Differentiate Tuple / FnPtr type constructors by cardinality

This is necessary because Chalk (reasonably) expects each 'struct' to know how
many type parameters it takes.

crates/ra_hir/src/ty.rs

@@ -82,13 +82,13 @@ pub enum TypeCtor {
     /// fn foo() -> i32 { 1 }
     /// let bar: fn() -> i32 = foo;
     /// ```
-    FnPtr,
+    FnPtr { num_args: u16 },
 
     /// The never type `!`.
     Never,
 
     /// A tuple type.  For example, `(i32, bool)`.
-    Tuple,
+    Tuple { cardinality: u16 },
 }
 
 /// A nominal type with (maybe 0) type parameters. This might be a primitive
@@ -299,7 +299,7 @@ impl Ty {
         Ty::Apply(ApplicationTy { ctor, parameters })
     }
     pub fn unit() -> Self {
-        Ty::apply(TypeCtor::Tuple, Substs::empty())
+        Ty::apply(TypeCtor::Tuple { cardinality: 0 }, Substs::empty())
     }
 
     pub fn walk(&self, f: &mut impl FnMut(&Ty)) {
@@ -352,7 +352,9 @@ impl Ty {
 
     pub fn as_tuple(&self) -> Option<&Substs> {
         match self {
-            Ty::Apply(ApplicationTy { ctor: TypeCtor::Tuple, parameters }) => Some(parameters),
+            Ty::Apply(ApplicationTy { ctor: TypeCtor::Tuple { .. }, parameters }) => {
+                Some(parameters)
+            }
             _ => None,
         }
     }
@@ -380,7 +382,7 @@ impl Ty {
     fn callable_sig(&self, db: &impl HirDatabase) -> Option<FnSig> {
         match self {
             Ty::Apply(a_ty) => match a_ty.ctor {
-                TypeCtor::FnPtr => Some(FnSig::from_fn_ptr_substs(&a_ty.parameters)),
+                TypeCtor::FnPtr { .. } => Some(FnSig::from_fn_ptr_substs(&a_ty.parameters)),
                 TypeCtor::FnDef(def) => {
                     let sig = db.callable_item_signature(def);
                     Some(sig.subst(&a_ty.parameters))
@@ -466,7 +468,7 @@ impl HirDisplay for ApplicationTy {
                 write!(f, "&{}{}", m.as_keyword_for_ref(), t.display(f.db))?;
             }
             TypeCtor::Never => write!(f, "!")?,
-            TypeCtor::Tuple => {
+            TypeCtor::Tuple { .. } => {
                 let ts = &self.parameters;
                 if ts.len() == 1 {
                     write!(f, "({},)", ts[0].display(f.db))?;
@@ -476,7 +478,7 @@ impl HirDisplay for ApplicationTy {
                     write!(f, ")")?;
                 }
             }
-            TypeCtor::FnPtr => {
+            TypeCtor::FnPtr { .. } => {
                 let sig = FnSig::from_fn_ptr_substs(&self.parameters);
                 write!(f, "fn(")?;
                 f.write_joined(sig.params(), ", ")?;

crates/ra_hir/src/ty/infer.rs

@@ -739,14 +739,14 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 };
                 let expectations_iter = expectations.iter().chain(repeat(&Ty::Unknown));
 
-                let inner_tys = args
+                let inner_tys: Substs = args
                     .iter()
                     .zip(expectations_iter)
                     .map(|(&pat, ty)| self.infer_pat(pat, ty, default_bm))
                     .collect::<Vec<_>>()
                     .into();
 
-                Ty::apply(TypeCtor::Tuple, Substs(inner_tys))
+                Ty::apply(TypeCtor::Tuple { cardinality: inner_tys.len() as u16 }, inner_tys)
             }
             Pat::Ref { pat, mutability } => {
                 let expectation = match expected.as_reference() {
@@ -1073,7 +1073,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                     .autoderef(self.db)
                     .find_map(|derefed_ty| match derefed_ty {
                         Ty::Apply(a_ty) => match a_ty.ctor {
-                            TypeCtor::Tuple => {
+                            TypeCtor::Tuple { .. } => {
                                 let i = name.to_string().parse::<usize>().ok();
                                 i.and_then(|i| a_ty.parameters.0.get(i).cloned())
                             }
@@ -1184,7 +1184,10 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                     ty_vec.push(self.infer_expr(*arg, &Expectation::none()));
                 }
 
-                Ty::apply(TypeCtor::Tuple, Substs(ty_vec.into()))
+                Ty::apply(
+                    TypeCtor::Tuple { cardinality: ty_vec.len() as u16 },
+                    Substs(ty_vec.into()),
+                )
             }
             Expr::Array(array) => {
                 let elem_ty = match &expected.ty {

crates/ra_hir/src/ty/lower.rs

@@ -29,7 +29,10 @@ impl Ty {
             TypeRef::Tuple(inner) => {
                 let inner_tys =
                     inner.iter().map(|tr| Ty::from_hir(db, resolver, tr)).collect::<Vec<_>>();
-                Ty::apply(TypeCtor::Tuple, Substs(inner_tys.into()))
+                Ty::apply(
+                    TypeCtor::Tuple { cardinality: inner_tys.len() as u16 },
+                    Substs(inner_tys.into()),
+                )
             }
             TypeRef::Path(path) => Ty::from_hir_path(db, resolver, path),
             TypeRef::RawPtr(inner, mutability) => {
@@ -53,7 +56,7 @@ impl Ty {
                 let inner_tys =
                     params.iter().map(|tr| Ty::from_hir(db, resolver, tr)).collect::<Vec<_>>();
                 let sig = Substs(inner_tys.into());
-                Ty::apply(TypeCtor::FnPtr, sig)
+                Ty::apply(TypeCtor::FnPtr { num_args: sig.len() as u16 - 1 }, sig)
             }
             TypeRef::Error => Ty::Unknown,
         }

crates/ra_hir/src/ty/traits/chalk.rs

@@ -184,6 +184,7 @@ where
         debug!("struct_datum {:?}", struct_id);
         let type_ctor = from_chalk(self.db, struct_id);
         // FIXME might be nicer if we can create a fake GenericParams for the TypeCtor
+        // FIXME extract this to a method on Ty
         let (num_params, upstream) = match type_ctor {
             TypeCtor::Bool
             | TypeCtor::Char
@@ -192,7 +193,8 @@ where
             | TypeCtor::Never
             | TypeCtor::Str => (0, true),
             TypeCtor::Slice | TypeCtor::Array | TypeCtor::RawPtr(_) | TypeCtor::Ref(_) => (1, true),
-            TypeCtor::FnPtr | TypeCtor::Tuple => unimplemented!(), // FIXME tuples and FnPtr are currently variadic... we need to make the parameter number explicit
+            TypeCtor::FnPtr { num_args } => (num_args as usize + 1, true),
+            TypeCtor::Tuple { cardinality } => (cardinality as usize, true),
             TypeCtor::FnDef(_) => unimplemented!(),
             TypeCtor::Adt(adt) => {
                 let generic_params = adt.generic_params(self.db);

crates/ra_ide_api/src/completion/complete_dot.rs

@@ -24,7 +24,7 @@ fn complete_fields(acc: &mut Completions, ctx: &CompletionContext, receiver: Ty)
                     }
                 }
                 // FIXME unions
-                TypeCtor::Tuple => {
+                TypeCtor::Tuple { .. } => {
                     for (i, ty) in a_ty.parameters.iter().enumerate() {
                         acc.add_pos_field(ctx, i, ty);
                     }