diff --git a/clippy_lints/src/zero_sized_map_values.rs b/clippy_lints/src/zero_sized_map_values.rs
index 22d008de758a..19405df77f75 100644
--- a/clippy_lints/src/zero_sized_map_values.rs
+++ b/clippy_lints/src/zero_sized_map_values.rs
@@ -16,8 +16,9 @@ declare_clippy_lint! {
     /// containing zero sized values is effectively a set. Using a set in that case improves
     /// readability and communicates intent more clearly.
     ///
-    /// **Known problems:** A zero-sized type cannot be recovered later if it contains private
-    /// fields.
+    /// **Known problems:**
+    /// * A zero-sized type cannot be recovered later if it contains private fields.
+    /// * This lints the signature of public items
     ///
     /// **Example:**
     ///
@@ -33,7 +34,7 @@ declare_clippy_lint! {
     /// }
     /// ```
     pub ZERO_SIZED_MAP_VALUES,
-    nursery,
+    pedantic,
     "usage of map with zero-sized value type"
 }
 
@@ -46,107 +47,35 @@ impl LateLintPass<'_> for ZeroSizedMapValues {
         self.check_ty(cx, ty, local.pat.span);
     }
 
-    fn check_fn(&mut self, cx: &LateContext<'_>, _: FnKind<'_>, decl: &FnDecl<'_>, _: &Body<'_>, _: Span, id: HirId) {
-        if let Some(Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_item(id)) {
+    fn check_ty(&mut self, cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>) {
+        let parent_id = cx.tcx.hir().get_parent_item(hir_ty.hir_id);
+        if let Some(Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_item(parent_id)) {
             if let ItemKind::Impl { of_trait: Some(_), .. } = item.kind {
                 return;
             }
         }
 
-        self.check_fn_decl(cx, decl);
-    }
-
-    fn check_struct_field(&mut self, cx: &LateContext<'_>, field: &StructField<'_>) {
-        self.check_hir_ty(cx, field.ty);
-    }
-
-    fn check_trait_item(&mut self, cx: &LateContext<'_>, item: &TraitItem<'_>) {
-        match item.kind {
-            TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => {
-                self.check_hir_ty(cx, ty);
-            },
-            TraitItemKind::Fn(ref sig, _) => {
-                self.check_fn_decl(cx, &sig.decl);
-            },
-            _ => (),
-        }
-    }
-}
-
-impl ZeroSizedMapValues {
-    fn check_fn_decl(&mut self, cx: &LateContext<'_>, decl: &FnDecl<'_>) {
-        for ty in decl.inputs {
-            self.check_hir_ty(cx, ty);
-        }
-
-        if let FnRetTy::Return(ty) = decl.output {
-            self.check_hir_ty(cx, ty);
-        }
-    }
-
-    fn check_hir_ty(&mut self, cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>) {
+        // TODO this causes errors in some cases
         let ty = hir_ty_to_ty(cx.tcx, hir_ty);
         self.check_ty(cx, ty, hir_ty.span);
-
-        match hir_ty.kind {
-            TyKind::Path(ref qpath) => match *qpath {
-                QPath::Resolved(ty, ref p) => {
-                    if let Some(ty) = ty {
-                        self.check_hir_ty(cx, ty);
-                    }
-
-                    for ty in p.segments.iter().flat_map(|seg| {
-                        seg.args
-                            .as_ref()
-                            .map_or_else(|| [].iter(), |params| params.args.iter())
-                            .filter_map(|arg| match arg {
-                                GenericArg::Type(ty) => Some(ty),
-                                _ => None,
-                            })
-                    }) {
-                        self.check_hir_ty(cx, ty);
-                    }
-                },
-                QPath::TypeRelative(ty, ref seg) => {
-                    self.check_hir_ty(cx, ty);
-
-                    if let Some(ref params) = seg.args {
-                        for ty in params.args.iter().filter_map(|arg| match arg {
-                            GenericArg::Type(ty) => Some(ty),
-                            _ => None,
-                        }) {
-                            self.check_hir_ty(cx, ty);
-                        }
-                    }
-                },
-                QPath::LangItem(..) => {},
-            },
-            TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
-                self.check_hir_ty(cx, ty);
-            },
-            TyKind::Tup(tys) => {
-                for ty in tys {
-                    self.check_hir_ty(cx, ty);
-                }
-            },
-            _ => {},
-        }
     }
+}
 
+impl ZeroSizedMapValues {
     fn check_ty<'tcx>(&mut self, cx: &LateContext<'tcx>, ty: Ty<'tcx>, span: Span) {
         if span.from_expansion() {
             return;
         }
 
         if_chain! {
-                if match_type(cx, ty, &paths::HASHMAP) || match_type(cx, ty, &paths::BTREEMAP);
-                if let Adt(_, ref substs) = ty.kind();
-                let ty = substs.type_at(1);
-                if let Ok(layout) = cx.layout_of(ty);
-                if layout.is_zst();
-                then {
-                    span_lint_and_help(cx, ZERO_SIZED_MAP_VALUES, span, "map with zero-sized value type", None, "consider using a set instead");
-                }
+            if match_type(cx, ty, &paths::HASHMAP) || match_type(cx, ty, &paths::BTREEMAP);
+            if let Adt(_, ref substs) = ty.kind();
+            let ty = substs.type_at(1);
+            if let Ok(layout) = cx.layout_of(ty);
+            if layout.is_zst();
+            then {
+                span_lint_and_help(cx, ZERO_SIZED_MAP_VALUES, span, "map with zero-sized value type", None, "consider using a set instead");
+            }
         }
     }
 }