Rollup merge of #37102 - est31:rustdoc_question_mark, r=GuillaumeGomez

rustdoc: color the question mark operator

The idea of coloring `?` specially was proposed by @eddyb in: https://github.com/rust-lang/rust/issues/31436#issuecomment-247426582

2 files changed, 10 insertions, 2 deletions

diff --git a/src/librustdoc/html/highlight.rs b/src/librustdoc/html/highlight.rs
index 881352cb73e..d1fe7853445 100644
--- a/src/librustdoc/html/highlight.rs
+++ b/src/librustdoc/html/highlight.rs
@@ -104,6 +104,7 @@ pub enum Class {
     Lifetime,
     PreludeTy,
     PreludeVal,
+    QuestionMark,
 }
 
 /// Trait that controls writing the output of syntax highlighting. Users should
@@ -237,8 +238,10 @@ impl<'a> Classifier<'a> {
             token::Dot | token::DotDot | token::DotDotDot | token::Comma | token::Semi |
                 token::Colon | token::ModSep | token::LArrow | token::OpenDelim(_) |
                 token::CloseDelim(token::Brace) | token::CloseDelim(token::Paren) |
-                token::CloseDelim(token::NoDelim) |
-                token::Question => Class::None,
+                token::CloseDelim(token::NoDelim) => Class::None,
+
+            token::Question => Class::QuestionMark,
+
             token::Dollar => {
                 if self.lexer.peek().tok.is_ident() {
                     self.in_macro_nonterminal = true;
@@ -348,6 +351,7 @@ impl Class {
             Class::Lifetime => "lifetime",
             Class::PreludeTy => "prelude-ty",
             Class::PreludeVal => "prelude-val",
+            Class::QuestionMark => "question-mark"
         }
     }
 }
diff --git a/src/librustdoc/html/static/rustdoc.css b/src/librustdoc/html/static/rustdoc.css
index f8133ea49ce..85ec4fe3f3f 100644
--- a/src/librustdoc/html/static/rustdoc.css
+++ b/src/librustdoc/html/static/rustdoc.css
@@ -570,6 +570,10 @@ pre.rust .self, pre.rust .bool-val, pre.rust .prelude-val,
 pre.rust .attribute, pre.rust .attribute .ident { color: #C82829; }
 pre.rust .macro, pre.rust .macro-nonterminal { color: #3E999F; }
 pre.rust .lifetime { color: #B76514; }
+pre.rust .question-mark {
+    color: #ff9011;
+    font-weight: bold;
+}
 
 .rusttest { display: none; }
 pre.rust { position: relative; }