Factor out parsing of various types of rules.

errors.rs

@@ -0,0 +1,26 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use cssparser::{SyntaxError, SourceLocation};
+
+
+pub struct ErrorLoggerIterator<I>(I);
+
+impl<T, I: Iterator<Result<T, SyntaxError>>> Iterator<T> for ErrorLoggerIterator<I> {
+    pub fn next(&mut self) -> Option<T> {
+        for result in **self {
+            match result {
+                Ok(v) => return Some(v),
+                Err(error) => log_css_error(error.location, fmt!("%?", error.reason))
+            }
+        }
+        None
+    }
+}
+
+
+pub fn log_css_error(location: SourceLocation, message: &str) {
+    // TODO eventually this will got into a "web console" or something.
+    info!("%u:%u %s", location.line, location.column, message)
+}