Validate that Trace.from's argument isn't null.
R=rnystrom@google.com
BUG=16071
Review URL: https://codereview.chromium.org//137443002
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/stack_trace@31762 260f80e4-7a28-3924-810f-c04153c831b5
diff --git a/pkgs/stack_trace/lib/src/trace.dart b/pkgs/stack_trace/lib/src/trace.dart
index 21e8afc..c1d751f 100644
--- a/pkgs/stack_trace/lib/src/trace.dart
+++ b/pkgs/stack_trace/lib/src/trace.dart
@@ -92,6 +92,13 @@
/// If [trace] is a native [StackTrace], its data will be parsed out; if it's
/// a [Trace], it will be returned as-is.
factory Trace.from(StackTrace trace) {
+ // Normally explicitly validating null arguments is bad Dart style, but here
+ // the natural failure will only occur when the LazyTrace is materialized,
+ // and we want to provide an error that's more local to the actual problem.
+ if (trace == null) {
+ throw new ArgumentError("Cannot create a Trace from null.");
+ }
+
if (trace is Trace) return trace;
if (trace is Chain) return trace.toTrace();
return new LazyTrace(() => new Trace.parse(trace.toString()));
