7 files changed, 65 insertions, 19 deletions

diff --git a/crates/ra_hir_ty/src/diagnostics/expr.rs b/crates/ra_hir_ty/src/diagnostics/expr.rs
index 21ff99a8c..557d01cdc 100644
--- a/crates/ra_hir_ty/src/diagnostics/expr.rs
+++ b/crates/ra_hir_ty/src/diagnostics/expr.rs
@@ -175,6 +175,10 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
         };
 
         let sig = db.callable_item_signature(callee);
+        if sig.value.is_varargs {
+            return None;
+        }
+
         let params = sig.value.params();
 
         let mut param_count = params.len();
@@ -512,4 +516,30 @@ impl Foo {
         "#,
         );
     }
+
+    #[test]
+    fn varargs() {
+        check_diagnostics(
+            r#"
+extern "C" {
+    fn fixed(fixed: u8);
+    fn varargs(fixed: u8, ...);
+    fn varargs2(...);
+}
+
+fn f() {
+    unsafe {
+        fixed(0);
+        fixed(0, 1);
+      //^^^^^^^^^^^ Expected 1 argument, found 2
+        varargs(0);
+        varargs(0, 1);
+        varargs2();
+        varargs2(0);
+        varargs2(0, 1);
+    }
+}
+        "#,
+        )
+    }
 }
diff --git a/crates/ra_hir_ty/src/display.rs b/crates/ra_hir_ty/src/display.rs
index ac68c5661..c860c254c 100644
--- a/crates/ra_hir_ty/src/display.rs
+++ b/crates/ra_hir_ty/src/display.rs
@@ -243,10 +243,17 @@ impl HirDisplay for ApplicationTy {
                     write!(f, ")")?;
                 }
             }
-            TypeCtor::FnPtr { .. } => {
-                let sig = FnSig::from_fn_ptr_substs(&self.parameters);
+            TypeCtor::FnPtr { is_varargs, .. } => {
+                let sig = FnSig::from_fn_ptr_substs(&self.parameters, is_varargs);
                 write!(f, "fn(")?;
                 f.write_joined(sig.params(), ", ")?;
+                if is_varargs {
+                    if sig.params().is_empty() {
+                        write!(f, "...")?;
+                    } else {
+                        write!(f, ", ...")?;
+                    }
+                }
                 write!(f, ")")?;
                 let ret = sig.ret();
                 if *ret != Ty::unit() {
diff --git a/crates/ra_hir_ty/src/infer/expr.rs b/crates/ra_hir_ty/src/infer/expr.rs
index bd9a387f5..ab586b018 100644
--- a/crates/ra_hir_ty/src/infer/expr.rs
+++ b/crates/ra_hir_ty/src/infer/expr.rs
@@ -220,7 +220,7 @@ impl<'a> InferenceContext<'a> {
                 };
                 sig_tys.push(ret_ty.clone());
                 let sig_ty = Ty::apply(
-                    TypeCtor::FnPtr { num_args: sig_tys.len() as u16 - 1 },
+                    TypeCtor::FnPtr { num_args: sig_tys.len() as u16 - 1, is_varargs: false },
                     Substs(sig_tys.clone().into()),
                 );
                 let closure_ty =
diff --git a/crates/ra_hir_ty/src/lib.rs b/crates/ra_hir_ty/src/lib.rs
index d54568e67..c4c24a83b 100644
--- a/crates/ra_hir_ty/src/lib.rs
+++ b/crates/ra_hir_ty/src/lib.rs
@@ -112,7 +112,7 @@ pub enum TypeCtor {
     /// fn foo() -> i32 { 1 }
     /// let bar: fn() -> i32 = foo;
     /// ```
-    FnPtr { num_args: u16 },
+    FnPtr { num_args: u16, is_varargs: bool },
 
     /// The never type `!`.
     Never,
@@ -187,7 +187,7 @@ impl TypeCtor {
                     }
                 }
             }
-            TypeCtor::FnPtr { num_args } => num_args as usize + 1,
+            TypeCtor::FnPtr { num_args, is_varargs: _ } => num_args as usize + 1,
             TypeCtor::Tuple { cardinality } => cardinality as usize,
         }
     }
@@ -667,19 +667,20 @@ pub enum TyKind {
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct FnSig {
     params_and_return: Arc<[Ty]>,
+    is_varargs: bool,
 }
 
 /// A polymorphic function signature.
 pub type PolyFnSig = Binders<FnSig>;
 
 impl FnSig {
-    pub fn from_params_and_return(mut params: Vec<Ty>, ret: Ty) -> FnSig {
+    pub fn from_params_and_return(mut params: Vec<Ty>, ret: Ty, is_varargs: bool) -> FnSig {
         params.push(ret);
-        FnSig { params_and_return: params.into() }
+        FnSig { params_and_return: params.into(), is_varargs }
     }
 
-    pub fn from_fn_ptr_substs(substs: &Substs) -> FnSig {
-        FnSig { params_and_return: Arc::clone(&substs.0) }
+    pub fn from_fn_ptr_substs(substs: &Substs, is_varargs: bool) -> FnSig {
+        FnSig { params_and_return: Arc::clone(&substs.0), is_varargs }
     }
 
     pub fn params(&self) -> &[Ty] {
@@ -724,7 +725,7 @@ impl Ty {
     }
     pub fn fn_ptr(sig: FnSig) -> Self {
         Ty::apply(
-            TypeCtor::FnPtr { num_args: sig.params().len() as u16 },
+            TypeCtor::FnPtr { num_args: sig.params().len() as u16, is_varargs: sig.is_varargs },
             Substs(sig.params_and_return),
         )
     }
@@ -821,7 +822,9 @@ impl Ty {
     fn callable_sig(&self, db: &dyn 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 { is_varargs, .. } => {
+                    Some(FnSig::from_fn_ptr_substs(&a_ty.parameters, is_varargs))
+                }
                 TypeCtor::FnDef(def) => {
                     let sig = db.callable_item_signature(def);
                     Some(sig.subst(&a_ty.parameters))
diff --git a/crates/ra_hir_ty/src/lower.rs b/crates/ra_hir_ty/src/lower.rs
index 101b8aebe..6f4398e84 100644
--- a/crates/ra_hir_ty/src/lower.rs
+++ b/crates/ra_hir_ty/src/lower.rs
@@ -176,9 +176,12 @@ impl Ty {
                 Ty::apply_one(TypeCtor::Ref(*mutability), inner_ty)
             }
             TypeRef::Placeholder => Ty::Unknown,
-            TypeRef::Fn(params) => {
+            TypeRef::Fn(params, is_varargs) => {
                 let sig = Substs(params.iter().map(|tr| Ty::from_hir(ctx, tr)).collect());
-                Ty::apply(TypeCtor::FnPtr { num_args: sig.len() as u16 - 1 }, sig)
+                Ty::apply(
+                    TypeCtor::FnPtr { num_args: sig.len() as u16 - 1, is_varargs: *is_varargs },
+                    sig,
+                )
             }
             TypeRef::DynTrait(bounds) => {
                 let self_ty = Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0));
@@ -996,7 +999,7 @@ fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
     let ret = Ty::from_hir(&ctx_ret, &data.ret_type);
     let generics = generics(db.upcast(), def.into());
     let num_binders = generics.len();
-    Binders::new(num_binders, FnSig::from_params_and_return(params, ret))
+    Binders::new(num_binders, FnSig::from_params_and_return(params, ret, data.is_varargs))
 }
 
 /// Build the declared type of a function. This should not need to look at the
@@ -1047,7 +1050,7 @@ fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnS
     let params =
         fields.iter().map(|(_, field)| Ty::from_hir(&ctx, &field.type_ref)).collect::<Vec<_>>();
     let ret = type_for_adt(db, def.into());
-    Binders::new(ret.num_binders, FnSig::from_params_and_return(params, ret.value))
+    Binders::new(ret.num_binders, FnSig::from_params_and_return(params, ret.value, false))
 }
 
 /// Build the type of a tuple struct constructor.
@@ -1071,7 +1074,7 @@ fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId)
     let params =
         fields.iter().map(|(_, field)| Ty::from_hir(&ctx, &field.type_ref)).collect::<Vec<_>>();
     let ret = type_for_adt(db, def.parent.into());
-    Binders::new(ret.num_binders, FnSig::from_params_and_return(params, ret.value))
+    Binders::new(ret.num_binders, FnSig::from_params_and_return(params, ret.value, false))
 }
 
 /// Build the type of a tuple enum variant constructor.
diff --git a/crates/ra_hir_ty/src/traits/builtin.rs b/crates/ra_hir_ty/src/traits/builtin.rs
index 86e22e459..60cc9a9f5 100644
--- a/crates/ra_hir_ty/src/traits/builtin.rs
+++ b/crates/ra_hir_ty/src/traits/builtin.rs
@@ -121,7 +121,7 @@ fn closure_fn_trait_impl_datum(
             .build(),
     );
     let sig_ty = Ty::apply(
-        TypeCtor::FnPtr { num_args },
+        TypeCtor::FnPtr { num_args, is_varargs: false },
         Substs::builder(num_args as usize + 1)
             .fill_with_bound_vars(DebruijnIndex::INNERMOST, 0)
             .build(),
diff --git a/crates/ra_hir_ty/src/traits/chalk/mapping.rs b/crates/ra_hir_ty/src/traits/chalk/mapping.rs
index 06453ef82..5ba2ff51b 100644
--- a/crates/ra_hir_ty/src/traits/chalk/mapping.rs
+++ b/crates/ra_hir_ty/src/traits/chalk/mapping.rs
@@ -30,7 +30,7 @@ impl ToChalk for Ty {
             Ty::Apply(apply_ty) => match apply_ty.ctor {
                 TypeCtor::Ref(m) => ref_to_chalk(db, m, apply_ty.parameters),
                 TypeCtor::Array => array_to_chalk(db, apply_ty.parameters),
-                TypeCtor::FnPtr { num_args: _ } => {
+                TypeCtor::FnPtr { num_args: _, is_varargs: _ } => {
                     let substitution = apply_ty.parameters.to_chalk(db).shifted_in(&Interner);
                     chalk_ir::TyData::Function(chalk_ir::Fn { num_binders: 0, substitution })
                         .intern(&Interner)
@@ -124,7 +124,10 @@ impl ToChalk for Ty {
                     substitution.shifted_out(&Interner).expect("fn ptr should have no binders"),
                 );
                 Ty::Apply(ApplicationTy {
-                    ctor: TypeCtor::FnPtr { num_args: (parameters.len() - 1) as u16 },
+                    ctor: TypeCtor::FnPtr {
+                        num_args: (parameters.len() - 1) as u16,
+                        is_varargs: false,
+                    },
                     parameters,
                 })
             }