`ast::DocCommentsOwner` which represents a documentation comment owner

crates/ra_syntax/src/ast/generated.rs

@@ -864,6 +864,7 @@ impl<'a> AstNode<'a> for FnDef<'a> {
 impl<'a> ast::NameOwner<'a> for FnDef<'a> {}
 impl<'a> ast::TypeParamsOwner<'a> for FnDef<'a> {}
 impl<'a> ast::AttrsOwner<'a> for FnDef<'a> {}
+impl<'a> ast::DocCommentsOwner<'a> for FnDef<'a> {}
 impl<'a> FnDef<'a> {
     pub fn param_list(self) -> Option<ParamList<'a>> {
         super::child_opt(self)

crates/ra_syntax/src/ast/mod.rs

@@ -65,6 +65,24 @@ pub trait AttrsOwner<'a>: AstNode<'a> {
     }
 }
 
+pub trait DocCommentsOwner<'a>: AstNode<'a> {
+    fn doc_comments(self) -> AstChildren<'a, Comment<'a>> { children(self) }
+
+    /// Returns the textual content of a doc comment block as a single string.
+    /// That is, strips leading `///` and joins lines
+    fn doc_comment_text(self) -> String {
+        self.doc_comments()
+            .map(|comment| {
+                let prefix = comment.prefix();
+                let trimmed = comment.text().as_str()
+                    .trim()
+                    .trim_start_matches(prefix)
+                    .trim_start();
+                trimmed.to_owned()
+            }).join("\n")
+    }
+}
+
 impl<'a> FnDef<'a> {
     pub fn has_atom_attr(&self, atom: &str) -> bool {
         self.attrs().filter_map(|x| x.as_atom()).any(|x| x == atom)

crates/ra_syntax/src/grammar.ron

@@ -251,6 +251,7 @@ Grammar(
                 "NameOwner",
                 "TypeParamsOwner",
                 "AttrsOwner",
+                "DocCommentsOwner"
             ],
             options: [ "ParamList", ["body", "Block"], "RetType" ],
         ),