feature: add the "Recursively add derive" assist

crates/hir/src/lib.rs

@@ -409,6 +409,20 @@ impl ModuleDef {
         acc
     }
 
+    pub fn as_trait(self) -> Option<Trait> {
+        match self {
+            ModuleDef::Trait(it) => Some(it),
+            _ => None,
+        }
+    }
+
+    pub fn as_macro(self) -> Option<Macro> {
+        match self {
+            ModuleDef::Macro(it) => Some(it),
+            _ => None,
+        }
+    }
+
     pub fn as_def_with_body(self) -> Option<DefWithBody> {
         match self {
             ModuleDef::Function(it) => Some(it.into()),
@@ -2997,6 +3011,13 @@ impl ItemInNs {
         }
     }
 
+    pub fn as_macro(self) -> Option<Macro> {
+        match self {
+            ItemInNs::Types(_) | ItemInNs::Values(_) => None,
+            ItemInNs::Macros(id) => Some(id),
+        }
+    }
+
     /// Returns the crate defining this item (or `None` if `self` is built-in).
     pub fn krate(&self, db: &dyn HirDatabase) -> Option<Crate> {
         match self {

crates/hir/src/semantics.rs

@@ -99,6 +99,13 @@ impl PathResolution {
             PathResolution::SelfType(impl_def) => Some(TypeNs::SelfType((*impl_def).into())),
         }
     }
+
+    pub fn as_module_def(&self) -> Option<ModuleDef> {
+        match self {
+            PathResolution::Def(it) => Some(*it),
+            _ => None,
+        }
+    }
 }
 
 #[derive(Debug)]