Rollup merge of #89538 - notriddle:notriddle/arrow-highlight, r=GuillaumeGomez

Make rustdoc not highlight `->` and `=>` as operators

It was marking them up as `<span class="op">=</span><span class="op">&gt;</span>`,
which is bloaty and wrong (at least, I think `<=` and `=>` should probably be different colors, since they're so different and yet made from the same symbols).

Before:

![image](https://user-images.githubusercontent.com/1593513/135939748-f49b0f9e-6a7d-4d65-935a-e31cdf688a81.png)

After:

![image](https://user-images.githubusercontent.com/1593513/135940063-5ef1f6b1-7e03-4227-b46b-572b063aba05.png)

src/librustdoc/html/highlight.rs

@@ -435,7 +435,27 @@ impl<'a> Classifier<'a> {
                 _ => Class::RefKeyWord,
             },
 
-            // Operators.
+            // These can either be operators, or arrows.
+            TokenKind::Eq => match lookahead {
+                Some(TokenKind::Eq) => {
+                    self.next();
+                    sink(Highlight::Token { text: "==", class: Some(Class::Op) });
+                    return;
+                }
+                Some(TokenKind::Gt) => {
+                    self.next();
+                    sink(Highlight::Token { text: "=>", class: None });
+                    return;
+                }
+                _ => Class::Op,
+            },
+            TokenKind::Minus if lookahead == Some(TokenKind::Gt) => {
+                self.next();
+                sink(Highlight::Token { text: "->", class: None });
+                return;
+            }
+
+            // Other operators.
             TokenKind::Minus
             | TokenKind::Plus
             | TokenKind::Or
@@ -443,7 +463,6 @@ impl<'a> Classifier<'a> {
             | TokenKind::Caret
             | TokenKind::Percent
             | TokenKind::Bang
-            | TokenKind::Eq
             | TokenKind::Lt
             | TokenKind::Gt => Class::Op,
 

src/librustdoc/html/highlight/fixtures/sample.html

@@ -13,7 +13,7 @@
 <span class="kw">use</span> <span class="ident">std::path</span>::{<span class="ident">Path</span>, <span class="ident">PathBuf</span>};
 
 <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">target_os</span> <span class="op">=</span> <span class="string">&quot;linux&quot;</span>)]</span>
-<span class="kw">fn</span> <span class="ident">main</span>() {
+<span class="kw">fn</span> <span class="ident">main</span>() -&gt; () {
     <span class="kw">let</span> <span class="ident">foo</span> <span class="op">=</span> <span class="bool-val">true</span> <span class="op">&amp;&amp;</span> <span class="bool-val">false</span> <span class="op">|</span><span class="op">|</span> <span class="bool-val">true</span>;
     <span class="kw">let</span> <span class="kw">_</span>: <span class="kw-2">*</span><span class="kw">const</span> () <span class="op">=</span> <span class="number">0</span>;
     <span class="kw">let</span> <span class="kw">_</span> <span class="op">=</span> <span class="kw-2">&amp;</span><span class="ident">foo</span>;
@@ -27,11 +27,11 @@
     <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">s</span> <span class="op">=</span> <span class="ident">String::new</span>();
 
     <span class="kw">match</span> <span class="kw-2">&amp;</span><span class="ident">s</span> {
-        <span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span><span class="op">&gt;</span> {}
+        <span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">x</span> =&gt; {}
     }
 }
 
 <span class="macro">macro_rules!</span> <span class="ident">bar</span> {
-    (<span class="macro-nonterminal">$</span><span class="macro-nonterminal">foo</span>:<span class="ident">tt</span>) <span class="op">=</span><span class="op">&gt;</span> {};
+    (<span class="macro-nonterminal">$</span><span class="macro-nonterminal">foo</span>:<span class="ident">tt</span>) =&gt; {};
 }
 </code></pre>

src/librustdoc/html/highlight/fixtures/sample.rs

@@ -3,7 +3,7 @@
 use std::path::{Path, PathBuf};
 
 #[cfg(target_os = "linux")]
-fn main() {
+fn main() -> () {
     let foo = true && false || true;
     let _: *const () = 0;
     let _ = &foo;

src/test/rustdoc/macro_rules-matchers.rs

@@ -6,37 +6,31 @@
 // @has 'foo/macro.todo.html'
 // @has - '//span[@class="macro"]' 'macro_rules!'
 // @has - '//span[@class="ident"]' 'todo'
-// Note: count = 2 * ('=' + '>') + '+' = 2 * (1 + 1) + 1 = 5
-// @count - '//pre[@class="rust macro"]//span[@class="op"]' 5
+// Note: the only op is the `+`
+// @count - '//pre[@class="rust macro"]//span[@class="op"]' 1
 
-// @has - '{ ()'
-// @has - '//span[@class="op"]' '='
-// @has - '//span[@class="op"]' '>'
-// @has - '{ ... };'
-
-// @has - '($('
+// @has - '{ () => { ... }; ($('
 // @has - '//span[@class="macro-nonterminal"]' '$'
 // @has - '//span[@class="macro-nonterminal"]' 'arg'
 // @has - ':'
 // @has - '//span[@class="ident"]' 'tt'
 // @has - '),'
 // @has - '//span[@class="op"]' '+'
-// @has - ')'
+// @has - ') => { ... }; }'
 pub use std::todo;
 
 mod mod1 {
     // @has 'foo/macro.macro1.html'
     // @has - 'macro_rules!'
     // @has - 'macro1'
-    // @has - '{ ()'
-    // @has - '($('
+    // @has - '{ () => { ... }; ($('
     // @has - '//span[@class="macro-nonterminal"]' '$'
     // @has - '//span[@class="macro-nonterminal"]' 'arg'
     // @has - ':'
     // @has - 'expr'
     // @has - '),'
     // @has - '+'
-    // @has - ')'
+    // @has - ') => { ... }; }'
     #[macro_export]
     macro_rules! macro1 {
         () => {};