From b4bb7743810b1e6ac8b897a465c430e9ed8d5c44 Mon Sep 17 00:00:00 2001
From: Lukas Wirth <lukastw97@gmail.com>
Date: Mon, 29 Mar 2021 18:39:58 +0200
Subject: Remove TraitRef::Error

---
 crates/hir_def/src/item_tree/lower.rs | 11 +++++++----
 crates/hir_def/src/type_ref.rs        | 16 +++++++---------
 crates/hir_ty/src/lower.rs            |  5 +----
 3 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/crates/hir_def/src/item_tree/lower.rs b/crates/hir_def/src/item_tree/lower.rs
index 4b2af564e..8d3862811 100644
--- a/crates/hir_def/src/item_tree/lower.rs
+++ b/crates/hir_def/src/item_tree/lower.rs
@@ -536,7 +536,10 @@ impl Ctx {
     fn lower_impl(&mut self, impl_def: &ast::Impl) -> Option<FileItemTreeId<Impl>> {
         let generic_params =
             self.lower_generic_params_and_inner_items(GenericsOwner::Impl, impl_def);
-        let target_trait = impl_def.trait_().map(|tr| self.lower_trait_ref(&tr));
+        // FIXME: If trait lowering fails, due to a non PathType for example, we treat this impl
+        // as if it was an non-trait impl. Ideally we want to create a unique missing ref that only
+        // equals itself.
+        let target_trait = impl_def.trait_().and_then(|tr| self.lower_trait_ref(&tr));
         let self_ty = self.lower_type_ref(&impl_def.self_ty()?);
         let is_negative = impl_def.excl_token().is_some();
 
@@ -740,9 +743,9 @@ impl Ctx {
         self.data().vis.alloc(vis)
     }
 
-    fn lower_trait_ref(&mut self, trait_ref: &ast::Type) -> Idx<TraitRef> {
-        let trait_ref = TraitRef::from_ast(&self.body_ctx, trait_ref.clone());
-        self.data().trait_refs.intern(trait_ref)
+    fn lower_trait_ref(&mut self, trait_ref: &ast::Type) -> Option<Idx<TraitRef>> {
+        let trait_ref = TraitRef::from_ast(&self.body_ctx, trait_ref.clone())?;
+        Some(self.data().trait_refs.intern(trait_ref))
     }
 
     fn lower_type_ref(&mut self, type_ref: &ast::Type) -> Idx<TypeRef> {
diff --git a/crates/hir_def/src/type_ref.rs b/crates/hir_def/src/type_ref.rs
index b7484ed0d..4c24aae94 100644
--- a/crates/hir_def/src/type_ref.rs
+++ b/crates/hir_def/src/type_ref.rs
@@ -52,21 +52,19 @@ impl Rawness {
 }
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
-pub enum TraitRef {
-    Path(Path),
-    Error,
+pub struct TraitRef {
+    pub path: Path,
 }
 
 impl TraitRef {
     /// Converts an `ast::PathType` to a `hir::TraitRef`.
-    pub(crate) fn from_ast(ctx: &LowerCtx, node: ast::Type) -> Self {
+    pub(crate) fn from_ast(ctx: &LowerCtx, node: ast::Type) -> Option<Self> {
         // FIXME: Use `Path::from_src`
         match node {
-            ast::Type::PathType(path) => path
-                .path()
-                .and_then(|it| ctx.lower_path(it))
-                .map_or(TraitRef::Error, TraitRef::Path),
-            _ => TraitRef::Error,
+            ast::Type::PathType(path) => {
+                path.path().and_then(|it| ctx.lower_path(it)).map(|path| TraitRef { path })
+            }
+            _ => None,
         }
     }
 }
diff --git a/crates/hir_ty/src/lower.rs b/crates/hir_ty/src/lower.rs
index ee627e125..afbfa12d5 100644
--- a/crates/hir_ty/src/lower.rs
+++ b/crates/hir_ty/src/lower.rs
@@ -670,10 +670,7 @@ impl<'a> TyLoweringContext<'a> {
         trait_ref: &HirTraitRef,
         explicit_self_ty: Option<Ty>,
     ) -> Option<TraitRef> {
-        match trait_ref {
-            HirTraitRef::Path(path) => self.lower_trait_ref_from_path(path, explicit_self_ty),
-            HirTraitRef::Error => None,
-        }
+        self.lower_trait_ref_from_path(&trait_ref.path, explicit_self_ty)
     }
 
     fn trait_ref_substs_from_path(
-- 
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