Fix source information positions for deserialized patched elements.

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

Index: pkg/compiler/lib/src/io/source_information.dart
diff --git a/pkg/compiler/lib/src/io/source_information.dart b/pkg/compiler/lib/src/io/source_information.dart
index cf3872cd0e35f229c23db196461c2f062247b6ad..a84d8bfe55077ba296029051e1fa237ade3d80b2 100644
--- a/pkg/compiler/lib/src/io/source_information.dart
+++ b/pkg/compiler/lib/src/io/source_information.dart
@@ -5,8 +5,15 @@
 library dart2js.source_information;
 
 import '../common.dart';
-import '../elements/elements.dart' show AstElement, LocalElement, ResolvedAst;
+import '../elements/elements.dart'
+    show
+        AstElement,
+        CompilationUnitElement,
+        LocalElement,
+        ResolvedAst,
+        ResolvedAstKind;
 import '../js/js.dart' show JavaScriptNodeSourceInformation;
+import '../script.dart';
 import '../tree/tree.dart' show Node;
 import 'source_file.dart';
 
@@ -37,8 +44,8 @@ abstract class SourceInformation extends JavaScriptNodeSourceInformation {
 class SourceInformationStrategy {
   const SourceInformationStrategy();
 
-  /// Create a [SourceInformationBuilder] for [element].
-  SourceInformationBuilder createBuilderForContext(AstElement element) {
+  /// Create a [SourceInformationBuilder] for [resolvedAst].
+  SourceInformationBuilder createBuilderForContext(ResolvedAst resolvedAst) {
     return const SourceInformationBuilder();
   }
 
@@ -53,8 +60,8 @@ class SourceInformationStrategy {
 class SourceInformationBuilder {
   const SourceInformationBuilder();
 
-  /// Create a [SourceInformationBuilder] for [element].
-  SourceInformationBuilder forContext(AstElement element) => this;
+  /// Create a [SourceInformationBuilder] for [resolvedAst].
+  SourceInformationBuilder forContext(ResolvedAst resolvedAst) => this;
 
   /// Generate [SourceInformation] the declaration of the element in
   /// [resolvedAst].
@@ -151,7 +158,9 @@ abstract class SourceLocation {
   int _line;
 
   SourceLocation(this._sourceFile) {
-    assert(isValid);
+    assert(invariant(new SourceSpan(sourceUri, 0, 0), isValid,
+        message: "Invalid source location in ${sourceUri}: "
+            "offset=$offset, length=${_sourceFile.length}."));
   }
 
   /// The absolute URI of the source file of this source location.
@@ -244,3 +253,32 @@ String computeElementNameForSourceMaps(AstElement element) {
     return element.name;
   }
 }
+
+/// Computes the [SourceFile] for the source code of [resolvedAst].
+SourceFile computeSourceFile(ResolvedAst resolvedAst) {
+  SourceFile sourceFile;
+  if (resolvedAst.kind != ResolvedAstKind.PARSED) {
+    // Synthesized node. Use the enclosing element for the location.
+    sourceFile = resolvedAst.element.compilationUnit.script.file;
+  } else {
+    Uri uri = resolvedAst.sourceUri;
+    AstElement implementation = resolvedAst.element.implementation;
+    Script script = implementation.compilationUnit.script;
+    if (uri == script.resourceUri) {
+      sourceFile = script.file;
+    } else {
+      // Slow path, happens only for deserialized elements.
+      // TODO(johnniwinther): Support a way to get a [SourceFile] from a
+      // [Uri].
+      for (CompilationUnitElement compilationUnit
+          in implementation.library.compilationUnits) {
+        Script script = compilationUnit.script;
+        if (uri == script.resourceUri) {
+          sourceFile = script.file;
+          break;
+        }
+      }
+    }
+  }
+  return sourceFile;
+}