Merge #2463

2463: More correct method resolution r=flodiebold a=flodiebold

This should fix the order in which candidates for method resolution are considered, i.e. `(&Foo).clone()` should now be of type `Foo` instead of `&Foo`. It also checks for inherent candidates that the self type unifies properly with the self type in the impl (i.e. `impl Foo<u32>` methods will only be considered for `Foo<u32>`).

To be able to get the correct receiver type to check in the method resolution, I needed the unification logic, so I extracted it to the `unify.rs` module.

Should fix #2435.

Co-authored-by: Florian Diebold <[email protected]>

1 files changed, 5 insertions, 37 deletions

diff --git a/crates/ra_hir_ty/src/infer/path.rs b/crates/ra_hir_ty/src/infer/path.rs
index bbf146418..b0024c6e1 100644
--- a/crates/ra_hir_ty/src/infer/path.rs
+++ b/crates/ra_hir_ty/src/infer/path.rs
@@ -57,7 +57,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         let typable: ValueTyDefId = match value {
             ValueNs::LocalBinding(pat) => {
                 let ty = self.result.type_of_pat.get(pat)?.clone();
-                let ty = self.resolve_ty_as_possible(&mut vec![], ty);
+                let ty = self.resolve_ty_as_possible(ty);
                 return Some(ty);
             }
             ValueNs::FunctionId(it) => it.into(),
@@ -206,12 +206,14 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                     AssocItemId::TypeAliasId(_) => unreachable!(),
                 };
                 let substs = match container {
-                    ContainerId::ImplId(_) => self.find_self_types(&def, ty.clone()),
+                    ContainerId::ImplId(impl_id) => {
+                        method_resolution::inherent_impl_substs(self.db, impl_id, &ty)
+                    }
                     ContainerId::TraitId(trait_) => {
                         // we're picking this method
                         let trait_substs = Substs::build_for_def(self.db, trait_)
                             .push(ty.clone())
-                            .fill(std::iter::repeat_with(|| self.new_type_var()))
+                            .fill(std::iter::repeat_with(|| self.table.new_type_var()))
                             .build();
                         let substs = Substs::build_for_def(self.db, item)
                             .use_parent_substs(&trait_substs)
@@ -231,38 +233,4 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             },
         )
     }
-
-    fn find_self_types(&self, def: &ValueNs, actual_def_ty: Ty) -> Option<Substs> {
-        if let ValueNs::FunctionId(func) = *def {
-            // We only do the infer if parent has generic params
-            let gen = self.db.generic_params(func.into());
-            if gen.count_parent_params() == 0 {
-                return None;
-            }
-
-            let impl_id = match func.lookup(self.db).container {
-                ContainerId::ImplId(it) => it,
-                _ => return None,
-            };
-            let self_ty = self.db.impl_self_ty(impl_id).clone();
-            let self_ty_substs = self_ty.substs()?;
-            let actual_substs = actual_def_ty.substs()?;
-
-            let mut new_substs = vec![Ty::Unknown; gen.count_parent_params()];
-
-            // The following code *link up* the function actual parma type
-            // and impl_block type param index
-            self_ty_substs.iter().zip(actual_substs.iter()).for_each(|(param, pty)| {
-                if let Ty::Param { idx, .. } = param {
-                    if let Some(s) = new_substs.get_mut(*idx as usize) {
-                        *s = pty.clone();
-                    }
-                }
-            });
-
-            Some(Substs(new_substs.into()))
-        } else {
-            None
-        }
-    }
 }