lazily compute token spans

grass_internal/src/ast/media.rs

@@ -2,7 +2,12 @@ use std::fmt::{self, Write};
 
 use codemap::Span;
 
-use crate::{ast::CssStmt, error::SassResult, lexer::Lexer, parse::MediaQueryParser, token::Token};
+use crate::{
+    ast::CssStmt,
+    error::SassResult,
+    lexer::{Lexer, TokenLexer},
+    parse::MediaQueryParser,
+};
 
 #[derive(Debug, Clone)]
 pub(crate) struct MediaRule {
@@ -54,7 +59,7 @@ impl MediaQuery {
     }
 
     pub fn parse_list(list: &str, span: Span) -> SassResult<Vec<Self>> {
-        let toks = Lexer::new(list.chars().map(|x| Token::new(span, x)).collect(), span);
+        let toks = Lexer::new(TokenLexer::new(list.chars().peekable()).collect(), span);
 
         MediaQueryParser::new(toks).parse()
     }

grass_internal/src/evaluate/visitor.rs

@@ -25,7 +25,7 @@ use crate::{
     common::{unvendor, BinaryOp, Identifier, ListSeparator, QuoteKind, UnaryOp},
     error::{SassError, SassResult},
     interner::InternedString,
-    lexer::Lexer,
+    lexer::{Lexer, TokenLexer},
     parse::{
         AtRootQueryParser, CssParser, KeyframesSelectorParser, SassParser, ScssParser,
         StylesheetParser,
@@ -34,7 +34,6 @@ use crate::{
         ComplexSelectorComponent, ExtendRule, ExtendedSelector, ExtensionStore, SelectorList,
         SelectorParser,
     },
-    token::Token,
     utils::{to_sentence, trim_ascii},
     value::{
         ArgList, CalculationArg, CalculationName, Number, SassCalculation, SassFunction, SassMap,
@@ -978,10 +977,8 @@ impl<'a> Visitor<'a> {
 
                 let span = query.span;
 
-                let query_toks = Lexer::new(
+                let query_toks =
-                    resolved.chars().map(|x| Token::new(span, x)).collect(),
+                    Lexer::new(TokenLexer::new(resolved.chars().peekable()).collect(), span);
-                    span,
-                );
 
                 AtRootQueryParser::new(query_toks).parse()?
             }
@@ -1142,7 +1139,7 @@ impl<'a> Visitor<'a> {
         span: Span,
     ) -> SassResult<SelectorList> {
         let sel_toks = Lexer::new(
-            selector_text.chars().map(|x| Token::new(span, x)).collect(),
+            TokenLexer::new(selector_text.chars().peekable()).collect(),
             span,
         );
 
@@ -2792,7 +2789,7 @@ impl<'a> Visitor<'a> {
         if self.flags.in_keyframes() {
             let span = ruleset.selector_span;
             let sel_toks = Lexer::new(
-                selector_text.chars().map(|x| Token::new(span, x)).collect(),
+                TokenLexer::new(selector_text.chars().peekable()).collect(),
                 span,
             );
             let parsed_selector =

grass_internal/src/lexer.rs

@@ -2,16 +2,19 @@ use std::{borrow::Cow, iter::Peekable, str::Chars, sync::Arc};
 
 use codemap::{File, Span};
 
-use crate::Token;
-
 const FORM_FEED: char = '\x0C';
 
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub(crate) struct Token {
+    pub kind: char,
+    pos: u32,
+}
+
 #[derive(Debug, Clone)]
 // todo: remove lifetime as Cow is now superfluous
 pub(crate) struct Lexer<'a> {
     buf: Cow<'a, [Token]>,
-    /// The span to be used in the case that `buf` is empty
+    entire_span: Span,
-    empty_span: Span,
     cursor: usize,
 }
 
@@ -27,36 +30,35 @@ impl<'a> Lexer<'a> {
         matches!(self.peek(), Some(Token { kind, .. }) if kind == c)
     }
 
-    pub fn span_from(&mut self, start: usize) -> Span {
+    /// Gets the span of the character at the given index. If the index is out of
-        let start = match self.buf.get(start) {
+    /// bounds, it returns the span of the last character. If the input is empty,
-            Some(start) => start.pos,
+    /// it returns an empty span
-            None => return self.current_span(),
+    fn span_at_index(&self, idx: usize) -> Span {
+        let (start, len) = match self.buf.get(idx) {
+            Some(tok) => (tok.pos, tok.kind.len_utf8()),
+            None => match self.buf.last() {
+                Some(tok) => (tok.pos, tok.kind.len_utf8()),
+                None => (0, 0),
+            },
         };
-        self.cursor = self.cursor.saturating_sub(1);
+
-        let end = self.current_span();
+        self.entire_span
-        self.cursor += 1;
+            .subspan(start as u64, start as u64 + len as u64)
+    }
+
+    pub fn span_from(&self, start: usize) -> Span {
+        let start = self.span_at_index(start);
+        let end = self.prev_span();
 
         start.merge(end)
     }
 
     pub fn prev_span(&self) -> Span {
-        match self.buf.get(self.cursor.saturating_sub(1)) {
+        self.span_at_index(self.cursor.saturating_sub(1))
-            Some(tok) => tok.pos,
-            None => match self.buf.last() {
-                Some(tok) => tok.pos,
-                None => self.empty_span,
-            },
-        }
     }
 
     pub fn current_span(&self) -> Span {
-        match self.buf.get(self.cursor) {
+        self.span_at_index(self.cursor)
-            Some(tok) => tok.pos,
-            None => match self.buf.last() {
-                Some(tok) => tok.pos,
-                None => self.empty_span,
-            },
-        }
     }
 
     pub fn peek(&self) -> Option<Token> {
@@ -104,10 +106,16 @@ impl<'a> Iterator for Lexer<'a> {
     }
 }
 
-struct TokenLexer<'a> {
+/// Lex a string into a series of tokens
+pub(crate) struct TokenLexer<'a> {
     buf: Peekable<Chars<'a>>,
-    cursor: usize,
+    cursor: u32,
-    file: Arc<File>,
+}
+
+impl<'a> TokenLexer<'a> {
+    pub fn new(buf: Peekable<Chars<'a>>) -> TokenLexer<'a> {
+        Self { buf, cursor: 0 }
+    }
 }
 
 impl<'a> Iterator for TokenLexer<'a> {
@@ -124,11 +132,8 @@ impl<'a> Iterator for TokenLexer<'a> {
             }
             c => c,
         };
-        let len = kind.len_utf8();
+        let len = kind.len_utf8() as u32;
-        let pos = self
+        let pos = self.cursor;
-            .file
-            .span
-            .subspan(self.cursor as u64, (self.cursor + len) as u64);
         self.cursor += len;
         Some(Token { pos, kind })
     }
@@ -140,21 +145,15 @@ impl<'a> Iterator for TokenLexer<'a> {
 
 impl<'a> Lexer<'a> {
     pub fn new_from_file(file: &Arc<File>) -> Self {
-        let buf = TokenLexer {
+        let buf = TokenLexer::new(file.source().chars().peekable()).collect();
-            file: Arc::clone(file),
+        Self::new(buf, file.span)
-            buf: file.source().chars().peekable(),
-            cursor: 0,
-        }
-        .collect();
-
-        Self::new(buf, file.span.subspan(0, 0))
     }
 
-    pub fn new(buf: Vec<Token>, empty_span: Span) -> Self {
+    pub fn new(buf: Vec<Token>, entire_span: Span) -> Self {
         Lexer {
             buf: Cow::Owned(buf),
             cursor: 0,
-            empty_span,
+            entire_span,
         }
     }
 }

grass_internal/src/lib.rs

@@ -93,7 +93,7 @@ pub use crate::error::{
 };
 pub use crate::fs::{Fs, NullFs, StdFs};
 pub use crate::options::{InputSyntax, Options, OutputStyle};
-pub(crate) use crate::{context_flags::ContextFlags, token::Token};
+pub(crate) use crate::{context_flags::ContextFlags, lexer::Token};
 use crate::{evaluate::Visitor, lexer::Lexer, parse::ScssParser};
 
 mod ast;
@@ -110,7 +110,6 @@ mod options;
 mod parse;
 mod selector;
 mod serializer;
-mod token;
 mod unit;
 mod utils;
 mod value;

grass_internal/src/parse/base.rs

@@ -211,15 +211,15 @@ pub(crate) trait BaseParser<'a> {
     }
 
     fn parse_escape(&mut self, identifier_start: bool) -> SassResult<String> {
+        let start = self.toks().cursor();
         self.expect_char('\\')?;
         let mut value = 0;
         let first = match self.toks().peek() {
             Some(t) => t,
             None => return Err(("Expected expression.", self.toks().current_span()).into()),
         };
-        let mut span = first.pos();
         if first.kind == '\n' {
-            return Err(("Expected escape sequence.", span).into());
+            return Err(("Expected escape sequence.", self.toks().current_span()).into());
         } else if first.kind.is_ascii_hexdigit() {
             for _ in 0..6 {
                 let next = match self.toks().peek() {
@@ -230,7 +230,6 @@ pub(crate) trait BaseParser<'a> {
                     break;
                 }
                 value *= 16;
-                span = span.merge(next.pos);
                 value += as_hex(next.kind);
                 self.toks_mut().next();
             }
@@ -243,12 +242,12 @@ pub(crate) trait BaseParser<'a> {
                 self.toks_mut().next();
             }
         } else {
-            span = span.merge(first.pos);
             value = first.kind as u32;
             self.toks_mut().next();
         }
 
-        let c = std::char::from_u32(value).ok_or(("Invalid Unicode code point.", span))?;
+        let c = std::char::from_u32(value)
+            .ok_or(("Invalid Unicode code point.", self.toks().span_from(start)))?;
         if (identifier_start && is_name_start(c) && !c.is_ascii_digit())
             || (!identifier_start && is_name(c))
         {
@@ -273,8 +272,9 @@ pub(crate) trait BaseParser<'a> {
                 self.toks_mut().next();
                 Ok(())
             }
-            Some(Token { pos, .. }) => Err((format!("expected \"{}\".", c), pos).into()),
+            Some(..) | None => {
-            None => Err((format!("expected \"{}\".", c), self.toks().current_span()).into()),
+                Err((format!("expected \"{}\".", c), self.toks().current_span()).into())
+            }
         }
     }
 
@@ -284,8 +284,7 @@ pub(crate) trait BaseParser<'a> {
                 self.toks_mut().next();
                 Ok(())
             }
-            Some(Token { pos, .. }) => Err((format!("expected {}.", msg), pos).into()),
+            Some(..) | None => Err((format!("expected {}.", msg), self.toks().prev_span()).into()),
-            None => Err((format!("expected {}.", msg), self.toks().prev_span()).into()),
         }
     }
 
@@ -295,8 +294,7 @@ pub(crate) trait BaseParser<'a> {
                 kind: q @ ('\'' | '"'),
                 ..
             }) => q,
-            Some(Token { pos, .. }) => return Err(("Expected string.", pos).into()),
+            Some(..) | None => return Err(("Expected string.", self.toks().current_span()).into()),
-            None => return Err(("Expected string.", self.toks().current_span()).into()),
         };
 
         let mut buffer = String::new();
@@ -346,9 +344,8 @@ pub(crate) trait BaseParser<'a> {
         match self.toks().peek() {
             None => Ok('\u{FFFD}'),
             Some(Token {
-                kind: '\n' | '\r',
+                kind: '\n' | '\r', ..
-                pos,
+            }) => Err(("Expected escape sequence.", self.toks().current_span()).into()),
-            }) => Err(("Expected escape sequence.", pos).into()),
             Some(Token { kind, .. }) if kind.is_ascii_hexdigit() => {
                 let mut value = 0;
                 for _ in 0..6 {

grass_internal/src/parse/keyframes.rs

@@ -1,6 +1,6 @@
 use std::fmt;
 
-use crate::{ast::KeyframesSelector, error::SassResult, lexer::Lexer, token::Token};
+use crate::{ast::KeyframesSelector, error::SassResult, lexer::Lexer, Token};
 
 use super::BaseParser;
 

grass_internal/src/parse/sass.rs

@@ -2,7 +2,7 @@ use std::path::Path;
 
 use codemap::{CodeMap, Span};
 
-use crate::{ast::*, error::SassResult, lexer::Lexer, token::Token, ContextFlags, Options};
+use crate::{ast::*, error::SassResult, lexer::Lexer, Token, ContextFlags, Options};
 
 use super::{BaseParser, StylesheetParser};
 

grass_internal/src/parse/stylesheet.rs

@@ -13,7 +13,7 @@ use crate::{
     ast::*,
     common::{unvendor, Identifier, QuoteKind},
     error::SassResult,
-    lexer::Lexer,
+    lexer::{Lexer, TokenLexer},
     utils::{is_name, is_name_start, is_plain_css_import, opposite_bracket},
     ContextFlags, Options, Token,
 };
@@ -1505,7 +1505,12 @@ pub(crate) trait StylesheetParser<'a>: BaseParser<'a> + Sized {
         self.parse_string()
     }
 
-    fn use_namespace(&mut self, url: &Path, _start: usize) -> SassResult<Option<String>> {
+    fn use_namespace(
+        &mut self,
+        url: &Path,
+        _start: usize,
+        url_span: Span,
+    ) -> SassResult<Option<String>> {
         if self.scan_identifier("as", false)? {
             self.whitespace()?;
             return Ok(if self.scan_char('*') {
@@ -1530,11 +1535,8 @@ pub(crate) trait StylesheetParser<'a>: BaseParser<'a> + Sized {
         };
 
         let mut toks = Lexer::new(
-            namespace
+            TokenLexer::new(namespace.chars().peekable()).collect(),
-                .chars()
+            url_span,
-                .map(|x| Token::new(self.span_before(), x))
-                .collect(),
-            self.span_before(),
         );
 
         // if namespace is empty, avoid attempting to parse an identifier from
@@ -1630,12 +1632,14 @@ pub(crate) trait StylesheetParser<'a>: BaseParser<'a> + Sized {
     }
 
     fn parse_use_rule(&mut self, start: usize) -> SassResult<AstStmt> {
+        let url_start = self.toks().cursor();
         let url = self.parse_url_string()?;
+        let url_span = self.toks().span_from(url_start);
         self.whitespace()?;
 
         let path = PathBuf::from(url);
 
-        let namespace = self.use_namespace(path.as_ref(), start)?;
+        let namespace = self.use_namespace(path.as_ref(), start, url_span)?;
         self.whitespace()?;
         let configuration = self.parse_configuration(false)?;
 

grass_internal/src/parse/value.rs

@@ -229,12 +229,12 @@ impl<'a, 'c, P: StylesheetParser<'a>> ValueParser<'a, 'c, P> {
                         parser,
                     )?;
                 }
-                Some(Token { kind: '*', pos }) => {
+                Some(Token { kind: '*', .. }) => {
                     parser.toks_mut().next();
                     self.add_operator(
                         Spanned {
                             node: BinaryOp::Mul,
-                            span: pos,
+                            span: parser.toks().current_span(),
                         },
                         parser,
                     )?;
@@ -304,12 +304,12 @@ impl<'a, 'c, P: StylesheetParser<'a>> ValueParser<'a, 'c, P> {
                         )?;
                     }
                 }
-                Some(Token { kind: '%', pos }) => {
+                Some(Token { kind: '%', .. }) => {
                     parser.toks_mut().next();
                     self.add_operator(
                         Spanned {
                             node: BinaryOp::Rem,
-                            span: pos,
+                            span: parser.toks().current_span(),
                         },
                         parser,
                     )?;
@@ -1019,12 +1019,12 @@ impl<'a, 'c, P: StylesheetParser<'a>> ValueParser<'a, 'c, P> {
         }
 
         match parser.toks().peek_n(1) {
-            Some(Token { kind, pos }) if !kind.is_ascii_digit() => {
+            Some(Token { kind, .. }) if !kind.is_ascii_digit() => {
                 if allow_trailing_dot {
                     return Ok(None);
                 }
 
-                return Err(("Expected digit.", pos).into());
+                return Err(("Expected digit.", parser.toks().current_span()).into());
             }
             Some(..) => {}
             None => return Err(("Expected digit.", parser.toks().current_span()).into()),
@@ -1234,12 +1234,14 @@ impl<'a, 'c, P: StylesheetParser<'a>> ValueParser<'a, 'c, P> {
                     .span(parser.toks_mut().span_from(start)))
                 } else {
                     let arguments = parser.parse_argument_invocation(false, false)?;
-                    Ok(AstExpr::InterpolatedFunction(Arc::new(InterpolatedFunction {
+                    Ok(
+                        AstExpr::InterpolatedFunction(Arc::new(InterpolatedFunction {
                             name: identifier,
                             arguments,
                             span: parser.toks_mut().span_from(start),
                         }))
-                    .span(parser.toks_mut().span_from(start)))
+                        .span(parser.toks_mut().span_from(start)),
+                    )
                 }
             }
             _ => Ok(AstExpr::String(
@@ -1625,7 +1627,7 @@ impl<'a, 'c, P: StylesheetParser<'a>> ValueParser<'a, 'c, P> {
             match parser.toks().peek() {
                 Some(Token {
                     kind: next @ ('+' | '-'),
-                    pos,
+                    ..
                 }) => {
                     if !matches!(
                         parser.toks().peek_n_backwards(1),
@@ -1642,7 +1644,7 @@ impl<'a, 'c, P: StylesheetParser<'a>> ValueParser<'a, 'c, P> {
                     ) {
                         return Err((
                             "\"+\" and \"-\" must be surrounded by whitespace in calculations.",
-                            pos,
+                            parser.toks().current_span(),
                         )
                             .into());
                     }

grass_internal/src/token.rs

@@ -1,19 +0,0 @@
-use codemap::Span;
-
-// todo: remove span from tokens
-
-#[derive(Copy, Clone, Debug, Eq, PartialEq)]
-pub(crate) struct Token {
-    pub pos: Span,
-    pub kind: char,
-}
-
-impl Token {
-    pub const fn new(pos: Span, kind: char) -> Self {
-        Self { pos, kind }
-    }
-
-    pub const fn pos(&self) -> Span {
-        self.pos
-    }
-}

grass_internal/src/value/mod.rs

@@ -312,15 +312,11 @@ impl Value {
 
     pub fn cmp(&self, other: &Self, span: Span, op: BinaryOp) -> SassResult<Option<Ordering>> {
         Ok(match self {
-            Value::Dimension(SassNumber {
+            Value::Dimension(SassNumber { num, unit, .. }) => match &other {
-                num,
-                unit,
-                as_slash: _,
-            }) => match &other {
                 Value::Dimension(SassNumber {
                     num: num2,
                     unit: unit2,
-                    as_slash: _,
+                    ..
                 }) => {
                     if !unit.comparable(unit2) {
                         return Err(