Initial API for the Dart front_end package.

pkg/front_end/lib/source_span.dart

+// Copyright (c) 2016, 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.
+
+/// Defines the API for the front end to communicate information about source
+/// code locations to clients.
+library front_end.source_location;

[Brian Wilkerson, 2016/10/13 23:37:02]

If we're going to model source information differently than analyzer currently
does, is there a reason for not using the 'source_span' package
(https://pub.dartlang.org/packages/source_span)?

[Paul Berry, 2016/10/14 00:09:36]

I don't know.  I will investigate that package.

+
+/// A location in an input source file, possibly spanning several characters.
+class SourceSpan {

[Siggi Cherem (dart-lang), 2016/10/13 23:22:16]

it would be great if we could use SourceSpan from package:source_span
(https://www.dartdocs.org/documentation/source_span/1.2.3/).

It has a similar API, but also a lot of helper functions that already deal with
reporting error messages that can highlight line segments and such.

[Paul Berry, 2016/10/14 00:09:36]

Acknowledged.  I will investigate that package.

+  /// The Uri of the source file.
+  Uri get sourceUri;

[Brian Wilkerson, 2016/10/13 23:37:02]

I would suggest 'uri'; I think it's clear that this is the URI associated with
the source file.

[Paul Berry, 2016/10/14 00:09:36]

Fair enough.

+
+  /// The character offset from the beginning of the source file to the start of
+  /// the span.
+  int get offset;
+
+  /// The number of characters encompassed by the span.
+  int get length;
+
+  /// The line number of the start of the span (one-based).
+  int get startLine;
+
+  /// The character position of the start of the span (zero-based).
+  int get startChar;

[Brian Wilkerson, 2016/10/13 23:37:02]

I would suggest 'startColumn' (and 'endColumn') as being more clear.

[Paul Berry, 2016/10/14 00:09:36]

Sounds reasonable.

+
+  /// The line number of the end of the span (one-based).
+  int get endLine;
+
+  /// The character position of the end of the span (zero-based).
+  int get endChar;
+}