Add Source.getTextLine and use it to display source snippets in error messages.

pkg/compiler/lib/src/io/source_map_builder.dart

 // Copyright (c) 2012, 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.
 
 library dart2js.source_map_builder;
 
+import 'package:kernel/ast.dart' show Location;
 import '../../compiler_new.dart' show OutputSink, OutputType;
 import '../util/uri_extras.dart' show relativize;
 import '../util/util.dart';
-import 'line_column_provider.dart';
+import 'location_provider.dart';
 import 'code_output.dart' show SourceLocationsProvider, SourceLocations;
 import 'source_information.dart' show SourceLocation;
 
 class SourceMapBuilder {
   final String version;
 
   /// The URI of the source map file.
   final Uri sourceMapUri;
 
   /// The URI of the target language file.
   final Uri targetFileUri;
 
-  final LineColumnProvider lineColumnProvider;
+  final LocationProvider locationProvider;
   final List<SourceMapEntry> entries = new List<SourceMapEntry>();
 
   SourceMapBuilder(this.version, this.sourceMapUri, this.targetFileUri,
-      this.lineColumnProvider);
+      this.locationProvider);
 
   void addMapping(int targetOffset, SourceLocation sourceLocation) {
     entries.add(new SourceMapEntry(sourceLocation, targetOffset));
   }
 
   void printStringListOn(Iterable<String> strings, StringBuffer buffer) {
     bool first = true;
     buffer.write('[');
     for (String string in strings) {
       if (!first) buffer.write(',');
       buffer.write('"');
       writeJsonEscapedCharsOn(string, buffer);
       buffer.write('"');
       first = false;
     }
     buffer.write(']');
   }
 
   String build() {
     LineColumnMap<SourceMapEntry> lineColumnMap =
         new LineColumnMap<SourceMapEntry>();
     Map<Uri, LineColumnMap<SourceMapEntry>> sourceLocationMap =
         <Uri, LineColumnMap<SourceMapEntry>>{};
     entries.forEach((SourceMapEntry sourceMapEntry) {
-      int line = lineColumnProvider.getLine(sourceMapEntry.targetOffset);
-      int column =
-          lineColumnProvider.getColumn(line, sourceMapEntry.targetOffset);
+      Location kernelLocation =
+          locationProvider.getLocation(sourceMapEntry.targetOffset);
+      int line = kernelLocation.line - 1;
+      int column = kernelLocation.column - 1;
       lineColumnMap.add(line, column, sourceMapEntry);
 
       SourceLocation location = sourceMapEntry.sourceLocation;
       if (location != null) {
         if (location.sourceUri != null) {
           LineColumnMap<SourceMapEntry> sourceLineColumnMap =
               sourceLocationMap.putIfAbsent(location.sourceUri,
                   () => new LineColumnMap<SourceMapEntry>());
           sourceLineColumnMap.add(
               location.line, location.column, sourceMapEntry);
@@ skipping 110 matching lines @@
       String sourceMapFileName = relativize(fileUri, sourceMapUri, false);
       return '''
 
 //# sourceMappingURL=$sourceMapFileName
 ''';
     }
     return '';
   }
 
   /// Generates source map files for all [SourceLocations] in
-  /// [sourceLocationsProvider] for the .js code in [lineColumnProvider]
+  /// [sourceLocationsProvider] for the .js code in [locationProvider]
   /// [sourceMapUri] is used to relativizes the URIs of the referenced source
   /// files and the target [fileUri]. [name] and [outputProvider] are used to
   /// create the [OutputSink] for the source map text.
   static void outputSourceMap(
       SourceLocationsProvider sourceLocationsProvider,
-      LineColumnProvider lineColumnProvider,
+      LocationProvider locationProvider,
       String name,
       Uri sourceMapUri,
       Uri fileUri,
       OutputSink outputProvider(
           String name, String extension, OutputType type)) {
     // Create a source file for the compilation output. This allows using
     // [:getLine:] to transform offsets to line numbers in [SourceMapBuilder].
     int index = 0;
     sourceLocationsProvider.sourceLocations
         .forEach((SourceLocations sourceLocations) {
       SourceMapBuilder sourceMapBuilder = new SourceMapBuilder(
-          sourceLocations.name, sourceMapUri, fileUri, lineColumnProvider);
+          sourceLocations.name, sourceMapUri, fileUri, locationProvider);
       sourceLocations.forEachSourceLocation(sourceMapBuilder.addMapping);
       String sourceMap = sourceMapBuilder.build();
       String extension = 'js.map';
       if (index > 0) {
         if (name == '') {
           name = fileUri != null ? fileUri.pathSegments.last : 'out.js';
           extension = 'map.${sourceLocations.name}';
         } else {
           extension = 'js.map.${sourceLocations.name}';
         }
@@ skipping 140 matching lines @@
   int register(T element) {
     return map.putIfAbsent(element, () => map.length);
   }
 
   /// Returns the index of [element].
   int operator [](T element) => map[element];
 
   /// Returns the indexed elements.
   Iterable<T> get elements => map.keys;
 }