Missing or bad value.
     t!("{}{1u}"
@@ -336,7 +361,7 @@ fn test_parse_blocks() {
 
     // Too much stuff.
     t!("{1 #{} end"
-        nodes: [Block(Int(1)), Space, Text("end")],
+        nodes: [Block!(Int(1)), Space, Text("end")],
         errors: [S(3..4, "unexpected hex value"),
                  S(4..5, "unexpected opening brace")]);
 }
@@ -424,7 +449,7 @@ fn test_parse_arguments() {
     t!("[v a:2]" Call!("v", Args!["a" => Int(2)]));
 
     // Parenthesized function with nested array literal.
-    t!(r#"{f(1, a: (2, 3), #004, b: "five")}"# Block(Call!(@"f", Args![
+    t!(r#"{f(1, a: (2, 3), #004, b: "five")}"# Block!(Call!(@"f", Args![
         Int(1),
         "a" => Array![Int(2), Int(3)],
         Color(RgbaColor::new(0, 0, 0x44, 0xff)),
@@ -449,30 +474,35 @@ fn test_parse_arguments() {
     // Name has to be identifier.
     t!("[v 1:]"
         nodes: [Call!("v", Args![])],
-        errors: [S(3..4, "name must be identifier"),
+        errors: [S(3..4, "expected identifier"),
                  S(5..5, "expected expression")]);
 
     // Name has to be identifier.
     t!("[v 1:2]"
         nodes: [Call!("v", Args![])],
-        errors: [S(3..4, "name must be identifier")]);
+        errors: [S(3..4, "expected identifier")]);
+
+    // Name has to be identifier.
+    t!("[v (x):1]"
+        nodes: [Call!("v", Args![])],
+        errors: [S(3..6, "expected identifier")]);
 }
 
 #[test]
 fn test_parse_arrays() {
     // Empty array.
-    t!("{()}" Block(Array![]));
+    t!("{()}" Block!(Array![]));
 
     // Array with one item and trailing comma + spans.
     t!("{-(1,)}"
-        nodes: [S(0..7, Block(Unary(
+        nodes: [S(0..7, Block!(Unary(
             S(1..2, Neg),
             S(2..6, Array![S(3..4, Int(1))])
         )))],
         spans: true);
 
     // Array with three items and trailing comma.
-    t!(r#"{("one", 2, #003,)}"# Block(Array![
+    t!(r#"{("one", 2, #003,)}"# Block!(Array![
         Str("one"),
         Int(2),
         Color(RgbaColor::new(0, 0, 0x33, 0xff))
@@ -480,44 +510,44 @@ fn test_parse_arrays() {
 
     // Unclosed.
     t!("{(}"
-        nodes: [Block(Array![])],
+        nodes: [Block!(Array![])],
         errors: [S(2..2, "expected closing paren")]);
 
     // Missing comma + invalid token.
     t!("{(1*/2)}"
-        nodes: [Block(Array![Int(1), Int(2)])],
+        nodes: [Block!(Array![Int(1), Int(2)])],
         errors: [S(3..5, "expected expression, found end of block comment"),
                  S(3..3, "expected comma")]);
 
     // Invalid token.
     t!("{(1, 1u 2)}"
-        nodes: [Block(Array![Int(1), Int(2)])],
+        nodes: [Block!(Array![Int(1), Int(2)])],
         errors: [S(5..7, "expected expression, found invalid token")]);
 
     // Coerced to expression with leading comma.
     t!("{(,1)}"
-        nodes: [Block(Int(1))],
+        nodes: [Block!(Group(Int(1)))],
         errors: [S(2..3, "expected expression, found comma")]);
 
     // Missing expression after name makes this an array.
     t!("{(a:)}"
-        nodes: [Block(Array![])],
+        nodes: [Block!(Array![])],
         errors: [S(4..4, "expected expression")]);
 
     // Expected expression, found named pair.
     t!("{(1, b: 2)}"
-        nodes: [Block(Array![Int(1)])],
+        nodes: [Block!(Array![Int(1)])],
         errors: [S(5..9, "expected expression, found named pair")]);
 }
 
 #[test]
 fn test_parse_dictionaries() {
     // Empty dictionary.
-    t!("{(:)}" Block(Dict![]));
+    t!("{(:)}" Block!(Dict![]));
 
     // Dictionary with two pairs + spans.
     t!("{(one: 1, two: 2)}"
-        nodes: [S(0..18, Block(Dict![
+        nodes: [S(0..18, Block!(Dict![
             S(2..5, "one") => S(7..8, Int(1)),
             S(10..13, "two") => S(15..16, Int(2)),
         ]))],
@@ -525,49 +555,50 @@ fn test_parse_dictionaries() {
 
     // Expected named pair, found expression.
     t!("{(a: 1, b)}"
-        nodes: [Block(Dict!["a" => Int(1)])],
+        nodes: [Block!(Dict!["a" => Int(1)])],
         errors: [S(8..9, "expected named pair, found expression")]);
 
     // Dictionary marker followed by more stuff.
     t!("{(:1 b:[], true::)}"
-        nodes: [Block(Dict!["b" => Template![]])],
+        nodes: [Block!(Dict!["b" => Template![]])],
         errors: [S(3..4, "expected named pair, found expression"),
                  S(4..4, "expected comma"),
-                 S(11..15, "name must be identifier"),
+                 S(11..15, "expected identifier"),
                  S(16..17, "expected expression, found colon")]);
 }
 
 #[test]
 fn test_parse_expressions() {
     // Parentheses.
-    t!("{(x)}{(1)}" Block(Id("x")), Block(Int(1)));
+    t!("{(x)}{(1)}" Block!(Group(Id("x"))), Block!(Group(Int(1))));
 
     // Unary operations.
-    t!("{-1}"  Block(Unary(Neg, Int(1))));
-    t!("{--1}" Block(Unary(Neg, Unary(Neg, Int(1)))));
+    t!("{+1}"  Block!(Unary(Pos, Int(1))));
+    t!("{-1}"  Block!(Unary(Neg, Int(1))));
+    t!("{--1}" Block!(Unary(Neg, Unary(Neg, Int(1)))));
 
     // Binary operations.
-    t!(r#"{"x"+"y"}"# Block(Binary(Str("x"), Add, Str("y"))));
-    t!("{1-2}"        Block(Binary(Int(1), Sub, Int(2))));
-    t!("{a * b}"      Block(Binary(Id("a"), Mul, Id("b"))));
-    t!("{12pt/.4}"    Block(Binary(Length(12.0, LengthUnit::Pt), Div, Float(0.4))));
+    t!(r#"{"x"+"y"}"# Block!(Binary(Str("x"), Add, Str("y"))));
+    t!("{1-2}"        Block!(Binary(Int(1), Sub, Int(2))));
+    t!("{a * b}"      Block!(Binary(Id("a"), Mul, Id("b"))));
+    t!("{12pt/.4}"    Block!(Binary(Length(12.0, LengthUnit::Pt), Div, Float(0.4))));
 
     // Associativity.
-    t!("{1+2+3}" Block(Binary(Binary(Int(1), Add, Int(2)), Add, Int(3))));
-    t!("{1/2*3}" Block(Binary(Binary(Int(1), Div, Int(2)), Mul, Int(3))));
+    t!("{1+2+3}" Block!(Binary(Binary(Int(1), Add, Int(2)), Add, Int(3))));
+    t!("{1/2*3}" Block!(Binary(Binary(Int(1), Div, Int(2)), Mul, Int(3))));
 
     // Precedence.
-    t!("{1+2*-3}" Block(Binary(
+    t!("{1+2*-3}" Block!(Binary(
         Int(1), Add, Binary(Int(2), Mul, Unary(Neg, Int(3))),
     )));
 
     // Confusion with floating-point literal.
-    t!("{1e-3-4e+4}" Block(Binary(Float(1e-3), Sub, Float(4e+4))));
+    t!("{1e-3-4e+4}" Block!(Binary(Float(1e-3), Sub, Float(4e+4))));
 
     // Spans + parentheses winning over precedence.
     t!("{(1+2)*3}"
-        nodes: [S(0..9, Block(Binary(
-            S(1..6, Binary(S(2..3, Int(1)), S(3..4, Add), S(4..5, Int(2)))),
+        nodes: [S(0..9, Block!(Binary(
+            S(1..6, Group(Binary(S(2..3, Int(1)), S(3..4, Add), S(4..5, Int(2))))),
             S(6..7, Mul),
             S(7..8, Int(3)),
         )))],
@@ -575,7 +606,7 @@ fn test_parse_expressions() {
 
     // Errors.
     t!("{-}{1+}{2*}"
-        nodes: [Block(Int(1)), Block(Int(2))],
+        nodes: [Block!(Int(1)), Block!(Int(2))],
         errors: [S(2..2, "expected expression"),
                  S(6..6, "expected expression"),
                  S(10..10, "expected expression")]);
@@ -584,37 +615,36 @@ fn test_parse_expressions() {
 #[test]
 fn test_parse_values() {
     // Basics.
-    t!("{_}"      Block(Id("_")));
-    t!("{name}"   Block(Id("name")));
-    t!("{ke-bab}" Block(Id("ke-bab")));
-    t!("{α}"      Block(Id("α")));
-    t!("{none}"   Block(Expr::None));
-    t!("{true}"   Block(Bool(true)));
-    t!("{false}"  Block(Bool(false)));
-    t!("{1.0e-4}" Block(Float(1e-4)));
-    t!("{3.15}"   Block(Float(3.15)));
-    t!("{50%}"    Block(Percent(50.0)));
-    t!("{4.5cm}"  Block(Length(4.5, LengthUnit::Cm)));
-    t!("{12e1pt}" Block(Length(12e1, LengthUnit::Pt)));
-    t!("{13rad}"  Block(Angle(13.0, AngularUnit::Rad)));
-    t!("{45deg}"  Block(Angle(45.0, AngularUnit::Deg)));
+    t!("{_}"      Block!(Id("_")));
+    t!("{name}"   Block!(Id("name")));
+    t!("{ke-bab}" Block!(Id("ke-bab")));
+    t!("{α}"      Block!(Id("α")));
+    t!("{none}"   Block!(Expr::None));
+    t!("{true}"   Block!(Bool(true)));
+    t!("{false}"  Block!(Bool(false)));
+    t!("{1.0e-4}" Block!(Float(1e-4)));
+    t!("{3.15}"   Block!(Float(3.15)));
+    t!("{50%}"    Block!(Percent(50.0)));
+    t!("{4.5cm}"  Block!(Length(4.5, LengthUnit::Cm)));
+    t!("{12e1pt}" Block!(Length(12e1, LengthUnit::Pt)));
+    t!("{13rad}"  Block!(Angle(13.0, AngularUnit::Rad)));
+    t!("{45deg}"  Block!(Angle(45.0, AngularUnit::Deg)));
 
     // Strings.
-    t!(r#"{"hi"}"#                     Block(Str("hi")));
-    t!(r#"{"a\n[]\"\u{1F680}string"}"# Block(Str("a\n[]\"🚀string")));
+    t!(r#"{"hi"}"#                     Block!(Str("hi")));
+    t!(r#"{"a\n[]\"\u{1F680}string"}"# Block!(Str("a\n[]\"🚀string")));
 
     // Colors.
-    t!("{#f7a20500}" Block(Color(RgbaColor::new(0xf7, 0xa2, 0x05, 0))));
+    t!("{#f7a20500}" Block!(Color(RgbaColor::new(0xf7, 0xa2, 0x05, 0))));
     t!("{#a5}"
-        nodes: [Block(Color(RgbaColor::new(0, 0, 0, 0xff)))],
+        nodes: [Block!(Color(RgbaColor::new(0, 0, 0, 0xff)))],
         errors: [S(1..4, "invalid color")]);
 
     // Content.
-    t!("{[*Hi*]}" Block(Template![Strong, Text("Hi"), Strong]));
+    t!("{[*Hi*]}" Block!(Template![Strong, Text("Hi"), Strong]));
 
     // Nested blocks.
-    t!("{{1}}" Block(Int(1)));
-    t!("{{{1+2}}}" Block(Binary(Int(1), Add, Int(2))));
+    t!("{{1}}" Block!(Block!(@Int(1))));
 
     // Invalid tokens.
     t!("{1u}"
diff --git a/src/syntax/expr.rs b/src/syntax/expr.rs
index cb09041c..09472df4 100644
--- a/src/syntax/expr.rs
+++ b/src/syntax/expr.rs
@@ -40,6 +40,10 @@ pub enum Expr {
     Dict(ExprDict),
     /// A template expression: `[*Hi* there!]`.
     Template(ExprTemplate),
+    /// A grouped expression: `(1 + 2)`.
+    Group(Box<Expr>),
+    /// A block expression: `{1 + 2}`.
+    Block(Box<Expr>),
 }
 
 impl Pretty for Expr {
@@ -54,24 +58,31 @@ impl Pretty for Expr {
             Self::Angle(v, u) => write!(p, "{}{}", v, u).unwrap(),
             Self::Percent(v) => write!(p, "{}%", v).unwrap(),
             Self::Color(v) => write!(p, "{}", v).unwrap(),
-            Self::Str(s) => write!(p, "{:?}", &s).unwrap(),
-            Self::Call(call) => call.pretty(p),
-            Self::Unary(unary) => unary.pretty(p),
-            Self::Binary(binary) => binary.pretty(p),
-            Self::Array(array) => array.pretty(p),
-            Self::Dict(dict) => dict.pretty(p),
-            Self::Template(template) => pretty_template_expr(template, p),
+            Self::Str(v) => write!(p, "{:?}", &v).unwrap(),
+            Self::Call(v) => v.pretty(p),
+            Self::Unary(v) => v.pretty(p),
+            Self::Binary(v) => v.pretty(p),
+            Self::Array(v) => v.pretty(p),
+            Self::Dict(v) => v.pretty(p),
+            Self::Template(v) => {
+                p.push_str("[");
+                v.pretty(p);
+                p.push_str("]");
+            }
+            Self::Group(v) => {
+                p.push_str("(");
+                v.pretty(p);
+                p.push_str(")");
+            }
+            Self::Block(v) => {
+                p.push_str("{");
+                v.pretty(p);
+                p.push_str("}");
+            }
         }
     }
 }
 
-/// Pretty print a template in an expression context.
-pub fn pretty_template_expr(tree: &Tree, p: &mut Printer) {
-    p.push_str("[");
-    tree.pretty(p);
-    p.push_str("]");
-}
-
 /// An invocation of a function: `[foo ...]`, `foo(...)`.
 #[derive(Debug, Clone, PartialEq)]
 pub struct ExprCall {
@@ -197,6 +208,8 @@ impl Pretty for ExprUnary {
 /// A unary operator.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub enum UnOp {
+    /// The plus operator: `+`.
+    Pos,
     /// The negation operator: `-`.
     Neg,
 }
@@ -204,6 +217,7 @@ pub enum UnOp {
 impl Pretty for UnOp {
     fn pretty(&self, p: &mut Printer) {
         p.push_str(match self {
+            Self::Pos => "+",
             Self::Neg => "-",
         });
     }
@@ -302,7 +316,11 @@ mod tests {
     fn test_pretty_print_expressions() {
         // Unary and binary operations.
         test_pretty("{1 +}", "{1}");
+        test_pretty("{1++1}", "{1 + +1}");
+        test_pretty("{+-1}", "{+-1}");
         test_pretty("{1 + func(-2)}", "{1 + func(-2)}");
+        test_pretty("{1+2*3}", "{1 + 2 * 3}");
+        test_pretty("{(1+2)*3}", "{(1 + 2) * 3}");
 
         // Array.
         test_pretty("(-5,)", "(-5,)");
@@ -314,6 +332,10 @@ mod tests {
 
         // Content expression.
         test_pretty("[v [[f]], 1]", "[v [[f]], 1]");
+
+        // Parens and blocks.
+        test_pretty("{(1)}", "{(1)}");
+        test_pretty("{{1}}", "{{1}}");
     }
 
     #[test]
diff --git a/src/syntax/node.rs b/src/syntax/node.rs
index e7091a40..5c4c22b7 100644
--- a/src/syntax/node.rs
+++ b/src/syntax/node.rs
@@ -34,29 +34,14 @@ impl Pretty for Node {
             Self::Text(text) => p.push_str(&text),
             Self::Heading(heading) => heading.pretty(p),
             Self::Raw(raw) => raw.pretty(p),
-            Self::Expr(expr) => pretty_expr_node(expr, p),
-        }
-    }
-}
-
-/// Pretty print an expression in a node context.
-pub fn pretty_expr_node(expr: &Expr, p: &mut Printer) {
-    match expr {
-        // Prefer bracket calls over expression blocks with just a single paren
-        // call.
-        //
-        // Example: Transforms "{v()}" => "[v]".
-        Expr::Call(call) => pretty_bracket_call(call, p, false),
-
-        // Remove unncessary nesting of content and expression blocks.
-        //
-        // Example: Transforms "{[Hi]}" => "Hi".
-        Expr::Template(template) => template.pretty(p),
-
-        _ => {
-            p.push_str("{");
-            expr.pretty(p);
-            p.push_str("}");
+            Self::Expr(expr) => {
+                if let Expr::Call(call) = expr {
+                    // Format bracket calls appropriately.
+                    pretty_bracket_call(call, p, false)
+                } else {
+                    expr.pretty(p);
+                }
+            }
         }
     }
 }
@@ -178,18 +163,13 @@ mod tests {
     use super::super::tests::test_pretty;
 
     #[test]
-    fn test_pretty_print_removes_nesting() {
-        // Nesting does not matter.
-        test_pretty("{{x}}", "{x}");
-        test_pretty("{{{x}}}", "{x}");
-    }
-
-    #[test]
-    fn test_pretty_print_prefers_bracket_calls() {
-        // All reduces to a simple bracket call.
-        test_pretty("{v()}", "[v]");
+    fn test_pretty_print_bracket_calls() {
+        // Top-level call expression formatted as bracket call.
         test_pretty("[v]", "[v]");
-        test_pretty("{[[v]]}", "[v]");
+
+        // Blocks are preserved.
+        test_pretty("{v()}", "{v()}");
+        test_pretty("{[[v]]}", "{[[v]]}");
     }
 
     #[test]