Support multiple occurrences of text in context

lib/src/utils.dart

Index: lib/src/utils.dart
diff --git a/lib/src/utils.dart b/lib/src/utils.dart
index 4a8eb551e5ca09a67c078a4e34a44719eb27bc64..d905188429474ee20bf627ed2dee696de7a88a47 100644
--- a/lib/src/utils.dart
+++ b/lib/src/utils.dart
@@ -37,3 +37,19 @@ int binarySearch(List list, bool matches(item)) {
   return max;
 }
 
+/// Finds a line in [context] containing [text] at the specified [column].
+///
+/// Returns the index in [context] where that line begins, or -1 if none exists.

[nweiz, 2015/03/31 19:22:10]

Nit: I really like using "null" as a signal for "not found" rather than "-1".
Granted it's inconsistent with String.indexOf, but it makes it a lot more
apparent when a caller fails to handle the case than an int.

[Siggi Cherem (dart-lang), 2015/03/31 19:51:21]

Done.

+int findLineStart(String context, String text, int column) {
+  var isEmpty = text == '';
+  var index = context.indexOf(text);
+  while (index != -1) {
+    var lineStart = context.lastIndexOf('\n', index) + 1;
+    var textColumn = index - lineStart;
+    if (column == textColumn || (isEmpty && column == textColumn + 1)) {
+      return lineStart;
+    }
+    index = context.indexOf(text, index + 1);
+  }
+  return -1;
+}