fix false positive len_zero in is_empty()

src/utils.rs

@@ -2,7 +2,7 @@ use rustc::lint::*;
 use rustc_front::hir::*;
 use reexport::*;
 use syntax::codemap::{ExpnInfo, Span, ExpnFormat};
-use rustc::front::map::Node::NodeExpr;
+use rustc::front::map::Node::*;
 use rustc::middle::def_id::DefId;
 use rustc::middle::ty;
 use std::borrow::Cow;
@@ -100,6 +100,19 @@ pub fn match_path(path: &Path, segments: &[&str]) -> bool {
         |(a, b)| &a.identifier.name == b)
 }
 
+pub fn with_item_name<T, F>(cx: &Context, expr: &Expr, f: F) -> Option<T>
+where F: FnOnce(Name) -> T {
+    let parent_id = cx.tcx.map.get_parent(expr.id);
+    match cx.tcx.map.find(parent_id) {
+        Some(NodeItem(&Item{ ref ident, .. })) |
+        Some(NodeTraitItem(&TraitItem{ id: _, ref ident, .. })) |
+        Some(NodeImplItem(&ImplItem{ id: _, ref ident, .. })) => {
+            Some(f(ident.name))
+        },
+        _ => None,
+    }
+}
+
 /// convert a span to a code snippet if available, otherwise use default, e.g.
 /// `snippet(cx, expr.span, "..")`
 pub fn snippet<'a>(cx: &Context, span: Span, default: &'a str) -> Cow<'a, str> {