diff --git a/src/common.rs b/src/common.rs
index a8bae90..a9827e3 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -454,6 +454,7 @@ impl ListSeparator {
         }
     }
 
+    // Used in currently unimplemented builtin function
     #[allow(dead_code)]
     pub fn name(self) -> &'static str {
         match self {
diff --git a/src/css.rs b/src/css.rs
index 5ad13eb..bdc5955 100644
--- a/src/css.rs
+++ b/src/css.rs
@@ -1,11 +1,12 @@
 //! # Convert from SCSS AST to CSS
+use std::fmt;
+use std::io::Write;
+use std::sync::atomic::Ordering;
+
 use crate::atrule::AtRule;
 use crate::error::SassResult;
 use crate::lexer::IS_UTF8;
 use crate::{RuleSet, Selector, Stmt, Style, StyleSheet};
-use std::fmt;
-use std::io::Write;
-use std::sync::atomic::Ordering;
 
 #[derive(Debug, Clone)]
 enum Toplevel {
@@ -24,8 +25,8 @@ enum BlockEntry {
 impl fmt::Display for BlockEntry {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            BlockEntry::Style(s) => writeln!(f, "  {}", s),
-            BlockEntry::MultilineComment(s) => writeln!(f, "  /*{}*/", s),
+            BlockEntry::Style(s) => writeln!(f, "{}", s),
+            BlockEntry::MultilineComment(s) => writeln!(f, "/*{}*/", s),
         }
     }
 }
@@ -112,8 +113,8 @@ impl Css {
                 } else {
                     self.blocks.push(Toplevel::Newline);
                 }
+                self.blocks.extend(v);
             }
-            self.blocks.extend(v);
         }
         self
     }
@@ -133,7 +134,7 @@ impl Css {
                     has_written = true;
                     writeln!(buf, "{}{} {{", padding, selector)?;
                     for style in styles {
-                        write!(buf, "{}{}", padding, style)?;
+                        write!(buf, "{}  {}", padding, style)?;
                     }
                     writeln!(buf, "{}}}", padding)?;
                 }
@@ -148,7 +149,7 @@ impl Css {
                         } else {
                             writeln!(buf, "{}@{} {} {{", padding, u.name, u.params)?;
                         }
-                        Css::from_stylesheet(StyleSheet::from_stmts(u.body.clone()))
+                        Css::from_stylesheet(StyleSheet::from_stmts(u.body))
                             .pretty_print(buf, nesting + 1)?;
                         writeln!(buf, "{}}}", padding)?;
                     }
diff --git a/src/error.rs b/src/error.rs
index a62a894..9b813b9 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -1,9 +1,10 @@
-use crate::common::Pos;
 use std::error::Error;
 use std::fmt::{self, Display};
 use std::io;
 use std::string::FromUtf8Error;
 
+use crate::common::Pos;
+
 pub type SassResult<T> = Result<T, SassError>;
 
 #[derive(Debug)]
diff --git a/src/imports.rs b/src/imports.rs
index 3cae2e6..f178728 100644
--- a/src/imports.rs
+++ b/src/imports.rs
@@ -1,8 +1,9 @@
+use std::ffi::OsStr;
+use std::path::Path;
+
 use crate::common::Scope;
 use crate::error::SassResult;
 use crate::{Stmt, StyleSheet};
-use std::ffi::OsStr;
-use std::path::Path;
 
 pub(crate) fn import<P: AsRef<Path>>(path: P) -> SassResult<(Vec<Stmt>, Scope)> {
     let mut rules: Vec<Stmt> = Vec::new();
diff --git a/src/lexer.rs b/src/lexer.rs
index 92ef571..ad0b36e 100644
--- a/src/lexer.rs
+++ b/src/lexer.rs
@@ -150,11 +150,6 @@ impl<'a> Iterator for Lexer<'a> {
     }
 }
 
-#[allow(dead_code)]
-fn is_whitespace(c: char) -> bool {
-    c == ' ' || c == '\n' || c == '\r' || c == FORM_FEED
-}
-
 impl<'a> Lexer<'a> {
     pub fn new(buf: &'a str) -> Lexer<'a> {
         Lexer {
@@ -193,20 +188,6 @@ impl<'a> Lexer<'a> {
         }
     }
 
-    #[allow(dead_code)]
-    fn devour_whitespace(&mut self) -> bool {
-        let mut found_whitespace = false;
-        while let Some(c) = self.buf.peek() {
-            if !is_whitespace(*c) {
-                return found_whitespace;
-            }
-            found_whitespace = true;
-            self.buf.next();
-            self.pos.next_char();
-        }
-        found_whitespace
-    }
-
     fn lex_at_rule(&mut self) -> TokenKind {
         self.buf.next();
         self.pos.next_char();
diff --git a/src/lib.rs b/src/lib.rs
index 191b016..b217829 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -78,7 +78,6 @@
     clippy::or_fun_call,
 )]
 #![cfg_attr(feature = "nightly", feature(track_caller))]
-// todo! handle erroring on styles at the toplevel
 use std::fmt::{self, Display};
 use std::fs;
 use std::io::Write;
diff --git a/src/main.rs b/src/main.rs
index 1e03cde..ca03d1d 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,6 +1,7 @@
-use clap::{App, Arg};
 use std::io::{stdout, BufWriter};
 
+use clap::{App, Arg};
+
 use grass::StyleSheet;
 
 fn main() {
diff --git a/src/selector.rs b/src/selector.rs
index f77fcc6..b797fc0 100644
--- a/src/selector.rs
+++ b/src/selector.rs
@@ -1,3 +1,7 @@
+use std::fmt::{self, Display, Write};
+use std::iter::Peekable;
+use std::string::ToString;
+
 use crate::common::{Scope, Symbol, Whitespace};
 use crate::error::SassResult;
 use crate::lexer::Lexer;
@@ -6,9 +10,6 @@ use crate::utils::{
     parse_quoted_string, IsWhitespace,
 };
 use crate::{Token, TokenKind};
-use std::fmt::{self, Display, Write};
-use std::iter::Peekable;
-use std::string::ToString;
 
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub(crate) struct Selector(pub Vec<SelectorKind>);
diff --git a/src/style.rs b/src/style.rs
index 443a973..e92b1da 100644
--- a/src/style.rs
+++ b/src/style.rs
@@ -1,11 +1,12 @@
+use std::fmt::{self, Display};
+use std::iter::Peekable;
+
 use crate::common::{Pos, QuoteKind, Scope, Symbol};
 use crate::error::SassResult;
 use crate::selector::Selector;
 use crate::utils::{devour_whitespace, parse_interpolation, parse_quoted_string};
 use crate::value::Value;
 use crate::{Expr, Token, TokenKind};
-use std::fmt::{self, Display};
-use std::iter::Peekable;
 
 /// A style: `color: red`
 #[derive(Clone, Debug, Eq, PartialEq)]
diff --git a/src/utils.rs b/src/utils.rs
index db9a6f3..50d2d6f 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -1,10 +1,11 @@
+use std::iter::{Iterator, Peekable};
+
 use crate::common::{Keyword, QuoteKind, Symbol};
 use crate::error::SassResult;
 use crate::lexer::Lexer;
 use crate::selector::Selector;
 use crate::value::Value;
 use crate::{Scope, Token, TokenKind};
-use std::iter::{Iterator, Peekable};
 
 pub(crate) trait IsWhitespace {
     fn is_whitespace(&self) -> bool;
diff --git a/src/value/mod.rs b/src/value/mod.rs
index 252810b..988b282 100644
--- a/src/value/mod.rs
+++ b/src/value/mod.rs
@@ -1,4 +1,3 @@
-#![allow(dead_code, unused_variables)]
 use std::fmt::{self, Display, Write};
 use std::iter::Iterator;
 
diff --git a/src/value/ops.rs b/src/value/ops.rs
index c4c0b24..44972f6 100644
--- a/src/value/ops.rs
+++ b/src/value/ops.rs
@@ -22,7 +22,16 @@ impl Add for Value {
                 _ => Value::Ident(format!("{}", other), QuoteKind::None),
             },
             Self::Dimension(num, unit) => match other {
-                Self::Dimension(num2, unit2) => Value::Dimension(num + num2, unit),
+                Self::Dimension(num2, unit2) => {
+                    if !unit.comparable(&unit2) {
+                        return Err(format!("Incompatible units {} and {}.", unit2, unit).into());
+                    }
+                    if unit == unit2 {
+                        Value::Dimension(num + num2, unit)
+                    } else {
+                        todo!("unit conversions")
+                    }
+                }
                 Self::Ident(s, q) => {
                     let quotes = match q {
                         QuoteKind::Double | QuoteKind::Single => QuoteKind::Double,
@@ -99,7 +108,16 @@ impl Sub for Value {
         Ok(match self {
             Self::Null => todo!(),
             Self::Dimension(num, unit) => match other {
-                Self::Dimension(num2, unit2) => Value::Dimension(num - num2, unit),
+                Self::Dimension(num2, unit2) => {
+                    if !unit.comparable(&unit2) {
+                        return Err(format!("Incompatible units {} and {}.", unit2, unit).into());
+                    }
+                    if unit == unit2 {
+                        Value::Dimension(num - num2, unit)
+                    } else {
+                        todo!("unit conversions")
+                    }
+                }
                 _ => todo!(),
             },
             // Self::List(..) => todo!(),
@@ -181,7 +199,22 @@ impl Mul for Value {
         Ok(match self {
             Self::Null => todo!(),
             Self::Dimension(num, unit) => match other {
-                Self::Dimension(num2, unit2) => Value::Dimension(num * num2, unit),
+                Self::Dimension(num2, unit2) => {
+                    if unit2 != Unit::None && unit != Unit::None {
+                        return Err(format!(
+                            "{}{}*{} isn't a valid CSS value.",
+                            num * num2,
+                            unit,
+                            unit2
+                        )
+                        .into());
+                    }
+                    if unit == unit2 {
+                        Value::Dimension(num * num2, unit)
+                    } else {
+                        todo!("unit conversions")
+                    }
+                }
                 _ => {
                     return Err(
                         format!("Undefined operation \"{}{} * {}\".", num, unit, other).into(),
diff --git a/src/value/parse.rs b/src/value/parse.rs
index 47a258b..209cf40 100644
--- a/src/value/parse.rs
+++ b/src/value/parse.rs
@@ -75,7 +75,7 @@ impl Value {
         super_selector: &Selector,
     ) -> SassResult<Self> {
         let left = Self::_from_tokens(toks, scope, super_selector)?;
-        let whitespace = devour_whitespace_or_comment(toks);
+        devour_whitespace_or_comment(toks);
         let next = match toks.peek() {
             Some(x) => x,
             None => return Ok(left),
diff --git a/tests/macros.rs b/tests/macros.rs
index 43b31b4..035d7d4 100644
--- a/tests/macros.rs
+++ b/tests/macros.rs
@@ -1,6 +1,6 @@
 #![cfg(test)]
 
-#[allow(unused_macros)]
+#[macro_export]
 macro_rules! test {
     ($func:ident, $input:literal) => {
         #[test]