4 files changed, 23 insertions, 42 deletions

diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index bf7445ea3..cc9746f6d 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -17,7 +17,7 @@ use std::sync::Arc;
 use std::{fmt, iter, mem};
 
 use crate::{
-    db::HirDatabase, expr::ExprId, type_ref::Mutability, util::make_mut_arc_slice, Adt, Crate,
+    db::HirDatabase, expr::ExprId, type_ref::Mutability, util::make_mut_slice, Adt, Crate,
     DefWithBody, GenericParams, HasGenericParams, Name, Trait, TypeAlias,
 };
 use display::{HirDisplay, HirFormatter};
@@ -308,11 +308,9 @@ impl Substs {
     }
 
     pub fn walk_mut(&mut self, f: &mut impl FnMut(&mut Ty)) {
-        make_mut_arc_slice(&mut self.0, |s| {
-            for t in s {
-                t.walk_mut(f);
-            }
-        });
+        for t in make_mut_slice(&mut self.0) {
+            t.walk_mut(f);
+        }
     }
 
     pub fn as_single(&self) -> &Ty {
@@ -538,11 +536,9 @@ impl TypeWalk for FnSig {
     }
 
     fn walk_mut(&mut self, f: &mut impl FnMut(&mut Ty)) {
-        make_mut_arc_slice(&mut self.params_and_return, |s| {
-            for t in s {
-                t.walk_mut(f);
-            }
-        });
+        for t in make_mut_slice(&mut self.params_and_return) {
+            t.walk_mut(f);
+        }
     }
 }
 
@@ -752,11 +748,9 @@ impl TypeWalk for Ty {
                 p_ty.parameters.walk_mut(f);
             }
             Ty::Dyn(predicates) | Ty::Opaque(predicates) => {
-                make_mut_arc_slice(predicates, |s| {
-                    for p in s {
-                        p.walk_mut(f);
-                    }
-                });
+                for p in make_mut_slice(predicates) {
+                    p.walk_mut(f);
+                }
             }
             Ty::Param { .. } | Ty::Bound(_) | Ty::Infer(_) | Ty::Unknown => {}
         }
diff --git a/crates/ra_hir/src/ty/infer/unify.rs b/crates/ra_hir/src/ty/infer/unify.rs
index 5e86ed260..014c7981f 100644
--- a/crates/ra_hir/src/ty/infer/unify.rs
+++ b/crates/ra_hir/src/ty/infer/unify.rs
@@ -6,7 +6,7 @@ use crate::ty::{
     Canonical, InEnvironment, InferTy, ProjectionPredicate, ProjectionTy, Substs, TraitRef, Ty,
     TypeWalk,
 };
-use crate::util::make_mut_arc_slice;
+use crate::util::make_mut_slice;
 
 impl<'a, D: HirDatabase> InferenceContext<'a, D> {
     pub(super) fn canonicalizer<'b>(&'b mut self) -> Canonicalizer<'a, 'b, D>
@@ -76,11 +76,9 @@ where
     }
 
     fn do_canonicalize_trait_ref(&mut self, mut trait_ref: TraitRef) -> TraitRef {
-        make_mut_arc_slice(&mut trait_ref.substs.0, |tys| {
-            for ty in tys {
-                *ty = self.do_canonicalize_ty(ty.clone());
-            }
-        });
+        for ty in make_mut_slice(&mut trait_ref.substs.0) {
+            *ty = self.do_canonicalize_ty(ty.clone());
+        }
         trait_ref
     }
 
@@ -92,11 +90,9 @@ where
     }
 
     fn do_canonicalize_projection_ty(&mut self, mut projection_ty: ProjectionTy) -> ProjectionTy {
-        make_mut_arc_slice(&mut projection_ty.parameters.0, |params| {
-            for ty in params {
-                *ty = self.do_canonicalize_ty(ty.clone());
-            }
-        });
+        for ty in make_mut_slice(&mut projection_ty.parameters.0) {
+            *ty = self.do_canonicalize_ty(ty.clone());
+        }
         projection_ty
     }
 
diff --git a/crates/ra_hir/src/ty/lower.rs b/crates/ra_hir/src/ty/lower.rs
index 639518f27..366556134 100644
--- a/crates/ra_hir/src/ty/lower.rs
+++ b/crates/ra_hir/src/ty/lower.rs
@@ -22,7 +22,7 @@ use crate::{
     resolve::{Resolver, TypeNs},
     ty::Adt,
     type_ref::{TypeBound, TypeRef},
-    util::make_mut_arc_slice,
+    util::make_mut_slice,
     BuiltinType, Const, Enum, EnumVariant, Function, ModuleDef, Path, Static, Struct, StructField,
     Trait, TypeAlias, Union,
 };
@@ -391,9 +391,7 @@ impl TraitRef {
     ) -> Self {
         let mut substs = TraitRef::substs_from_path(db, resolver, segment, resolved);
         if let Some(self_ty) = explicit_self_ty {
-            make_mut_arc_slice(&mut substs.0, |substs| {
-                substs[0] = self_ty;
-            });
+            make_mut_slice(&mut substs.0)[0] = self_ty;
         }
         TraitRef { trait_: resolved, substs }
     }
diff --git a/crates/ra_hir/src/util.rs b/crates/ra_hir/src/util.rs
index 46f423c91..0095ee45d 100644
--- a/crates/ra_hir/src/util.rs
+++ b/crates/ra_hir/src/util.rs
@@ -4,16 +4,9 @@ use std::sync::Arc;
 
 /// Helper for mutating `Arc<[T]>` (i.e. `Arc::make_mut` for Arc slices).
 /// The underlying values are cloned if there are other strong references.
-pub(crate) fn make_mut_arc_slice<T: Clone, R>(
-    a: &mut Arc<[T]>,
-    f: impl FnOnce(&mut [T]) -> R,
-) -> R {
-    if let Some(s) = Arc::get_mut(a) {
-        f(s)
-    } else {
-        let mut v = a.to_vec();
-        let r = f(&mut v);
-        *a = Arc::from(v);
-        r
+pub(crate) fn make_mut_slice<T: Clone>(a: &mut Arc<[T]>) -> &mut [T] {
+    if Arc::get_mut(a).is_none() {
+        *a = a.iter().cloned().collect();
     }
+    Arc::get_mut(a).unwrap()
 }