Refactor expressions and create tuples and objects 🧮

5 files changed, 201 insertions, 151 deletions

diff --git a/src/syntax/color.rs b/src/syntax/color.rs
index 716cb688..7f34fad7 100644
--- a/src/syntax/color.rs
+++ b/src/syntax/color.rs
@@ -15,7 +15,7 @@ pub enum ColorToken {
     Brace,
 
     ExprIdent,
-    ExprString,
+    ExprStr,
     ExprNumber,
     ExprSize,
     ExprBool,
diff --git a/src/syntax/expr.rs b/src/syntax/expr.rs
index ed5e50df..e2df3c4e 100644
--- a/src/syntax/expr.rs
+++ b/src/syntax/expr.rs
@@ -1,125 +1,16 @@
 use super::*;
 
 
-/// The arguments passed to a function.
-#[derive(Debug, Clone, PartialEq)]
-pub struct FuncArgs {
-    pub pos: Vec<Spanned<PosArg>>,
-    pub key: Vec<Spanned<KeyArg>>,
-}
-
-impl FuncArgs {
-    /// Create an empty collection of arguments.
-    pub fn new() -> FuncArgs {
-        FuncArgs {
-            pos: vec![],
-            key: vec![],
-        }
-    }
-
-    /// Add a positional argument.
-    pub fn add_pos(&mut self, arg: Spanned<PosArg>) {
-        self.pos.push(arg);
-    }
-
-    /// Add a keyword argument.
-    pub fn add_key(&mut self, arg: Spanned<KeyArg>) {
-        self.key.push(arg);
-    }
-
-    /// Force-extract the first positional argument.
-    pub fn get_pos<E: ExpressionKind>(&mut self) -> ParseResult<E> {
-        expect(self.get_pos_opt())
-    }
-
-    /// Extract the first positional argument.
-    pub fn get_pos_opt<E: ExpressionKind>(&mut self) -> ParseResult<Option<E>> {
-        Ok(if !self.pos.is_empty() {
-            let spanned = self.pos.remove(0);
-            Some(E::from_expr(spanned)?)
-        } else {
-            None
-        })
-    }
-
-    /// Iterator over positional arguments.
-    pub fn pos(&mut self) -> std::vec::IntoIter<Spanned<PosArg>> {
-        let vec = std::mem::replace(&mut self.pos, vec![]);
-        vec.into_iter()
-    }
-
-    /// Force-extract a keyword argument.
-    pub fn get_key<E: ExpressionKind>(&mut self, name: &str) -> ParseResult<E> {
-        expect(self.get_key_opt(name))
-    }
-
-    /// Extract a keyword argument.
-    pub fn get_key_opt<E: ExpressionKind>(&mut self, name: &str) -> ParseResult<Option<E>> {
-        Ok(if let Some(index) = self.key.iter().position(|arg| arg.v.key.v.0 == name) {
-            let value = self.key.swap_remove(index).v.value;
-            Some(E::from_expr(value)?)
-        } else {
-            None
-        })
-    }
-
-    /// Extract any keyword argument.
-    pub fn get_key_next(&mut self) -> Option<Spanned<KeyArg>> {
-        self.key.pop()
-    }
-
-    /// Iterator over all keyword arguments.
-    pub fn keys(&mut self) -> std::vec::IntoIter<Spanned<KeyArg>> {
-        let vec = std::mem::replace(&mut self.key, vec![]);
-        vec.into_iter()
-    }
-
-    /// Clear the argument lists.
-    pub fn clear(&mut self) {
-        self.pos.clear();
-        self.key.clear();
-    }
-
-    /// Whether both the positional and keyword argument lists are empty.
-    pub fn is_empty(&self) -> bool {
-        self.pos.is_empty() && self.key.is_empty()
-    }
-}
-
-/// Extract the option expression kind from the option or return an error.
-fn expect<E: ExpressionKind>(opt: ParseResult<Option<E>>) -> ParseResult<E> {
-    match opt {
-        Ok(Some(spanned)) => Ok(spanned),
-        Ok(None) => error!("expected {}", E::NAME),
-        Err(e) => Err(e),
-    }
-}
-
-/// A positional argument passed to a function.
-pub type PosArg = Expression;
-
-/// A keyword argument passed to a function.
-#[derive(Debug, Clone, PartialEq)]
-pub struct KeyArg {
-    pub key: Spanned<Ident>,
-    pub value: Spanned<Expression>,
-}
-
-/// Either a positional or keyword argument.
-#[derive(Debug, Clone, PartialEq)]
-pub enum DynArg {
-    Pos(Spanned<PosArg>),
-    Key(Spanned<KeyArg>),
-}
-
 /// An argument or return value.
 #[derive(Clone, PartialEq)]
 pub enum Expression {
     Ident(Ident),
     Str(String),
-    Num(f64),
+    Number(f64),
     Size(Size),
     Bool(bool),
+    Tuple(Tuple),
+    Object(Object),
 }
 
 impl Display for Expression {
@@ -128,20 +19,17 @@ impl Display for Expression {
         match self {
             Ident(i) => write!(f, "{}", i),
             Str(s) => write!(f, "{:?}", s),
-            Num(n) => write!(f, "{}", n),
+            Number(n) => write!(f, "{}", n),
             Size(s) => write!(f, "{}", s),
             Bool(b) => write!(f, "{}", b),
+            Tuple(t) => write!(f, "{}", t),
+            Object(o) => write!(f, "{}", o),
         }
     }
 }
 
-debug_display!(Expression);
-
-pub struct Tuple;
-pub struct Object;
-
 /// An identifier.
-#[derive(Clone, PartialEq)]
+#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
 pub struct Ident(pub String);
 
 impl Ident {
@@ -164,16 +52,98 @@ impl Display for Ident {
     }
 }
 
+/// A sequence of expressions.
+#[derive(Clone, PartialEq)]
+pub struct Tuple {
+    pub items: Vec<Spanned<Expression>>,
+}
+
+impl Tuple {
+    pub fn new() -> Tuple {
+        Tuple { items: vec![] }
+    }
+
+    pub fn add(&mut self, item: Spanned<Expression>) {
+        self.items.push(item);
+    }
+}
+
+impl Display for Tuple {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "(")?;
+
+        let mut first = true;
+        for item in &self.items {
+            if !first {
+                write!(f, ", ")?;
+            }
+            write!(f, "{}", item.v)?;
+            first = false;
+        }
+
+        write!(f, ")")
+    }
+}
+
+/// A key-value collection of identifiers and associated expressions.
+#[derive(Clone, PartialEq)]
+pub struct Object {
+    pub pairs: Vec<Pair>,
+}
+
+#[derive(Clone, PartialEq)]
+pub struct Pair {
+    pub key: Spanned<Ident>,
+    pub value: Spanned<Expression>,
+}
+
+impl Object {
+    pub fn new() -> Object {
+        Object { pairs: vec![] }
+    }
+
+    pub fn add(&mut self, key: Spanned<Ident>, value: Spanned<Expression>) {
+        self.pairs.push(Pair { key, value });
+    }
+
+    pub fn add_pair(&mut self, pair: Pair) {
+        self.pairs.push(pair);
+    }
+}
+
+impl Display for Object {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "{{ ")?;
+
+        let mut first = true;
+        for pair in &self.pairs {
+            if !first {
+                write!(f, ", ")?;
+            }
+            write!(f, "{}: {}", pair.key.v, pair.value.v)?;
+            first = false;
+        }
+
+        write!(f, " }}")
+    }
+}
+
 debug_display!(Ident);
+debug_display!(Expression);
+debug_display!(Tuple);
+debug_display!(Object);
+
 
 /// Kinds of expressions.
 pub trait ExpressionKind: Sized {
+    /// The name of the expression in an `expected <name>` error.
     const NAME: &'static str;
 
     /// Create from expression.
     fn from_expr(expr: Spanned<Expression>) -> ParseResult<Self>;
 }
 
+/// Implements the expression kind trait for a type.
 macro_rules! kind {
     ($type:ty, $name:expr, $($patterns:tt)*) => {
         impl ExpressionKind for $type {
@@ -190,15 +160,18 @@ macro_rules! kind {
     };
 }
 
-kind!(Expression, "expression", e                         => e);
-kind!(Ident,      "identifier", Expression::Ident(ident)  => ident);
-kind!(String,     "string",     Expression::Str(string)   => string);
-kind!(f64,        "number",     Expression::Num(num)      => num);
-kind!(bool,       "boolean",    Expression::Bool(boolean) => boolean);
-kind!(Size,       "size",       Expression::Size(size)    => size);
+kind!(Expression, "expression", e                          => e);
+kind!(Ident,      "identifier", Expression::Ident(ident)   => ident);
+kind!(String,     "string",     Expression::Str(string)    => string);
+kind!(f64,        "number",     Expression::Number(num)    => num);
+kind!(bool,       "boolean",    Expression::Bool(boolean)  => boolean);
+kind!(Size,       "size",       Expression::Size(size)     => size);
+kind!(Tuple,      "tuple",      Expression::Tuple(tuple)   => tuple);
+kind!(Object,     "object",     Expression::Object(object) => object);
+
 kind!(ScaleSize,  "number or size",
-    Expression::Size(size) => ScaleSize::Absolute(size),
-    Expression::Num(scale) => ScaleSize::Scaled(scale as f32)
+    Expression::Size(size)    => ScaleSize::Absolute(size),
+    Expression::Number(scale) => ScaleSize::Scaled(scale as f32)
 );
 
 impl<T> ExpressionKind for Spanned<T> where T: ExpressionKind {
@@ -206,22 +179,6 @@ impl<T> ExpressionKind for Spanned<T> where T: ExpressionKind {
 
     fn from_expr(expr: Spanned<Expression>) -> ParseResult<Spanned<T>> {
         let span = expr.span;
-        T::from_expr(expr)
-            .map(|v| Spanned::new(v, span))
-    }
-}
-
-impl<T> ExpressionKind for Option<T> where T: ExpressionKind {
-    const NAME: &'static str = T::NAME;
-
-    fn from_expr(expr: Spanned<Expression>) -> ParseResult<Option<T>> {
-        if let Expression::Ident(ident) = &expr.v {
-            match ident.as_str() {
-                "default" | "none" => return Ok(None),
-                _ => {},
-            }
-        }
-
-        T::from_expr(expr).map(|v| Some(v))
+        T::from_expr(expr).map(|v| Spanned { v, span })
     }
 }
diff --git a/src/syntax/parsing.rs b/src/syntax/parsing.rs
index 112c2f65..47322485 100644
--- a/src/syntax/parsing.rs
+++ b/src/syntax/parsing.rs
@@ -47,6 +47,99 @@ impl PartialEq for FuncCall {
     }
 }
 
+#[derive(Debug)]
+pub struct FuncArgs {
+    positional: Tuple,
+    keyword: Object,
+}
+
+impl FuncArgs {
+    fn new() -> FuncArgs {
+        FuncArgs {
+            positional: Tuple::new(),
+            keyword: Object::new(),
+        }
+    }
+
+    /// Add a positional argument.
+    pub fn add_pos(&mut self, item: Spanned<Expression>) {
+        self.positional.add(item);
+    }
+
+    /// Force-extract the first positional argument.
+    pub fn get_pos<E: ExpressionKind>(&mut self) -> ParseResult<E> {
+        expect(self.get_pos_opt())
+    }
+
+    /// Extract the first positional argument.
+    pub fn get_pos_opt<E: ExpressionKind>(&mut self) -> ParseResult<Option<E>> {
+        Ok(if !self.positional.items.is_empty() {
+            let spanned = self.positional.items.remove(0);
+            Some(E::from_expr(spanned)?)
+        } else {
+            None
+        })
+    }
+
+    /// Add a keyword argument.
+    pub fn add_key(&mut self, key: Spanned<Ident>, value: Spanned<Expression>) {
+        self.keyword.add(key, value);
+    }
+
+    /// Add a keyword argument from an existing pair.
+    pub fn add_key_pair(&mut self, pair: Pair) {
+        self.keyword.add_pair(pair);
+    }
+
+    /// Force-extract a keyword argument.
+    pub fn get_key<E: ExpressionKind>(&mut self, name: &str) -> ParseResult<E> {
+        expect(self.get_key_opt(name))
+    }
+
+    /// Extract a keyword argument.
+    pub fn get_key_opt<E: ExpressionKind>(&mut self, name: &str) -> ParseResult<Option<E>> {
+        self.keyword.pairs.iter()
+            .position(|p| p.key.v.0 == name)
+            .map(|index| {
+                let value = self.keyword.pairs.swap_remove(index).value;
+                E::from_expr(value)
+            })
+            .transpose()
+    }
+
+    /// Iterator over positional arguments.
+    pub fn iter_pos(&mut self) -> std::vec::IntoIter<Spanned<Expression>> {
+        let tuple = std::mem::replace(&mut self.positional, Tuple::new());
+        tuple.items.into_iter()
+    }
+
+    /// Iterator over all keyword arguments.
+    pub fn iter_keys(&mut self) -> std::vec::IntoIter<Pair> {
+        let object = std::mem::replace(&mut self.keyword, Object::new());
+        object.pairs.into_iter()
+    }
+
+    /// Clear the argument lists.
+    pub fn clear(&mut self) {
+        self.positional.items.clear();
+        self.keyword.pairs.clear();
+    }
+
+    /// Whether both the positional and keyword argument lists are empty.
+    pub fn is_empty(&self) -> bool {
+        self.positional.items.is_empty() && self.keyword.pairs.is_empty()
+    }
+}
+
+/// Extract the option expression kind from the option or return an error.
+fn expect<E: ExpressionKind>(opt: ParseResult<Option<E>>) -> ParseResult<E> {
+    match opt {
+        Ok(Some(spanned)) => Ok(spanned),
+        Ok(None) => error!("expected {}", E::NAME),
+        Err(e) => Err(e),
+    }
+}
+
 /// Parses source code into a syntax tree given a context.
 pub fn parse(src: &str, ctx: ParseContext) -> SyntaxTree {
     Parser::new(src, ctx).parse()
@@ -346,7 +439,7 @@ impl<'s> Parser<'s> {
             Comma  => Some(ColorToken::Comma),
             Equals => Some(ColorToken::Equals),
             ExprIdent(_)  =>  Some(ColorToken::ExprIdent),
-            ExprString(_) => Some(ColorToken::ExprString),
+            ExprStr(_) => Some(ColorToken::ExprStr),
             ExprNumber(_) => Some(ColorToken::ExprNumber),
             ExprSize(_)   => Some(ColorToken::ExprSize),
             ExprBool(_)   => Some(ColorToken::ExprBool),
@@ -387,7 +480,7 @@ fn name(token: Token) -> &'static str {
         Comma => "comma",
         Equals => "equals sign",
         ExprIdent(_) => "identifier",
-        ExprString(_) => "string",
+        ExprStr(_) => "string",
         ExprNumber(_) => "number",
         ExprSize(_) => "size",
         ExprBool(_) => "bool",
diff --git a/src/syntax/span.rs b/src/syntax/span.rs
index 10188ed4..e5c6912b 100644
--- a/src/syntax/span.rs
+++ b/src/syntax/span.rs
@@ -4,7 +4,7 @@ use std::fmt::{self, Display, Formatter};
 
 
 /// Annotates a value with the part of the source code it corresponds to.
-#[derive(Copy, Clone, Eq, PartialEq)]
+#[derive(Copy, Clone, Eq, PartialEq, Hash)]
 pub struct Spanned<T> {
     pub v: T,
     pub span: Span,
@@ -37,7 +37,7 @@ impl<T> Display for Spanned<T> where T: std::fmt::Debug {
 debug_display!(Spanned; T where T: std::fmt::Debug);
 
 /// Describes a slice of source code.
-#[derive(Copy, Clone, Eq, PartialEq)]
+#[derive(Copy, Clone, Eq, PartialEq, Hash)]
 pub struct Span {
     pub start: Position,
     pub end: Position,
diff --git a/src/syntax/tokens.rs b/src/syntax/tokens.rs
index ae5cfe48..295a4382 100644
--- a/src/syntax/tokens.rs
+++ b/src/syntax/tokens.rs
@@ -45,7 +45,7 @@ pub enum Token<'s> {
     /// An identifier in a function header: `center`.
     ExprIdent(&'s str),
     /// A quoted string in a function header: `"..."`.
-    ExprString(&'s str),
+    ExprStr(&'s str),
     /// A number in a function header: `3.14`.
     ExprNumber(f64),
     /// A size in a function header: `12pt`.
@@ -220,7 +220,7 @@ impl<'s> Tokens<'s> {
 
     fn parse_string(&mut self) -> Token<'s> {
         let mut escaped = false;
-        ExprString(self.read_string_until(|n| {
+        ExprStr(self.read_string_until(|n| {
             if n == '"' && !escaped {
                 return true;
             } else if n == '\\' {