Add semantic highlight to QUESTION token

Made it an operator with controlFlow modifier.

crates/ra_ide/src/syntax_highlighting.rs

@@ -391,6 +391,7 @@ fn highlight_element(
         INT_NUMBER | FLOAT_NUMBER => HighlightTag::NumericLiteral.into(),
         BYTE => HighlightTag::ByteLiteral.into(),
         CHAR => HighlightTag::CharLiteral.into(),
+        QUESTION => Highlight::new(HighlightTag::Operator) | HighlightModifier::ControlFlow,
         LIFETIME => {
             let h = Highlight::new(HighlightTag::Lifetime);
             match element.parent().map(|it| it.kind()) {

crates/ra_ide/src/syntax_highlighting/tags.rs

@@ -42,6 +42,7 @@ pub enum HighlightTag {
     Local,
     UnresolvedReference,
     FormatSpecifier,
+    Operator,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
@@ -89,6 +90,7 @@ impl HighlightTag {
             HighlightTag::Local => "variable",
             HighlightTag::UnresolvedReference => "unresolved_reference",
             HighlightTag::FormatSpecifier => "format_specifier",
+            HighlightTag::Operator => "operator",
         }
     }
 }

crates/rust-analyzer/src/to_proto.rs

@@ -317,6 +317,7 @@ fn semantic_token_type_and_modifiers(
         HighlightTag::Keyword => lsp_types::SemanticTokenType::KEYWORD,
         HighlightTag::UnresolvedReference => semantic_tokens::UNRESOLVED_REFERENCE,
         HighlightTag::FormatSpecifier => semantic_tokens::FORMAT_SPECIFIER,
+        HighlightTag::Operator => lsp_types::SemanticTokenType::OPERATOR,
     };
 
     for modifier in highlight.modifiers.iter() {