5 files changed, 86 insertions, 35 deletions

diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index 0f6953158..859bdfb3b 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -1233,9 +1233,13 @@ impl Type {
     }
 
     pub fn as_callable(&self, db: &dyn HirDatabase) -> Option<Callable> {
-        let (id, substs) = self.ty.value.as_callable()?;
-        let sig = db.callable_item_signature(id).subst(substs);
-        Some(Callable { ty: self.clone(), sig, id, is_bound_method: false })
+        let def = match self.ty.value {
+            Ty::Apply(ApplicationTy { ctor: TypeCtor::FnDef(def), parameters: _ }) => Some(def),
+            _ => None,
+        };
+
+        let sig = self.ty.value.callable_sig(db)?;
+        Some(Callable { ty: self.clone(), sig, def, is_bound_method: false })
     }
 
     pub fn is_closure(&self) -> bool {
@@ -1525,7 +1529,7 @@ impl HirDisplay for Type {
 pub struct Callable {
     ty: Type,
     sig: FnSig,
-    id: CallableDefId,
+    def: Option<CallableDefId>,
     pub(crate) is_bound_method: bool,
 }
 
@@ -1533,19 +1537,21 @@ pub enum CallableKind {
     Function(Function),
     TupleStruct(Struct),
     TupleEnumVariant(EnumVariant),
+    Closure,
 }
 
 impl Callable {
     pub fn kind(&self) -> CallableKind {
-        match self.id {
-            CallableDefId::FunctionId(it) => CallableKind::Function(it.into()),
-            CallableDefId::StructId(it) => CallableKind::TupleStruct(it.into()),
-            CallableDefId::EnumVariantId(it) => CallableKind::TupleEnumVariant(it.into()),
+        match self.def {
+            Some(CallableDefId::FunctionId(it)) => CallableKind::Function(it.into()),
+            Some(CallableDefId::StructId(it)) => CallableKind::TupleStruct(it.into()),
+            Some(CallableDefId::EnumVariantId(it)) => CallableKind::TupleEnumVariant(it.into()),
+            None => CallableKind::Closure,
         }
     }
     pub fn receiver_param(&self, db: &dyn HirDatabase) -> Option<ast::SelfParam> {
-        let func = match self.id {
-            CallableDefId::FunctionId(it) if self.is_bound_method => it,
+        let func = match self.def {
+            Some(CallableDefId::FunctionId(it)) if self.is_bound_method => it,
             _ => return None,
         };
         let src = func.lookup(db.upcast()).source(db.upcast());
@@ -1565,8 +1571,8 @@ impl Callable {
             .iter()
             .skip(if self.is_bound_method { 1 } else { 0 })
             .map(|ty| self.ty.derived(ty.clone()));
-        let patterns = match self.id {
-            CallableDefId::FunctionId(func) => {
+        let patterns = match self.def {
+            Some(CallableDefId::FunctionId(func)) => {
                 let src = func.lookup(db.upcast()).source(db.upcast());
                 src.value.param_list().map(|param_list| {
                     param_list
@@ -1577,8 +1583,7 @@ impl Callable {
                         .chain(param_list.params().map(|it| it.pat().map(Either::Right)))
                 })
             }
-            CallableDefId::StructId(_) => None,
-            CallableDefId::EnumVariantId(_) => None,
+            _ => None,
         };
         patterns.into_iter().flatten().chain(iter::repeat(None)).zip(types).collect()
     }
diff --git a/crates/ra_hir_ty/src/diagnostics/expr.rs b/crates/ra_hir_ty/src/diagnostics/expr.rs
index 557d01cdc..fd930eab1 100644
--- a/crates/ra_hir_ty/src/diagnostics/expr.rs
+++ b/crates/ra_hir_ty/src/diagnostics/expr.rs
@@ -158,28 +158,32 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
         }
 
         let is_method_call = matches!(expr, Expr::MethodCall { .. });
-        let (callee, args) = match expr {
+        let (sig, args) = match expr {
             Expr::Call { callee, args } => {
                 let callee = &self.infer.type_of_expr[*callee];
-                let (callable, _) = callee.as_callable()?;
-
-                (callable, args.clone())
+                let sig = callee.callable_sig(db)?;
+                (sig, args.clone())
             }
             Expr::MethodCall { receiver, args, .. } => {
-                let callee = self.infer.method_resolution(call_id)?;
                 let mut args = args.clone();
                 args.insert(0, *receiver);
-                (callee.into(), args)
+
+                // FIXME: note that we erase information about substs here. This
+                // is not right, but, luckily, doesn't matter as we care only
+                // about the number of params
+                let callee = self.infer.method_resolution(call_id)?;
+                let sig = db.callable_item_signature(callee.into()).value;
+
+                (sig, args)
             }
             _ => return None,
         };
 
-        let sig = db.callable_item_signature(callee);
-        if sig.value.is_varargs {
+        if sig.is_varargs {
             return None;
         }
 
-        let params = sig.value.params();
+        let params = sig.params();
 
         let mut param_count = params.len();
         let mut arg_count = args.len();
@@ -542,4 +546,20 @@ fn f() {
         "#,
         )
     }
+
+    #[test]
+    fn arg_count_lambda() {
+        check_diagnostics(
+            r#"
+fn main() {
+    let f = |()| ();
+    f();
+  //^^^ Expected 1 argument, found 0
+    f(());
+    f((), ());
+  //^^^^^^^^^ Expected 1 argument, found 2
+}
+"#,
+        )
+    }
 }
diff --git a/crates/ra_hir_ty/src/lib.rs b/crates/ra_hir_ty/src/lib.rs
index 0ef5ca78f..7698cb0d4 100644
--- a/crates/ra_hir_ty/src/lib.rs
+++ b/crates/ra_hir_ty/src/lib.rs
@@ -767,15 +767,6 @@ impl Ty {
         }
     }
 
-    pub fn as_callable(&self) -> Option<(CallableDefId, &Substs)> {
-        match self {
-            Ty::Apply(ApplicationTy { ctor: TypeCtor::FnDef(callable_def), parameters }) => {
-                Some((*callable_def, parameters))
-            }
-            _ => None,
-        }
-    }
-
     pub fn is_never(&self) -> bool {
         matches!(self, Ty::Apply(ApplicationTy { ctor: TypeCtor::Never, .. }))
     }
@@ -807,7 +798,7 @@ impl Ty {
         }
     }
 
-    fn callable_sig(&self, db: &dyn HirDatabase) -> Option<FnSig> {
+    pub fn callable_sig(&self, db: &dyn HirDatabase) -> Option<FnSig> {
         match self {
             Ty::Apply(a_ty) => match a_ty.ctor {
                 TypeCtor::FnPtr { is_varargs, .. } => {
diff --git a/crates/ra_ide/src/call_info.rs b/crates/ra_ide/src/call_info.rs
index 35a8a0dc5..14980afdd 100644
--- a/crates/ra_ide/src/call_info.rs
+++ b/crates/ra_ide/src/call_info.rs
@@ -70,6 +70,7 @@ pub(crate) fn call_info(db: &RootDatabase, position: FilePosition) -> Option<Cal
                 variant.name(db)
             );
         }
+        hir::CallableKind::Closure => (),
     }
 
     res.signature.push('(');
@@ -93,7 +94,7 @@ pub(crate) fn call_info(db: &RootDatabase, position: FilePosition) -> Option<Cal
     res.signature.push(')');
 
     match callable.kind() {
-        hir::CallableKind::Function(_) => {
+        hir::CallableKind::Function(_) | hir::CallableKind::Closure => {
             let ret_type = callable.return_type();
             if !ret_type.is_unit() {
                 format_to!(res.signature, " -> {}", ret_type.display(db));
@@ -702,4 +703,36 @@ id! {
             "#]],
         );
     }
+
+    #[test]
+    fn call_info_for_lambdas() {
+        check(
+            r#"
+struct S;
+fn foo(s: S) -> i32 { 92 }
+fn main() {
+    (|s| foo(s))(<|>)
+}
+        "#,
+            expect![[r#"
+                (S) -> i32
+                (<S>)
+            "#]],
+        )
+    }
+
+    #[test]
+    fn call_info_for_fn_ptr() {
+        check(
+            r#"
+fn main(f: fn(i32, f64) -> char) {
+    f(0, <|>)
+}
+        "#,
+            expect![[r#"
+                (i32, f64) -> char
+                (i32, <f64>)
+            "#]],
+        )
+    }
 }
diff --git a/crates/ra_ide/src/inlay_hints.rs b/crates/ra_ide/src/inlay_hints.rs
index cec3b04e8..43a5e29b5 100644
--- a/crates/ra_ide/src/inlay_hints.rs
+++ b/crates/ra_ide/src/inlay_hints.rs
@@ -262,7 +262,9 @@ fn should_show_param_name_hint(
     let param_name = param_name.trim_start_matches('_');
     let fn_name = match callable.kind() {
         hir::CallableKind::Function(it) => Some(it.name(sema.db).to_string()),
-        hir::CallableKind::TupleStruct(_) | hir::CallableKind::TupleEnumVariant(_) => None,
+        hir::CallableKind::TupleStruct(_)
+        | hir::CallableKind::TupleEnumVariant(_)
+        | hir::CallableKind::Closure => None,
     };
     if param_name.is_empty()
         || Some(param_name) == fn_name.as_ref().map(|s| s.trim_start_matches('_'))