1 files changed, 108 insertions, 3 deletions

diff --git a/crates/ra_analysis/src/hover.rs b/crates/ra_analysis/src/hover.rs
index c3825f6ea..c99d87da6 100644
--- a/crates/ra_analysis/src/hover.rs
+++ b/crates/ra_analysis/src/hover.rs
@@ -1,7 +1,11 @@
 use ra_db::{Cancelable, SyntaxDatabase};
-use ra_syntax::{ast, AstNode};
+use ra_syntax::{
+    AstNode, SyntaxNode,
+    ast::{self, NameOwner},
+    algo::visit::{visitor, Visitor},
+};
 
-use crate::{db::RootDatabase, RangeInfo, FilePosition, FileRange};
+use crate::{db::RootDatabase, RangeInfo, FilePosition, FileRange, NavigationTarget};
 
 pub(crate) fn hover(
     db: &RootDatabase,
@@ -10,7 +14,7 @@ pub(crate) fn hover(
     let mut res = Vec::new();
     let range = if let Some(rr) = db.approximately_resolve_symbol(position)? {
         for nav in rr.resolves_to {
-            res.extend(db.doc_text_for(nav)?)
+            res.extend(doc_text_for(db, nav)?)
         }
         rr.reference_range
     } else {
@@ -33,6 +37,107 @@ pub(crate) fn hover(
     Ok(Some(res))
 }
 
+// FIXME: this should not really use navigation target. Rather, approximatelly
+// resovled symbol should return a `DefId`.
+fn doc_text_for(db: &RootDatabase, nav: NavigationTarget) -> Cancelable<Option<String>> {
+    let result = match (nav.description(db), nav.docs(db)) {
+        (Some(desc), Some(docs)) => Some("```rust\n".to_string() + &*desc + "\n```\n\n" + &*docs),
+        (Some(desc), None) => Some("```rust\n".to_string() + &*desc + "\n```"),
+        (None, Some(docs)) => Some(docs),
+        _ => None,
+    };
+
+    Ok(result)
+}
+
+impl NavigationTarget {
+    fn node(&self, db: &RootDatabase) -> Option<SyntaxNode> {
+        let source_file = db.source_file(self.file_id);
+        let source_file = source_file.syntax();
+        let node = source_file
+            .descendants()
+            .find(|node| node.kind() == self.kind && node.range() == self.range)?
+            .owned();
+        Some(node)
+    }
+
+    fn docs(&self, db: &RootDatabase) -> Option<String> {
+        let node = self.node(db)?;
+        let node = node.borrowed();
+        fn doc_comments<'a, N: ast::DocCommentsOwner<'a>>(node: N) -> Option<String> {
+            let comments = node.doc_comment_text();
+            if comments.is_empty() {
+                None
+            } else {
+                Some(comments)
+            }
+        }
+
+        visitor()
+            .visit(doc_comments::<ast::FnDef>)
+            .visit(doc_comments::<ast::StructDef>)
+            .visit(doc_comments::<ast::EnumDef>)
+            .visit(doc_comments::<ast::TraitDef>)
+            .visit(doc_comments::<ast::Module>)
+            .visit(doc_comments::<ast::TypeDef>)
+            .visit(doc_comments::<ast::ConstDef>)
+            .visit(doc_comments::<ast::StaticDef>)
+            .accept(node)?
+    }
+
+    /// Get a description of this node.
+    ///
+    /// e.g. `struct Name`, `enum Name`, `fn Name`
+    fn description(&self, db: &RootDatabase) -> Option<String> {
+        // TODO: After type inference is done, add type information to improve the output
+        let node = self.node(db)?;
+        let node = node.borrowed();
+        // TODO: Refactor to be have less repetition
+        visitor()
+            .visit(|node: ast::FnDef| {
+                let mut string = "fn ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .visit(|node: ast::StructDef| {
+                let mut string = "struct ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .visit(|node: ast::EnumDef| {
+                let mut string = "enum ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .visit(|node: ast::TraitDef| {
+                let mut string = "trait ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .visit(|node: ast::Module| {
+                let mut string = "mod ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .visit(|node: ast::TypeDef| {
+                let mut string = "type ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .visit(|node: ast::ConstDef| {
+                let mut string = "const ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .visit(|node: ast::StaticDef| {
+                let mut string = "static ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .accept(node)?
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use ra_syntax::TextRange;