Fix incorrect identifiers.

lib/src/functions.dart

Index: lib/src/functions.dart
diff --git a/lib/src/functions.dart b/lib/src/functions.dart
index 7f3ff9981b19d63af3e121af6fe6344cf9249956..9c973b8aede3a69286ff6ea9ef68f7bc9d360867 100644
--- a/lib/src/functions.dart
+++ b/lib/src/functions.dart
@@ -75,7 +75,7 @@ Map<dynamic/*=T*/, List/*<S>*/> groupBy/*<S, T>*/(Iterable/*<S>*/ values,
       minOrderBy = elementOrderBy;
     }
   }
-  return min;
+  return minValue;
 }
 
 /// Returns the element of [values] for which [orderBy] returns the maximum
@@ -97,7 +97,7 @@ Map<dynamic/*=T*/, List/*<S>*/> groupBy/*<S, T>*/(Iterable/*<S>*/ values,
       maxOrderBy = elementOrderBy;
     }
   }
-  return max;
+  return maxValue;
 }
 
 /// Returns the [transitive closure][] of [graph].