Value operations can fail

src/builtin/macros.rs

@@ -1,18 +1,18 @@
 macro_rules! arg {
     ($args:ident, $idx:literal, $name:literal) => {
         match $args.remove(stringify!($idx)) {
-            Some(v) => v.eval(),
+            Some(v) => v.eval()?,
             None => match $args.remove($name) {
-                Some(v) => v.eval(),
+                Some(v) => v.eval()?,
                 None => return Err(concat!("Missing argument $", $name, ".").into()),
             },
         };
     };
     ($args:ident, $idx:literal, $name:literal=$default:expr) => {
         match $args.remove(stringify!($idx)) {
-            Some(v) => v.eval(),
+            Some(v) => v.eval()?,
             None => match $args.remove($name) {
-                Some(v) => v.eval(),
+                Some(v) => v.eval()?,
                 None => $default,
             },
         };

src/builtin/meta.rs

@@ -8,7 +8,7 @@ use crate::value::Value;
 pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
     decl!(f "if", |args, _| {
         max_args!(args, 3);
-        if arg!(args, 0, "condition").is_true() {
+        if arg!(args, 0, "condition").is_true()? {
             Ok(arg!(args, 1, "if-true"))
         } else {
             Ok(arg!(args, 2, "if-false"))
@@ -46,7 +46,7 @@ pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
     decl!(f "type-of", |args, _| {
         max_args!(args, 1);
         let value = arg!(args, 0, "value");
-        Ok(Value::Ident(value.kind().to_owned(), QuoteKind::None))
+        Ok(Value::Ident(value.kind()?.to_owned(), QuoteKind::None))
     });
     decl!(f "unitless", |args, _| {
         max_args!(args, 1);

src/value/mod.rs

@@ -4,6 +4,7 @@ use std::iter::Iterator;
 
 use crate::color::Color;
 use crate::common::{ListSeparator, Op, QuoteKind};
+use crate::error::SassResult;
 use crate::units::Unit;
 pub(crate) use number::Number;
 
@@ -39,7 +40,7 @@ impl Display for Value {
                     .join(sep.as_str())
             ),
             Self::Color(c) => write!(f, "{}", c),
-            Self::BinaryOp(..) => write!(f, "{}", self.clone().eval()),
+            Self::BinaryOp(..) => write!(f, "{}", self.clone().eval().unwrap()),
             Self::Paren(val) => write!(f, "{}", val),
             Self::Ident(val, kind) => write!(f, "{}{}{}", kind.as_str(), val, kind.as_str()),
             Self::True => write!(f, "true"),
@@ -54,11 +55,11 @@ impl Value {
         self == &Value::Null
     }
 
-    pub fn is_true(&self) -> bool {
+    pub fn is_true(&self) -> SassResult<bool> {
         match self {
-            Value::Null | Value::False => false,
+            Value::Null | Value::False => Ok(false),
-            Self::BinaryOp(..) => self.clone().eval().is_true(),
+            Self::BinaryOp(..) => self.clone().eval()?.is_true(),
-            _ => true,
+            _ => Ok(true),
         }
     }
 
@@ -69,17 +70,17 @@ impl Value {
         }
     }
 
-    pub fn kind(&self) -> &'static str {
+    pub fn kind(&self) -> SassResult<&'static str> {
         match self {
-            Value::Color(..) => "color",
+            Value::Color(..) => Ok("color"),
-            Value::Ident(..) => "string",
+            Value::Ident(..) => Ok("string"),
-            Value::Dimension(..) => "number",
+            Value::Dimension(..) => Ok("number"),
-            Value::List(..) => "list",
+            Value::List(..) => Ok("list"),
-            // Value::Function(..) => "function",
+            // Value::Function(..) => Ok("function"),
-            Value::True | Value::False => "bool",
+            Value::True | Value::False => Ok("bool"),
-            Value::Null => "null",
+            Value::Null => Ok("null"),
-            Value::BinaryOp(..) => self.clone().eval().kind(),
+            Value::BinaryOp(..) => self.clone().eval()?.kind(),
-            _ => "unknown",
+            _ => Ok("unknown"),
         }
     }
 
@@ -91,18 +92,18 @@ impl Value {
         }
     }
 
-    pub fn eval(self) -> Self {
+    pub fn eval(self) -> SassResult<Self> {
         match self {
             Self::BinaryOp(lhs, op, rhs) => match op {
                 Op::Plus => *lhs + *rhs,
                 Op::Minus => *lhs - *rhs,
-                Op::Equal => Self::bool(*lhs == *rhs),
+                Op::Equal => Ok(Self::bool(*lhs == *rhs)),
-                Op::NotEqual => Self::bool(*lhs != *rhs),
+                Op::NotEqual => Ok(Self::bool(*lhs != *rhs)),
                 Op::Mul => *lhs * *rhs,
                 Op::Div => *lhs / *rhs,
-                _ => Self::BinaryOp(lhs, op, rhs),
+                _ => Ok(Self::BinaryOp(lhs, op, rhs)),
             },
-            _ => self,
+            _ => Ok(self),
         }
     }
 }

src/value/ops.rs

@@ -1,14 +1,15 @@
 use std::ops::{Add, Div, Mul, Sub};
 
 use crate::common::QuoteKind;
+use crate::error::SassResult;
 use crate::units::Unit;
 use crate::value::Value;
-
+// Undefined operation "red + white".
 impl Add for Value {
-    type Output = Self;
+    type Output = SassResult<Self>;
 
-    fn add(self, other: Self) -> Self {
+    fn add(self, other: Self) -> Self::Output {
-        match self {
+        Ok(match self {
             Self::Important | Self::True | Self::False => match other {
                 Self::Ident(s, QuoteKind::Double) | Self::Ident(s, QuoteKind::Single) => {
                     Value::Ident(format!("{}{}", self, s), QuoteKind::Double)
@@ -77,15 +78,15 @@ impl Add for Value {
                 _ => todo!(),
             },
             _ => todo!(),
-        }
+        })
     }
 }
 
 impl Sub for Value {
-    type Output = Self;
+    type Output = SassResult<Self>;
 
-    fn sub(self, other: Self) -> Self {
+    fn sub(self, other: Self) -> Self::Output {
-        match self {
+        Ok(match self {
             Self::Null => todo!(),
             Self::Dimension(num, unit) => match other {
                 Self::Dimension(num2, unit2) => Value::Dimension(num - num2, unit),
@@ -104,7 +105,7 @@ impl Sub for Value {
                 Self::Dimension(..) => todo!("investigate adding numbers and colors"),
                 _ => Value::Ident(format!("{}-{}", c, other), QuoteKind::None),
             },
-            Self::BinaryOp(..) | Self::Paren(..) => self.eval(),
+            Self::BinaryOp(..) | Self::Paren(..) => self.eval()?,
             Self::Ident(s1, quotes1) => match other {
                 Self::Ident(s2, quotes2) => {
                     let quotes1 = match quotes1 {
@@ -157,30 +158,30 @@ impl Sub for Value {
                 Self::Null => Value::Ident(format!("{}-", self), QuoteKind::None),
                 _ => Value::Ident(format!("{}-{}", self, other), QuoteKind::None),
             },
-        }
+        })
     }
 }
 
 impl Mul for Value {
-    type Output = Self;
+    type Output = SassResult<Self>;
 
-    fn mul(self, other: Self) -> Self {
+    fn mul(self, other: Self) -> Self::Output {
-        match self {
+        Ok(match self {
             Self::Null => todo!(),
             Self::Dimension(num, unit) => match other {
                 Self::Dimension(num2, unit2) => Value::Dimension(num * num2, unit),
                 _ => todo!(),
             },
-            Self::BinaryOp(..) | Self::Paren(..) => self.eval(),
+            Self::BinaryOp(..) | Self::Paren(..) => self.eval()?,
             _ => todo!("incompatible mul types"),
-        }
+        })
     }
 }
 impl Div for Value {
-    type Output = Self;
+    type Output = SassResult<Self>;
 
-    fn div(self, other: Self) -> Self {
+    fn div(self, other: Self) -> Self::Output {
-        match self {
+        Ok(match self {
             Self::Null => todo!(),
             Self::Dimension(num, unit) => match other {
                 Self::Dimension(num2, unit2) => {
@@ -200,7 +201,9 @@ impl Div for Value {
                         QuoteKind::None,
                     )
                 }
-                Self::BinaryOp(..) | Self::Paren(..) => Self::Dimension(num, unit) / other.eval(),
+                Self::BinaryOp(..) | Self::Paren(..) => {
+                    (Self::Dimension(num, unit) / other.eval()?)?
+                }
                 _ => todo!(),
             },
             // Self::List(..) => todo!(),
@@ -216,7 +219,7 @@ impl Div for Value {
                 Self::Dimension(..) => todo!("investigate adding numbers and colors"),
                 _ => Value::Ident(format!("{}/{}", c, other), QuoteKind::None),
             },
-            Self::BinaryOp(..) | Self::Paren(..) => self.eval(),
+            Self::BinaryOp(..) | Self::Paren(..) => self.eval()?,
             Self::Ident(s1, quotes1) => match other {
                 Self::Ident(s2, quotes2) => {
                     let quotes1 = match quotes1 {
@@ -269,6 +272,6 @@ impl Div for Value {
                 Self::Null => Value::Ident(format!("{}/", self), QuoteKind::None),
                 _ => Value::Ident(format!("{}/{}", self, other), QuoteKind::None),
             },
-        }
+        })
     }
 }