markdown: Use the faster hasher (#38469)

Micro-optimisation in the markdown crate to use the faster hasher.

Release Notes:

- N/A

crates/markdown/src/parser.rs

@@ -4,7 +4,9 @@ pub use pulldown_cmark::TagEnd as MarkdownTagEnd;
 use pulldown_cmark::{
     Alignment, CowStr, HeadingLevel, LinkType, MetadataBlockKind, Options, Parser,
 };
-use std::{collections::HashSet, ops::Range, path::Path, sync::Arc};
+use std::{ops::Range, path::Path, sync::Arc};
+
+use collections::HashSet;
 
 use crate::path_range::PathWithRange;
 
@@ -26,8 +28,8 @@ pub fn parse_markdown(
     HashSet<Arc<Path>>,
 ) {
     let mut events = Vec::new();
-    let mut language_names = HashSet::new();
-    let mut language_paths = HashSet::new();
+    let mut language_names = HashSet::default();
+    let mut language_paths = HashSet::default();
     let mut within_link = false;
     let mut within_metadata = false;
     let mut parser = Parser::new_ext(text, PARSE_OPTIONS)
@@ -579,8 +581,8 @@ mod tests {
                     (30..37, Text),
                     (30..37, End(MarkdownTagEnd::Paragraph))
                 ],
-                HashSet::new(),
-                HashSet::new()
+                HashSet::default(),
+                HashSet::default()
             )
         )
     }
@@ -613,8 +615,8 @@ mod tests {
                     (46..51, Text),
                     (0..51, End(MarkdownTagEnd::Paragraph))
                 ],
-                HashSet::new(),
-                HashSet::new()
+                HashSet::default(),
+                HashSet::default()
             )
         );
     }
@@ -670,8 +672,8 @@ mod tests {
                     (43..53, SubstitutedText("–––––".into())),
                     (0..53, End(MarkdownTagEnd::Paragraph))
                 ],
-                HashSet::new(),
-                HashSet::new()
+                HashSet::default(),
+                HashSet::default()
             )
         )
     }
@@ -695,8 +697,12 @@ mod tests {
                     (8..34, Text),
                     (0..37, End(MarkdownTagEnd::CodeBlock)),
                 ],
-                HashSet::from(["rust".into()]),
-                HashSet::new()
+                {
+                    let mut h = HashSet::default();
+                    h.insert("rust".into());
+                    h
+                },
+                HashSet::default()
             )
         );
         assert_eq!(
@@ -716,8 +722,8 @@ mod tests {
                     (4..16, Text),
                     (4..16, End(MarkdownTagEnd::CodeBlock))
                 ],
-                HashSet::new(),
-                HashSet::new()
+                HashSet::default(),
+                HashSet::default()
             )
         );
     }