forgot to update utils, there are a few new s

src/utils.rs

@@ -1,12 +1,42 @@
 use rustc::lint::Context;
-use syntax::codemap::ExpnInfo;
+use syntax::ast::{DefId, Name, Path};
+use syntax::codemap::{ExpnInfo, Span};
+use rustc::middle::ty;
 
+/// returns true if the macro that expanded the crate was outside of
+/// the current crate or was a compiler plugin
 pub fn in_macro(cx: &Context, opt_info: Option<&ExpnInfo>) -> bool {
+	// no ExpnInfo = no macro
 	opt_info.map_or(false, |info| {
+		// no span for the callee = external macro
 		info.callee.span.map_or(true, |span| {
+			// no snippet = external macro or compiler-builtin expansion
 			cx.sess().codemap().span_to_snippet(span).ok().map_or(true, |code| 
+				// macro doesn't start with "macro_rules"
+				// = compiler plugin
 				!code.starts_with("macro_rules")
 			)
 		})
 	})
 }
+
+/// invokes in_macro with the expansion info of the given span
+pub fn in_external_macro(cx: &Context, span: Span) -> bool {
+	cx.sess().codemap().with_expn_info(span.expn_id, 
+			|info| in_macro(cx, info))
+}
+
+/// check if a DefId's path matches the given absolute type path
+/// usage e.g. with
+/// `match_def_path(cx, id, &["core", "option", "Option"])`
+pub fn match_def_path(cx: &Context, def_id: DefId, path: &[&str]) -> bool {
+	ty::with_path(cx.tcx, def_id, |iter| iter.map(|elem| elem.name())
+		.zip(path.iter()).all(|(nm, p)| &nm.as_str() == p))
+}
+
+/// match a Path against a slice of segment string literals, e.g.
+/// `match_path(path, &["std", "rt", "begin_unwind"])`
+pub fn match_path(path: &Path, segments: &[&str]) -> bool {
+	path.segments.iter().rev().zip(segments.iter().rev()).all(
+		|(a,b)| a.identifier.as_str() == *b)
+}