Move NameFilter to its own file so it can be conveniently reused.

pkg/analyzer/lib/src/summary/prelink.dart

Index: pkg/analyzer/lib/src/summary/prelink.dart
diff --git a/pkg/analyzer/lib/src/summary/prelink.dart b/pkg/analyzer/lib/src/summary/prelink.dart
index 5a1cc93d8880a486143c16c5b628fa46ac174a5e..bfa20ca561ca292e9fad6bbda2d5a1172ba68219 100644
--- a/pkg/analyzer/lib/src/summary/prelink.dart
+++ b/pkg/analyzer/lib/src/summary/prelink.dart
@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer/src/summary/format.dart';
+import 'package:analyzer/src/summary/name_filter.dart';
 
 /**
  * Create a [PrelinkedLibraryBuilder] corresponding to the given
@@ -40,95 +41,6 @@ typedef UnlinkedPublicNamespace GetImportCallback(String relativeUri);
 typedef UnlinkedUnit GetPartCallback(String relativeUri);
 
 /**
- * A [NameFilter] represents the set of filtering rules implied by zero or more
- * combinators in an `export` or `import` statement.
- */
-class NameFilter {
-  /**
-   * A [NameFilter] representing no filtering at all (i.e. no combinators).
-   */
-  static final NameFilter identity =
-      new NameFilter._(hiddenNames: new Set<String>());
-
-  /**
-   * If this [NameFilter] accepts a finite number of names and hides all
-   * others, the (possibly empty) set of names it accepts.  Otherwise `null`.
-   */
-  final Set<String> shownNames;
-
-  /**
-   * If [shownNames] is `null`, the (possibly empty) set of names not accepted
-   * by this filter (all other names are accepted).  If [shownNames] is not
-   * `null`, then [hiddenNames] will be `null`.
-   */
-  final Set<String> hiddenNames;
-
-  /**
-   * Create a [NameFilter] based on the given [combinator].
-   */
-  factory NameFilter.forCombinator(UnlinkedCombinator combinator) {
-    if (combinator.shows.isNotEmpty) {
-      return new NameFilter._(shownNames: combinator.shows.toSet());
-    } else {
-      return new NameFilter._(hiddenNames: combinator.hides.toSet());
-    }
-  }
-
-  /**
-   * Create a [NameFilter] based on the given (possibly empty) sequence of
-   * [combinators].
-   */
-  factory NameFilter.forCombinators(List<UnlinkedCombinator> combinators) {
-    NameFilter result = identity;
-    for (UnlinkedCombinator combinator in combinators) {
-      result = result.merge(new NameFilter.forCombinator(combinator));
-    }
-    return result;
-  }
-
-  const NameFilter._({this.shownNames, this.hiddenNames});
-
-  /**
-   * Determine if the given [name] is accepted by this [NameFilter].
-   */
-  bool accepts(String name) {
-    if (name.endsWith('=')) {
-      name = name.substring(0, name.length - 1);
-    }
-    if (shownNames != null) {
-      return shownNames.contains(name);
-    } else {
-      return !hiddenNames.contains(name);
-    }
-  }
-
-  /**
-   * Produce a new [NameFilter] by combining this [NameFilter] with another
-   * one.  The new [NameFilter] will only accept names that would be accepted
-   * by both input filters.
-   */
-  NameFilter merge(NameFilter other) {
-    if (shownNames != null) {
-      if (other.shownNames != null) {
-        return new NameFilter._(
-            shownNames: shownNames.intersection(other.shownNames));
-      } else {
-        return new NameFilter._(
-            shownNames: shownNames.difference(other.hiddenNames));
-      }
-    } else {
-      if (other.shownNames != null) {
-        return new NameFilter._(
-            shownNames: other.shownNames.difference(hiddenNames));
-      } else {
-        return new NameFilter._(
-            hiddenNames: hiddenNames.union(other.hiddenNames));
-      }
-    }
-  }
-}
-
-/**
  * A [_Meaning] stores all the information necessary to find the declaration
  * referred to by a name in a namespace.
  */
@@ -290,7 +202,8 @@ class _Prelinker {
               }
             });
             chaseExports(
-                filter.merge(new NameFilter.forCombinators(export.combinators)),
+                filter.merge(
+                    new NameFilter.forUnlinkedCombinators(export.combinators)),
                 exportUri,
                 seenUris);
           }
@@ -347,7 +260,7 @@ class _Prelinker {
   void filterExportNamespace(String relativeUri,
       List<UnlinkedCombinator> combinators, Map<String, _Meaning> result) {
     Map<String, _Meaning> exportNamespace = computeExportNamespace(relativeUri);
-    NameFilter filter = new NameFilter.forCombinators(combinators);
+    NameFilter filter = new NameFilter.forUnlinkedCombinators(combinators);
     exportNamespace.forEach((String name, _Meaning meaning) {
       if (filter.accepts(name) && !result.containsKey(name)) {
         result[name] = meaning;