docs: describe new feature 'add custom impl for derived trait'

1 files changed, 17 insertions, 0 deletions

diff --git a/crates/ra_assists/src/assists/add_custom_impl.rs b/crates/ra_assists/src/assists/add_custom_impl.rs
index 7e64cd902..037306fd6 100644
--- a/crates/ra_assists/src/assists/add_custom_impl.rs
+++ b/crates/ra_assists/src/assists/add_custom_impl.rs
@@ -12,6 +12,23 @@ use ra_syntax::{
 
 const DERIVE_TRAIT: &'static str = "derive";
 
+// Assist: add_custom_impl
+//
+// Adds impl block for derived trait.
+//
+// ```
+// #[derive(Deb<|>ug, Display)]
+// struct S;
+// ```
+// ->
+// ```
+// #[derive(Display)]
+// struct S;
+//
+// impl Debug for S {
+//
+// }
+// ```
 pub(crate) fn add_custom_impl(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let input = ctx.find_node_at_offset::<ast::AttrInput>()?;
     let attr = input.syntax().parent().and_then(ast::Attr::cast)?;