More FxHashMap usage

src/side_by_side.rs

@@ -1,10 +1,8 @@
 //! Side-by-side (two column) display of diffs.
 
 use owo_colors::{OwoColorize, Style};
-use std::{
-    cmp::max,
-    collections::{HashMap, HashSet},
-};
+use rustc_hash::FxHashMap;
+use std::{cmp::max, collections::HashSet};
 
 use crate::{
     constants::Side,
@@ -250,21 +248,19 @@ fn highlight_positions(
     lhs_mps: &[MatchedPos],
     rhs_mps: &[MatchedPos],
 ) -> (
-    HashMap<LineNumber, Vec<(SingleLineSpan, Style)>>,
-    HashMap<LineNumber, Vec<(SingleLineSpan, Style)>>,
+    FxHashMap<LineNumber, Vec<(SingleLineSpan, Style)>>,
+    FxHashMap<LineNumber, Vec<(SingleLineSpan, Style)>>,
 ) {
     let lhs_positions = color_positions(true, background, syntax_highlight, lhs_mps);
     // Preallocate the hashmap assuming the average line will have 2 items on it.
-    let mut lhs_styles: HashMap<LineNumber, Vec<(SingleLineSpan, Style)>> =
-        HashMap::with_capacity(lhs_positions.len() / 2);
+    let mut lhs_styles: FxHashMap<LineNumber, Vec<(SingleLineSpan, Style)>> = FxHashMap::default();
     for (span, style) in lhs_positions {
         let styles = lhs_styles.entry(span.line).or_insert_with(Vec::new);
         styles.push((span, style));
     }
 
     let rhs_positions = color_positions(false, background, syntax_highlight, rhs_mps);
-    let mut rhs_styles: HashMap<LineNumber, Vec<(SingleLineSpan, Style)>> =
-        HashMap::with_capacity(rhs_positions.len() / 2);
+    let mut rhs_styles: FxHashMap<LineNumber, Vec<(SingleLineSpan, Style)>> = FxHashMap::default();
     for (span, style) in rhs_positions {
         let styles = rhs_styles.entry(span.line).or_insert_with(Vec::new);
         styles.push((span, style));
@@ -367,7 +363,7 @@ pub fn print(
             rhs_mps,
         )
     } else {
-        (HashMap::new(), HashMap::new())
+        (FxHashMap::default(), FxHashMap::default())
     };
 
     let lhs_lines = split_on_newlines(lhs_src);

src/style.rs

@@ -8,10 +8,8 @@ use crate::{
     syntax::{AtomKind, MatchKind, MatchedPos, TokenKind},
 };
 use owo_colors::{OwoColorize, Style};
-use std::{
-    cmp::{max, min},
-    collections::HashMap,
-};
+use rustc_hash::FxHashMap;
+use std::cmp::{max, min};
 
 #[derive(Clone, Copy, Debug)]
 pub enum BackgroundColor {
@@ -196,8 +194,8 @@ fn apply_line(line: &str, styles: &[(SingleLineSpan, Style)]) -> String {
 
 fn group_by_line(
     ranges: &[(SingleLineSpan, Style)],
-) -> HashMap<LineNumber, Vec<(SingleLineSpan, Style)>> {
-    let mut ranges_by_line: HashMap<_, Vec<_>> = HashMap::with_capacity(ranges.len());
+) -> FxHashMap<LineNumber, Vec<(SingleLineSpan, Style)>> {
+    let mut ranges_by_line: FxHashMap<_, Vec<_>> = FxHashMap::default();
     for range in ranges {
         if let Some(matching_ranges) = ranges_by_line.get_mut(&range.0.line) {
             (*matching_ranges).push(*range);