Add support for creating source ranges

pkg/analyzer_plugin/lib/utilities/range_factory.dart

Index: pkg/analyzer_plugin/lib/utilities/range_factory.dart
diff --git a/pkg/analyzer_plugin/lib/utilities/range_factory.dart b/pkg/analyzer_plugin/lib/utilities/range_factory.dart
new file mode 100644
index 0000000000000000000000000000000000000000..a875abf3f09f2d0c34b734ead7ddaf9024b68e70
--- /dev/null
+++ b/pkg/analyzer_plugin/lib/utilities/range_factory.dart
@@ -0,0 +1,118 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/syntactic_entity.dart';
+import 'package:analyzer/dart/ast/token.dart';
+import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/error/error.dart';
+import 'package:analyzer/src/generated/source.dart';
+
+/**
+ * An instance of [RangeFactory] made available for convenience.
+ */
+final RangeFactory range = new RangeFactory();
+
+/**
+ * A factory used to create instances of [SourceRange] based on various
+ * syntactic and semantic entities.
+ */
+class RangeFactory {
+  /**
+   * Return a source range that covers the name of the given [element].
+   */
+  SourceRange elementName(Element element) {
+    return new SourceRange(element.nameOffset, element.nameLength);
+  }
+
+  /**
+   * Return a source range that starts at the end of [leftEntity] and ends at
+   * the end of [rightEntity].
+   */
+  SourceRange endEnd(SyntacticEntity leftEntity, SyntacticEntity rightEntity) {
+    int offset = leftEntity.end;
+    int length = rightEntity.end - offset;
+    return new SourceRange(offset, length);
+  }
+
+  /**
+   * Return a source range that starts at the end of [entity] and has the given
+   * [length].
+   */
+  SourceRange endLength(SyntacticEntity entity, int length) {
+    return new SourceRange(entity.end, length);
+  }
+
+  /**
+   * Return a source range that starts at the end of [leftEntity] and ends at
+   * the start of [rightEntity].
+   */
+  SourceRange endStart(
+      SyntacticEntity leftEntity, SyntacticEntity rightEntity) {
+    int offset = leftEntity.end;
+    int length = rightEntity.offset - offset;
+    return new SourceRange(offset, length);
+  }
+
+  /**
+   * Return a source range that covers the same range as the given [error].
+   */
+  SourceRange error(AnalysisError error) {
+    return new SourceRange(error.offset, error.length);
+  }
+
+  /**
+   * Return a source range that covers the same range as the given [node].
+   */
+  SourceRange node(AstNode node) {
+    return new SourceRange(node.offset, node.length);
+  }
+
+  /**
+   * Return a source range that covers all of the given [nodes] (that is, from
+   * the start of the first node to the end of the last node.
+   */
+  SourceRange nodes(List<AstNode> nodes) {
+    if (nodes.isEmpty) {
+      return new SourceRange(0, 0);
+    }
+    return startEnd(nodes.first, nodes.last);
+  }
+
+  /**
+   * Return a source range that starts at the start of [leftEntity] and ends at
+   * the end of [rightEntity].
+   */
+  SourceRange startEnd(
+      SyntacticEntity leftEntity, SyntacticEntity rightEntity) {
+    int offset = leftEntity.offset;
+    int length = rightEntity.end - offset;
+    return new SourceRange(offset, length);
+  }
+
+  /**
+   * Return a source range that starts at the start of [entity] and has a length of [length].
+   */
+  SourceRange startLength(SyntacticEntity entity, int length) {
+    return new SourceRange(entity.offset, length);
+  }
+
+  /**
+   * Return a source range that starts at the start of [leftEntity] and ends at
+   * the start of [rightEntity].
+   */
+  SourceRange startStart(
+      SyntacticEntity leftEntity, SyntacticEntity rightEntity) {
+    int offset = leftEntity.offset;
+    int length = rightEntity.offset - offset;
+    return new SourceRange(offset, length);
+  }
+
+  /**
+   * Return a source range that covers the same range as the given [token].
+   */
+  SourceRange token(Token token) {
+    return new SourceRange(token.offset, token.length);
+  }
+}