Have to_generic_args return ast::GenericArgList

Author: DropDemBits

crates/syntax/src/ast/edit_in_place.rs

@@ -236,21 +236,22 @@ impl ast::GenericParamList {
         }
     }
 
-    /// Extracts the const, type, and lifetime names into a new [`ast::GenericParamList`]
-    pub fn to_generic_args(&self) -> ast::GenericParamList {
-        let params = self.generic_params().filter_map(|param| match param {
-            ast::GenericParam::ConstParam(it) => {
-                Some(ast::GenericParam::TypeParam(make::type_param(it.name()?, None)))
-            }
+    /// Constructs a matching [`ast::GenericArgList`]
+    pub fn to_generic_args(&self) -> ast::GenericArgList {
+        let args = self.generic_params().filter_map(|param| match param {
             ast::GenericParam::LifetimeParam(it) => {
-                Some(ast::GenericParam::LifetimeParam(make::lifetime_param(it.lifetime()?)))
+                Some(ast::GenericArg::LifetimeArg(make::lifetime_arg(it.lifetime()?)))
             }
             ast::GenericParam::TypeParam(it) => {
-                Some(ast::GenericParam::TypeParam(make::type_param(it.name()?, None)))
+                Some(ast::GenericArg::TypeArg(make::type_arg(make::ext::ty_name(it.name()?))))
+            }
+            ast::GenericParam::ConstParam(it) => {
+                // Name-only const params get parsed as `TypeArg`s
+                Some(ast::GenericArg::TypeArg(make::type_arg(make::ext::ty_name(it.name()?))))
             }
         });
 
-        make::generic_param_list(params)
+        make::generic_arg_list(args)
     }
 }
 
@@ -317,7 +318,7 @@ impl Removable for ast::TypeBoundList {
 impl ast::PathSegment {
     pub fn get_or_create_generic_arg_list(&self) -> ast::GenericArgList {
         if self.generic_arg_list().is_none() {
-            let arg_list = make::generic_arg_list().clone_for_update();
+            let arg_list = make::generic_arg_list(empty()).clone_for_update();
             ted::append_child(self.syntax(), arg_list.syntax());
         }
         self.generic_arg_list().unwrap()

crates/syntax/src/ast/make.rs

@@ -88,6 +88,9 @@ pub mod ext {
         block_expr(None, None)
     }
 
+    pub fn ty_name(name: ast::Name) -> ast::Type {
+        ty_path(ident_path(&format!("{name}")))
+    }
     pub fn ty_bool() -> ast::Type {
         ty_path(ident_path("bool"))
     }
@@ -160,6 +163,7 @@ pub fn assoc_item_list() -> ast::AssocItemList {
     ast_from_text("impl C for D {}")
 }
 
+// FIXME: `ty_params` should be `ast::GenericArgList`
 pub fn impl_(
     ty: ast::Path,
     params: Option<ast::GenericParamList>,
@@ -185,10 +189,6 @@ pub fn impl_trait(
     ast_from_text(&format!("impl{ty_params} {trait_} for {ty}{ty_params} {{}}"))
 }
 
-pub(crate) fn generic_arg_list() -> ast::GenericArgList {
-    ast_from_text("const S: T<> = ();")
-}
-
 pub fn path_segment(name_ref: ast::NameRef) -> ast::PathSegment {
     ast_from_text(&format!("type __ = {name_ref};"))
 }
@@ -718,6 +718,21 @@ pub fn generic_param_list(
     ast_from_text(&format!("fn f<{args}>() {{ }}"))
 }
 
+pub fn type_arg(ty: ast::Type) -> ast::TypeArg {
+    ast_from_text(&format!("const S: T<{ty}> = ();"))
+}
+
+pub fn lifetime_arg(lifetime: ast::Lifetime) -> ast::LifetimeArg {
+    ast_from_text(&format!("const S: T<{lifetime}> = ();"))
+}
+
+pub(crate) fn generic_arg_list(
+    args: impl IntoIterator<Item = ast::GenericArg>,
+) -> ast::GenericArgList {
+    let args = args.into_iter().join(", ");
+    ast_from_text(&format!("const S: T<{args}> = ();"))
+}
+
 pub fn visibility_pub_crate() -> ast::Visibility {
     ast_from_text("pub(crate) struct S")
 }