3 files changed, 61 insertions, 13 deletions

diff --git a/crates/ra_hir/src/code_model_api.rs b/crates/ra_hir/src/code_model_api.rs
index 9ae620efd..333d117f1 100644
--- a/crates/ra_hir/src/code_model_api.rs
+++ b/crates/ra_hir/src/code_model_api.rs
@@ -2,7 +2,7 @@ use std::sync::Arc;
 
 use relative_path::RelativePathBuf;
 use ra_db::{CrateId, FileId};
-use ra_syntax::{ast::{self, AstNode, DocCommentsOwner}, TreeArc, SyntaxNode};
+use ra_syntax::{ast::self, TreeArc, SyntaxNode};
 
 use crate::{
     Name, DefId, Path, PerNs, ScopesWithSyntaxMapping, Ty, HirFileId,
@@ -14,6 +14,7 @@ use crate::{
     adt::VariantData,
     generics::GenericParams,
     code_model_impl::def_id_to_ast,
+    docs::{Documentation, Docs, docs_from_ast}
 };
 
 /// hir::Crate describes a single crate. It's the main interface with which
@@ -208,6 +209,12 @@ impl Struct {
     }
 }
 
+impl Docs for Struct {
+    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
+        docs_from_ast(&*self.source(db).1)
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Enum {
     pub(crate) def_id: DefId,
@@ -239,6 +246,12 @@ impl Enum {
     }
 }
 
+impl Docs for Enum {
+    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
+        docs_from_ast(&*self.source(db).1)
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct EnumVariant {
     pub(crate) def_id: DefId,
@@ -281,6 +294,12 @@ impl EnumVariant {
     }
 }
 
+impl Docs for EnumVariant {
+    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
+        docs_from_ast(&*self.source(db).1)
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Function {
     pub(crate) def_id: DefId,
@@ -352,19 +371,11 @@ impl Function {
     pub fn generic_params(&self, db: &impl HirDatabase) -> Arc<GenericParams> {
         db.generic_params(self.def_id)
     }
+}
 
-    pub fn docs(&self, db: &impl HirDatabase) -> Option<String> {
-        let def_loc = self.def_id.loc(db);
-        let syntax = db.file_item(def_loc.source_item_id);
-        let fn_def = ast::FnDef::cast(&syntax).expect("fn def should point to FnDef node");
-
-        // doc_comment_text unconditionally returns a String
-        let comments = fn_def.doc_comment_text();
-        if comments.is_empty() {
-            None
-        } else {
-            Some(comments)
-        }
+impl Docs for Function {
+    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
+        docs_from_ast(&*self.source(db).1)
     }
 }
 
diff --git a/crates/ra_hir/src/docs.rs b/crates/ra_hir/src/docs.rs
new file mode 100644
index 000000000..330d8f8f4
--- /dev/null
+++ b/crates/ra_hir/src/docs.rs
@@ -0,0 +1,35 @@
+use ra_syntax::ast;
+
+use crate::HirDatabase;
+
+#[derive(Debug, Clone)]
+pub struct Documentation(String);
+
+impl Documentation {
+    pub fn new(s: &str) -> Self {
+        Self(s.into())
+    }
+
+    pub fn contents(&self) -> &str {
+        &self.0
+    }
+}
+
+impl Into<String> for Documentation {
+    fn into(self) -> String {
+        self.contents().into()
+    }
+}
+
+pub trait Docs {
+    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation>;
+}
+
+pub(crate) fn docs_from_ast(node: &impl ast::DocCommentsOwner) -> Option<Documentation> {
+    let comments = node.doc_comment_text();
+    if comments.is_empty() {
+        None
+    } else {
+        Some(Documentation::new(&comments))
+    }
+}
diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index a861ee88e..f517f71e0 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -23,6 +23,7 @@ mod ty;
 mod impl_block;
 mod expr;
 mod generics;
+mod docs;
 
 mod code_model_api;
 mod code_model_impl;
@@ -45,6 +46,7 @@ pub use self::{
     ty::Ty,
     impl_block::{ImplBlock, ImplItem},
     code_model_impl::function::{FnScopes, ScopesWithSyntaxMapping},
+    docs::{Docs, Documentation}
 };
 
 pub use self::code_model_api::{