3 files changed, 33 insertions, 27 deletions

diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index 2ea3b341f..e659f903c 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -89,13 +89,13 @@ pub enum Ty {
     /// fn foo() -> i32 { 1 }
     /// let bar: fn() -> i32 = foo;
     /// ```
-    FnPtr(FnSig),
+    FnPtr(Substs),
 
     /// The never type `!`.
     Never,
 
     /// A tuple type.  For example, `(i32, bool)`.
-    Tuple(Arc<[Ty]>),
+    Tuple(Substs),
 
     /// A type parameter; for example, `T` in `fn f<T>(x: T) {}
     Param {
@@ -127,6 +127,10 @@ impl Substs {
         Substs(Arc::new([]))
     }
 
+    pub fn iter(&self) -> impl Iterator<Item = &Ty> {
+        self.0.iter()
+    }
+
     pub fn walk_mut(&mut self, f: &mut impl FnMut(&mut Ty)) {
         // Without an Arc::make_mut_slice, we can't avoid the clone here:
         let mut v: Vec<_> = self.0.iter().cloned().collect();
@@ -148,6 +152,11 @@ impl FnSig {
         params.push(ret);
         FnSig { params_and_return: params.into() }
     }
+
+    pub fn from_fn_ptr_substs(substs: &Substs) -> FnSig {
+        FnSig { params_and_return: Arc::clone(&substs.0) }
+    }
+
     pub fn params(&self) -> &[Ty] {
         &self.params_and_return[0..self.params_and_return.len() - 1]
     }
@@ -168,7 +177,7 @@ impl FnSig {
 
 impl Ty {
     pub fn unit() -> Self {
-        Ty::Tuple(Arc::new([]))
+        Ty::Tuple(Substs::empty())
     }
 
     pub fn walk(&self, f: &mut impl FnMut(&Ty)) {
@@ -182,10 +191,9 @@ impl Ty {
                 }
             }
             Ty::FnPtr(sig) => {
-                for input in sig.params() {
-                    input.walk(f);
+                for t in sig.iter() {
+                    t.walk(f);
                 }
-                sig.ret().walk(f);
             }
             Ty::FnDef { substs, .. } => {
                 for t in substs.0.iter() {
@@ -216,12 +224,7 @@ impl Ty {
             Ty::RawPtr(t, _) => Arc::make_mut(t).walk_mut(f),
             Ty::Ref(t, _) => Arc::make_mut(t).walk_mut(f),
             Ty::Tuple(ts) => {
-                // Without an Arc::make_mut_slice, we can't avoid the clone here:
-                let mut v: Vec<_> = ts.iter().cloned().collect();
-                for t in &mut v {
-                    t.walk_mut(f);
-                }
-                *ts = v.into();
+                ts.walk_mut(f);
             }
             Ty::FnPtr(sig) => {
                 sig.walk_mut(f);
@@ -324,15 +327,16 @@ impl HirDisplay for Ty {
             }
             Ty::Never => write!(f, "!")?,
             Ty::Tuple(ts) => {
-                if ts.len() == 1 {
-                    write!(f, "({},)", ts[0].display(f.db))?;
+                if ts.0.len() == 1 {
+                    write!(f, "({},)", ts.0[0].display(f.db))?;
                 } else {
                     write!(f, "(")?;
-                    f.write_joined(&**ts, ", ")?;
+                    f.write_joined(&*ts.0, ", ")?;
                     write!(f, ")")?;
                 }
             }
             Ty::FnPtr(sig) => {
+                let sig = FnSig::from_fn_ptr_substs(sig);
                 write!(f, "fn(")?;
                 f.write_joined(sig.params(), ", ")?;
                 write!(f, ") -> {}", sig.ret().display(f.db))?;
diff --git a/crates/ra_hir/src/ty/infer.rs b/crates/ra_hir/src/ty/infer.rs
index 735cdecb9..69af8fb92 100644
--- a/crates/ra_hir/src/ty/infer.rs
+++ b/crates/ra_hir/src/ty/infer.rs
@@ -38,7 +38,7 @@ use crate::{
     resolve::{Resolver, Resolution},
     nameres::Namespace
 };
-use super::{Ty, TypableDef, Substs, primitive, op};
+use super::{Ty, TypableDef, Substs, primitive, op, FnSig};
 
 /// The entry point of type inference.
 pub fn infer(db: &impl HirDatabase, func: Function) -> Arc<InferenceResult> {
@@ -257,10 +257,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 self.unify_inner(t1, t2, depth + 1)
             }
             (Ty::Ref(t1, m1), Ty::Ref(t2, m2)) if m1 == m2 => self.unify_inner(t1, t2, depth + 1),
-            (Ty::FnPtr(sig1), Ty::FnPtr(sig2)) if sig1 == sig2 => true,
-            (Ty::Tuple(ts1), Ty::Tuple(ts2)) if ts1.len() == ts2.len() => {
-                ts1.iter().zip(ts2.iter()).all(|(t1, t2)| self.unify_inner(t1, t2, depth + 1))
-            }
+            (Ty::FnPtr(sig1), Ty::FnPtr(sig2)) => self.unify_substs(sig1, sig2, depth + 1),
+            (Ty::Tuple(ts1), Ty::Tuple(ts2)) => self.unify_substs(ts1, ts2, depth + 1),
             (Ty::Infer(InferTy::TypeVar(tv1)), Ty::Infer(InferTy::TypeVar(tv2)))
             | (Ty::Infer(InferTy::IntVar(tv1)), Ty::Infer(InferTy::IntVar(tv2)))
             | (Ty::Infer(InferTy::FloatVar(tv1)), Ty::Infer(InferTy::FloatVar(tv2))) => {
@@ -632,7 +630,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         let ty = match &body[pat] {
             Pat::Tuple(ref args) => {
                 let expectations = match *expected {
-                    Ty::Tuple(ref tuple_args) => &**tuple_args,
+                    Ty::Tuple(ref tuple_args) => &*tuple_args.0,
                     _ => &[],
                 };
                 let expectations_iter = expectations.iter().chain(repeat(&Ty::Unknown));
@@ -644,7 +642,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                     .collect::<Vec<_>>()
                     .into();
 
-                Ty::Tuple(inner_tys)
+                Ty::Tuple(Substs(inner_tys))
             }
             Pat::Ref { pat, mutability } => {
                 let expectation = match *expected {
@@ -789,7 +787,10 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             Expr::Call { callee, args } => {
                 let callee_ty = self.infer_expr(*callee, &Expectation::none());
                 let (param_tys, ret_ty) = match &callee_ty {
-                    Ty::FnPtr(sig) => (sig.params().to_vec(), sig.ret().clone()),
+                    Ty::FnPtr(sig) => {
+                        let sig = FnSig::from_fn_ptr_substs(sig);
+                        (sig.params().to_vec(), sig.ret().clone())
+                    }
                     Ty::FnDef { substs, def, .. } => {
                         let sig = self.db.callable_item_signature(*def);
                         let ret_ty = sig.ret().clone().subst(&substs);
@@ -828,6 +829,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 let method_ty = self.insert_type_vars(method_ty);
                 let (expected_receiver_ty, param_tys, ret_ty) = match &method_ty {
                     Ty::FnPtr(sig) => {
+                        let sig = FnSig::from_fn_ptr_substs(sig);
                         if !sig.params().is_empty() {
                             (sig.params()[0].clone(), sig.params()[1..].to_vec(), sig.ret().clone())
                         } else {
@@ -923,7 +925,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                     .find_map(|derefed_ty| match derefed_ty {
                         Ty::Tuple(fields) => {
                             let i = name.to_string().parse::<usize>().ok();
-                            i.and_then(|i| fields.get(i).cloned())
+                            i.and_then(|i| fields.0.get(i).cloned())
                         }
                         Ty::Adt { def_id: AdtDef::Struct(s), ref substs, .. } => {
                             s.field(self.db, name).map(|field| {
@@ -1016,7 +1018,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                     ty_vec.push(self.infer_expr(*arg, &Expectation::none()));
                 }
 
-                Ty::Tuple(Arc::from(ty_vec))
+                Ty::Tuple(Substs(ty_vec.into()))
             }
             Expr::Array { exprs } => {
                 let elem_ty = match &expected.ty {
diff --git a/crates/ra_hir/src/ty/lower.rs b/crates/ra_hir/src/ty/lower.rs
index 389a2fc68..20e6273a6 100644
--- a/crates/ra_hir/src/ty/lower.rs
+++ b/crates/ra_hir/src/ty/lower.rs
@@ -30,7 +30,7 @@ impl Ty {
             TypeRef::Tuple(inner) => {
                 let inner_tys =
                     inner.iter().map(|tr| Ty::from_hir(db, resolver, tr)).collect::<Vec<_>>();
-                Ty::Tuple(inner_tys.into())
+                Ty::Tuple(Substs(inner_tys.into()))
             }
             TypeRef::Path(path) => Ty::from_hir_path(db, resolver, path),
             TypeRef::RawPtr(inner, mutability) => {
@@ -53,7 +53,7 @@ impl Ty {
             TypeRef::Fn(params) => {
                 let inner_tys =
                     params.iter().map(|tr| Ty::from_hir(db, resolver, tr)).collect::<Vec<_>>();
-                let sig = FnSig { params_and_return: inner_tys.into() };
+                let sig = Substs(inner_tys.into());
                 Ty::FnPtr(sig)
             }
             TypeRef::Error => Ty::Unknown,