Support generic function in generate_function assist

crates/hir/src/lib.rs

@@ -2165,6 +2165,16 @@ impl AsAssocItem for ModuleDef {
         }
     }
 }
+impl AsAssocItem for DefWithBody {
+    fn as_assoc_item(self, db: &dyn HirDatabase) -> Option<AssocItem> {
+        match self {
+            DefWithBody::Function(it) => it.as_assoc_item(db),
+            DefWithBody::Const(it) => it.as_assoc_item(db),
+            DefWithBody::Static(_) | DefWithBody::Variant(_) => None,
+        }
+    }
+}
+
 fn as_assoc_item<ID, DEF, CTOR, AST>(db: &dyn HirDatabase, ctor: CTOR, id: ID) -> Option<AssocItem>
 where
     ID: Lookup<Data = AssocItemLoc<AST>>,
@@ -2560,6 +2570,14 @@ impl GenericParam {
             GenericParam::LifetimeParam(it) => it.name(db),
         }
     }
+
+    pub fn parent(self) -> GenericDef {
+        match self {
+            GenericParam::TypeParam(it) => it.id.parent().into(),
+            GenericParam::ConstParam(it) => it.id.parent().into(),
+            GenericParam::LifetimeParam(it) => it.id.parent.into(),
+        }
+    }
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]

crates/ide-assists/src/handlers/generate_delegate_methods.rs

@@ -109,7 +109,7 @@ pub(crate) fn generate_delegate_methods(acc: &mut Assists, ctx: &AssistContext<'
                 let tail_expr_finished =
                     if is_async { make::expr_await(tail_expr) } else { tail_expr };
                 let body = make::block_expr([], Some(tail_expr_finished));
-                let f = make::fn_(vis, name, type_params, params, body, ret_type, is_async)
+                let f = make::fn_(vis, name, type_params, None, params, body, ret_type, is_async)
                     .indent(ast::edit::IndentLevel(1))
                     .clone_for_update();
 

crates/ide-db/src/path_transform.rs

@@ -33,7 +33,7 @@ use syntax::{
 /// }
 /// ```
 pub struct PathTransform<'a> {
-    generic_def: hir::GenericDef,
+    generic_def: Option<hir::GenericDef>,
     substs: Vec<ast::Type>,
     target_scope: &'a SemanticsScope<'a>,
     source_scope: &'a SemanticsScope<'a>,
@@ -49,7 +49,7 @@ impl<'a> PathTransform<'a> {
         PathTransform {
             source_scope,
             target_scope,
-            generic_def: trait_.into(),
+            generic_def: Some(trait_.into()),
             substs: get_syntactic_substs(impl_).unwrap_or_default(),
         }
     }
@@ -63,28 +63,42 @@ impl<'a> PathTransform<'a> {
         PathTransform {
             source_scope,
             target_scope,
-            generic_def: function.into(),
+            generic_def: Some(function.into()),
             substs: get_type_args_from_arg_list(generic_arg_list).unwrap_or_default(),
         }
     }
 
+    pub fn generic_transformation(
+        target_scope: &'a SemanticsScope<'a>,
+        source_scope: &'a SemanticsScope<'a>,
+    ) -> PathTransform<'a> {
+        PathTransform { source_scope, target_scope, generic_def: None, substs: Vec::new() }
+    }
+
     pub fn apply(&self, syntax: &SyntaxNode) {
         self.build_ctx().apply(syntax)
     }
 
+    pub fn apply_all<'b>(&self, nodes: impl IntoIterator<Item = &'b SyntaxNode>) {
+        let ctx = self.build_ctx();
+        for node in nodes {
+            ctx.apply(node);
+        }
+    }
+
     fn build_ctx(&self) -> Ctx<'a> {
         let db = self.source_scope.db;
         let target_module = self.target_scope.module();
         let source_module = self.source_scope.module();
         let skip = match self.generic_def {
             // this is a trait impl, so we need to skip the first type parameter -- this is a bit hacky
-            hir::GenericDef::Trait(_) => 1,
+            Some(hir::GenericDef::Trait(_)) => 1,
             _ => 0,
         };
         let substs_by_param: FxHashMap<_, _> = self
             .generic_def
-            .type_params(db)
             .into_iter()
+            .flat_map(|it| it.type_params(db))
             .skip(skip)
             // The actual list of trait type parameters may be longer than the one
             // used in the `impl` block due to trailing default type parameters.

crates/syntax/src/ast/make.rs

@@ -823,6 +823,7 @@ pub fn fn_(
     visibility: Option<ast::Visibility>,
     fn_name: ast::Name,
     type_params: Option<ast::GenericParamList>,
+    where_clause: Option<ast::WhereClause>,
     params: ast::ParamList,
     body: ast::BlockExpr,
     ret_type: Option<ast::RetType>,
@@ -832,6 +833,10 @@ pub fn fn_(
         Some(type_params) => format!("{type_params}"),
         None => "".into(),
     };
+    let where_clause = match where_clause {
+        Some(it) => format!("{it} "),
+        None => "".into(),
+    };
     let ret_type = match ret_type {
         Some(ret_type) => format!("{ret_type} "),
         None => "".into(),
@@ -844,7 +849,7 @@ pub fn fn_(
     let async_literal = if is_async { "async " } else { "" };
 
     ast_from_text(&format!(
-        "{visibility}{async_literal}fn {fn_name}{type_params}{params} {ret_type}{body}",
+        "{visibility}{async_literal}fn {fn_name}{type_params}{params} {ret_type}{where_clause}{body}",
     ))
 }