3 files changed, 62 insertions, 66 deletions

diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index 861d6aefe..cf16ed94d 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -196,7 +196,7 @@ impl Module {
     /// `None` for the crate root.
     pub fn declaration_source(
         self,
-        db: &impl HirDatabase,
+        db: &(impl DefDatabase + AstDatabase),
     ) -> Option<(HirFileId, TreeArc<ast::Module>)> {
         let def_map = db.crate_def_map(self.krate);
         let decl = def_map[self.module_id].declaration?;
diff --git a/crates/ra_hir/src/db.rs b/crates/ra_hir/src/db.rs
index 3afd0994c..d2a372f3b 100644
--- a/crates/ra_hir/src/db.rs
+++ b/crates/ra_hir/src/db.rs
@@ -127,6 +127,9 @@ pub trait DefDatabase: SourceDatabase {
 
     #[salsa::invoke(crate::lang_item::LangItems::lang_item_query)]
     fn lang_item(&self, start_crate: Crate, item: SmolStr) -> Option<LangItemTarget>;
+
+    #[salsa::invoke(crate::docs::documentation_query)]
+    fn documentation(&self, def: crate::docs::DocDef) -> Option<crate::docs::Documentation>;
 }
 
 #[salsa::query_group(HirDatabaseStorage)]
diff --git a/crates/ra_hir/src/docs.rs b/crates/ra_hir/src/docs.rs
index 38c0922eb..900fd2aa8 100644
--- a/crates/ra_hir/src/docs.rs
+++ b/crates/ra_hir/src/docs.rs
@@ -1,10 +1,44 @@
+use std::sync::Arc;
+
 use ra_syntax::ast;
 
-use crate::{HirDatabase, Module, StructField, Struct, Enum, EnumVariant, Static, Const, Function, Union, Trait, TypeAlias, FieldSource};
+use crate::{
+    HirDatabase, DefDatabase, AstDatabase,
+    Module, StructField, Struct, Enum, EnumVariant, Static, Const, Function, Union, Trait, TypeAlias, FieldSource
+};
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum DocDef {
+    Module(Module),
+    StructField(StructField),
+    Struct(Struct),
+    Enum(Enum),
+    EnumVariant(EnumVariant),
+    Static(Static),
+    Const(Const),
+    Function(Function),
+    Union(Union),
+    Trait(Trait),
+    TypeAlias(TypeAlias),
+}
+
+impl_froms!(
+    DocDef: Module,
+    StructField,
+    Struct,
+    Enum,
+    EnumVariant,
+    Static,
+    Const,
+    Function,
+    Union,
+    Trait,
+    TypeAlias
+);
 
 /// Holds documentation
-#[derive(Debug, Clone)]
-pub struct Documentation(String);
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Documentation(Arc<str>);
 
 impl Documentation {
     fn new(s: &str) -> Documentation {
@@ -12,13 +46,13 @@ impl Documentation {
     }
 
     pub fn as_str(&self) -> &str {
-        &self.0
+        &*self.0
     }
 }
 
 impl Into<String> for Documentation {
     fn into(self) -> String {
-        self.0.clone()
+        self.as_str().to_owned()
     }
 }
 
@@ -30,71 +64,30 @@ pub(crate) fn docs_from_ast(node: &impl ast::DocCommentsOwner) -> Option<Documen
     node.doc_comment_text().map(|it| Documentation::new(&it))
 }
 
-impl Docs for Module {
-    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
-        self.declaration_source(db).and_then(|it| docs_from_ast(&*it.1))
-    }
-}
-
-impl Docs for StructField {
-    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
-        match self.source(db).1 {
+pub(crate) fn documentation_query(
+    db: &(impl DefDatabase + AstDatabase),
+    def: DocDef,
+) -> Option<Documentation> {
+    match def {
+        DocDef::Module(it) => docs_from_ast(&*it.declaration_source(db)?.1),
+        DocDef::StructField(it) => match it.source(db).1 {
             FieldSource::Named(named) => docs_from_ast(&*named),
             FieldSource::Pos(..) => return None,
-        }
-    }
-}
-
-impl Docs for Struct {
-    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
-        docs_from_ast(&*self.source(db).1)
-    }
-}
-
-impl Docs for Union {
-    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
-        docs_from_ast(&*self.source(db).1)
-    }
-}
-
-impl Docs for Enum {
-    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
-        docs_from_ast(&*self.source(db).1)
-    }
-}
-
-impl Docs for EnumVariant {
-    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
-        docs_from_ast(&*self.source(db).1)
-    }
-}
-
-impl Docs for Function {
-    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
-        docs_from_ast(&*self.source(db).1)
-    }
-}
-
-impl Docs for Const {
-    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
-        docs_from_ast(&*self.source(db).1)
-    }
-}
-
-impl Docs for Static {
-    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
-        docs_from_ast(&*self.source(db).1)
-    }
-}
-
-impl Docs for Trait {
-    fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
-        docs_from_ast(&*self.source(db).1)
+        },
+        DocDef::Struct(it) => docs_from_ast(&*it.source(db).1),
+        DocDef::Enum(it) => docs_from_ast(&*it.source(db).1),
+        DocDef::EnumVariant(it) => docs_from_ast(&*it.source(db).1),
+        DocDef::Static(it) => docs_from_ast(&*it.source(db).1),
+        DocDef::Const(it) => docs_from_ast(&*it.source(db).1),
+        DocDef::Function(it) => docs_from_ast(&*it.source(db).1),
+        DocDef::Union(it) => docs_from_ast(&*it.source(db).1),
+        DocDef::Trait(it) => docs_from_ast(&*it.source(db).1),
+        DocDef::TypeAlias(it) => docs_from_ast(&*it.source(db).1),
     }
 }
 
-impl Docs for TypeAlias {
+impl<T: Into<DocDef> + Copy> Docs for T {
     fn docs(&self, db: &impl HirDatabase) -> Option<Documentation> {
-        docs_from_ast(&*self.source(db).1)
+        db.documentation((*self).into())
     }
 }