Add new AttributeExt::opt_style method

Author: GuillaumeGomez

compiler/rustc_ast/src/attr/mod.rs

@@ -206,8 +206,8 @@ impl AttributeExt for Attribute {
         }
     }
 
-    fn style(&self) -> AttrStyle {
-        self.style
+    fn opt_style(&self) -> Option<AttrStyle> {
+        Some(self.style)
     }
 }
 
@@ -806,7 +806,14 @@ pub trait AttributeExt: Debug {
     /// * `#[doc(...)]` returns `None`.
     fn doc_str_and_comment_kind(&self) -> Option<(Symbol, CommentKind)>;
 
-    fn style(&self) -> AttrStyle;
+    fn style(&self) -> AttrStyle {
+        match self.opt_style() {
+            Some(style) => style,
+            None => panic!("AttributeExt::style: `{self:?}` has no style"),
+        }
+    }
+
+    fn opt_style(&self) -> Option<AttrStyle>;
 }
 
 // FIXME(fn_delegation): use function delegation instead of manually forwarding

compiler/rustc_hir/src/hir.rs

@@ -1245,11 +1245,11 @@ impl AttributeExt for Attribute {
     }
 
     #[inline]
-    fn style(&self) -> AttrStyle {
+    fn opt_style(&self) -> Option<AttrStyle> {
         match &self {
-            Attribute::Unparsed(u) => u.style,
-            Attribute::Parsed(AttributeKind::DocComment { style, .. }) => *style,
-            _ => panic!(),
+            Attribute::Unparsed(u) => Some(u.style),
+            Attribute::Parsed(AttributeKind::DocComment { style, .. }) => Some(*style),
+            _ => None,
         }
     }
 }
@@ -1345,6 +1345,11 @@ impl Attribute {
     pub fn style(&self) -> AttrStyle {
         AttributeExt::style(self)
     }
+
+    #[inline]
+    pub fn opt_style(&self) -> Option<AttrStyle> {
+        AttributeExt::opt_style(self)
+    }
 }
 
 /// Attributes owned by a HIR owner.