Refactor associated item resolution more

When resolving an associated item in value namespace, use the `Ty` lowering code
for the segments before the last instead of replicating it.

1 files changed, 54 insertions, 71 deletions

diff --git a/crates/ra_hir/src/ty/infer.rs b/crates/ra_hir/src/ty/infer.rs
index 6aaf61c0e..f33479dc4 100644
--- a/crates/ra_hir/src/ty/infer.rs
+++ b/crates/ra_hir/src/ty/infer.rs
@@ -48,7 +48,7 @@ use crate::{
     resolve::{ResolveValueResult, Resolver, TypeNs, ValueNs},
     ty::infer::diagnostics::InferenceDiagnostic,
     type_ref::{Mutability, TypeRef},
-    Adt, AssocItem, ConstData, DefWithBody, Either, FnData, Function, HasBody, ImplItem, Name, Path,
+    Adt, AssocItem, ConstData, DefWithBody, Either, FnData, Function, HasBody, Name, Path,
     StructField,
 };
 
@@ -508,7 +508,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
     fn resolve_assoc_item(
         &mut self,
-        mut def_or_ty: Either<TypeNs, Ty>,
+        // mut def_or_ty: Either<TypeNs, Ty>,
+        def: TypeNs,
         path: &Path,
         remaining_index: usize,
         id: ExprOrPatId,
@@ -516,80 +517,63 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         assert!(remaining_index < path.segments.len());
         let krate = self.resolver.krate()?;
 
-        let mut ty = Ty::Unknown;
-
-        // resolve intermediate segments
-        for (i, segment) in path.segments[remaining_index..].iter().enumerate() {
-            let is_last_segment = i == path.segments[remaining_index..].len() - 1;
-            ty = match def_or_ty {
-                Either::A(def) => {
-                    let typable: TypableDef = match def {
-                        TypeNs::Adt(it) => it.into(),
-                        TypeNs::TypeAlias(it) => it.into(),
-                        TypeNs::BuiltinType(it) => it.into(),
-                        // FIXME associated item of traits, generics, and Self
-                        TypeNs::Trait(_) | TypeNs::GenericParam(_) | TypeNs::SelfType(_) => {
-                            return None;
-                        }
-                        // FIXME: report error here
-                        TypeNs::EnumVariant(_) => return None,
-                    };
-
-                    let ty = self.db.type_for_def(typable, Namespace::Types);
-
-                    // For example, this substs will take `Gen::*<u32>*::make`
-                    assert!(remaining_index > 0);
-                    let substs = Ty::substs_from_path_segment(
-                        self.db,
-                        &self.resolver,
-                        &path.segments[remaining_index + i - 1],
-                        typable,
-                    );
-                    ty.subst(&substs)
-                }
-                Either::B(ty) => ty,
-            };
-            if is_last_segment {
-                break;
-            }
+        // there may be more intermediate segments between the resolved one and
+        // the end. Only the last segment needs to be resolved to a value; from
+        // the segments before that, we need to get either a type or a trait ref.
 
-            // Attempt to find an impl_item for the type which has a name matching
-            // the current segment
-            log::debug!("looking for path segment: {:?}", segment);
+        let resolved_segment = &path.segments[remaining_index - 1];
+        let remaining_segments = &path.segments[remaining_index..];
+        let is_before_last = remaining_segments.len() == 1;
 
-            let ty = mem::replace(&mut ty, Ty::Unknown);
-            def_or_ty = ty.iterate_impl_items(self.db, krate, |item| {
-                match item {
-                    crate::ImplItem::Method(_) | crate::ImplItem::Const(_) => None,
+        let (def, substs) = match (def, is_before_last) {
+            (TypeNs::Trait(_trait), true) => {
+                // Associated item of trait, e.g. `Default::default`
+                // FIXME
+                return None;
+            }
+            (def, _) => {
+                // Either we already have a type (e.g. `Vec::new`), or we have a
+                // trait but it's not the last segment, so the next segment
+                // should resolve to an associated type of that trait (e.g. `<T
+                // as Iterator>::Item::default`)
+                let remaining_segments_for_ty = &remaining_segments[..remaining_segments.len() - 1];
+                let ty = Ty::from_partly_resolved_hir_path(
+                    self.db,
+                    &self.resolver,
+                    def,
+                    resolved_segment,
+                    remaining_segments_for_ty,
+                );
+                if let Ty::Unknown = ty {
+                    return None;
+                }
 
-                    // FIXME: Resolve associated types
-                    crate::ImplItem::TypeAlias(_) => {
-                        // Some(Either::A(TypeNs::TypeAlias(..)))
-                        None
+                let segment =
+                    remaining_segments.last().expect("there should be at least one segment here");
+                // Find impl
+                let def = ty.clone().iterate_impl_items(self.db, krate, |item| match item {
+                    crate::ImplItem::Method(func) => {
+                        if segment.name == func.name(self.db) {
+                            Some(ValueNs::Function(func))
+                        } else {
+                            None
+                        }
                     }
-                }
-            })?;
-        }
 
-        let segment = path.segments.last().unwrap();
-        let def = ty.clone().iterate_impl_items(self.db, krate, |item| match item {
-            crate::ImplItem::Method(func) => {
-                if segment.name == func.name(self.db) {
-                    Some(ValueNs::Function(func))
-                } else {
-                    None
-                }
+                    crate::ImplItem::Const(konst) => {
+                        if segment.name == konst.name(self.db) {
+                            Some(ValueNs::Const(konst))
+                        } else {
+                            None
+                        }
+                    }
+                    crate::ImplItem::TypeAlias(_) => None,
+                })?;
+                let self_types = self.find_self_types(&def, ty);
+                (def, self_types)
             }
+        };
 
-            crate::ImplItem::Const(konst) => {
-                if konst.name(self.db).map_or(false, |n| n == segment.name) {
-                    Some(ValueNs::Const(konst))
-                } else {
-                    None
-                }
-            }
-            crate::ImplItem::TypeAlias(_) => None,
-        })?;
         self.write_assoc_resolution(
             id,
             match def {
@@ -598,8 +582,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 _ => unreachable!(),
             },
         );
-        let self_types = self.find_self_types(&def, ty);
-        Some((def, self_types))
+        Some((def, substs))
     }
 
     fn find_self_types(&self, def: &ValueNs, actual_def_ty: Ty) -> Option<Substs> {