Add convenience getter to extract the location of an AST node.

lib/ast.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.
 
 /// -----------------------------------------------------------------------
 ///                           ERROR HANDLING
 /// -----------------------------------------------------------------------
 ///
 /// As a rule of thumb, errors that can be detected statically are handled by
 /// the frontend, typically by translating the erroneous code into a 'throw' or
@@ skipping 116 matching lines @@
   }
 
   /// Removes this node from the [List] it is currently stored in, or assigns
   /// `null` to the field on the parent currently pointing to the node.
   ///
   /// Has no effect if the node is orphaned or if the parent pointer is stale.
   void remove() {
     parent?.replaceChild(this, null);
     parent = null;
   }
+
+  Program get enclosingProgram => parent?.enclosingProgram;
+
+  /// Returns the best known source location of the given AST node, or `null` if
+  /// the node is orphaned.
+  ///
+  /// This getter is intended for diagnostics and debugging, and should be
+  /// avoided in production code.
+  Location get location {
+    if (fileOffset == noOffset) return parent?.location;
+    return _getLocationInEnclosingFile(fileOffset);
+  }
+
+  Location _getLocationInEnclosingFile(int offset) {
+    return parent?._getLocationInEnclosingFile(offset);
+  }
 }
 
 // ------------------------------------------------------------------------
 //                      LIBRARIES and CLASSES
 // ------------------------------------------------------------------------
 
 class Library extends TreeNode implements Comparable<Library> {
   /// An absolute import path to this library.
   ///
   /// The [Uri] should have the `dart`, `package`, or `file` scheme.
@@ skipping 70 matching lines @@
   }
 
   static int _libraryIdCounter = 0;
   int _libraryId = ++_libraryIdCounter;
 
   int compareTo(Library other) => _libraryId - other._libraryId;
 
   /// Returns a possibly synthesized name for this library, consistent with
   /// the names across all [toString] calls.
   String toString() => debugLibraryName(this);
+
+  Location _getLocationInEnclosingFile(int offset) {
+    return enclosingProgram.getLocation(fileUri, offset);
+  }
 }
 
 /// The degree to which the contents of a class have been loaded into memory.
 ///
 /// Each level imply the requirements of the previous ones.
 enum ClassLevel {
   /// Temporary loading level for internal use by IR producers.  Consumers of
   /// kernel code should not expect to see classes at this level.
   Temporary,
 
@@ skipping 214 matching lines @@
       supertype = v.visitSupertype(supertype);
     }
     if (mixedInType != null) {
       mixedInType = v.visitSupertype(mixedInType);
     }
     transformSupertypeList(implementedTypes, v);
     transformList(constructors, v, this);
     transformList(procedures, v, this);
     transformList(fields, v, this);
   }
+
+  Location _getLocationInEnclosingFile(int offset) {
+    return enclosingProgram.getLocation(fileUri, offset);
+  }
 }
 
 // ------------------------------------------------------------------------
 //                            MEMBERS
 // ------------------------------------------------------------------------
 
 /// A indirect reference to a member, which can be updated to point at another
 /// member at a later time.
 class _MemberAccessor {
   Member target;
@@ skipping 248 matching lines @@
   ///
   /// [DirectPropertySet] and [FieldInitializer]s are not affected, and will
   /// continue to access the field directly.  [PropertySet] nodes created after
   /// the call will not be affected until the method is called again.
   ///
   /// Existing [ClassHierarchy] instances are not affected by this call.
   void replaceSetterInterfaceWith(Procedure setter) {
     _setterInterface.target = setter;
     _setterInterface = new _MemberAccessor(this);
   }
+
+  Location _getLocationInEnclosingFile(int offset) {
+    return enclosingProgram.getLocation(fileUri, offset);
+  }
 }
 
 /// A generative constructor, possibly redirecting.
 ///
 /// Note that factory constructors are treated as [Procedure]s.
 ///
 /// Constructors do not take type parameters.  Type arguments from a constructor
 /// invocation should be matched with the type parameters declared in the class.
 ///
 /// For unnamed constructors, the name is an empty string (in a [Name]).
@@ skipping 2752 matching lines @@
   accept(TreeVisitor v) => v.visitProgram(this);
 
   visitChildren(Visitor v) {
     visitList(libraries, v);
     mainMethod?.acceptReference(v);
   }
 
   transformChildren(Transformer v) {
     transformList(libraries, v, this);
   }
+
+  Program get enclosingProgram => this;
+
+  /// Translates an offset to line and column numbers in the given file.
+  Location getLocation(String file, int offset) {
+    List<int> lines = uriToLineStarts[file];
+    int low = 0, high = lines.length - 1;
+    while (low < high) {
+      int mid = high - ((high - low) >> 1); // Get middle, rounding up.
+      int pivot = lines[mid];
+      if (pivot <= offset) {
+        low = mid;
+      } else {
+        high = mid - 1;
+      }
+    }
+    int lineIndex = low;
+    int lineStart = lines[lineIndex];
+    int lineNumber = 1 + lineIndex;
+    int columnNumber = offset - lineStart;
+    return new Location(file, lineNumber, columnNumber);
+  }
+}
+
+/// A tuple with file, line, and column number, for displaying human-readable

[ahe, 2016/10/25 14:43:35]

(and Emacs-readable)

Nice touch :-)

+/// locations.
+class Location {
+  final String file;
+  final int line; // 1-based.
+  final int column; // 1-based.
+
+  Location(this.file, this.line, this.column);
+
+  String toString() => '$file:$line:$column';
 }
 
 // ------------------------------------------------------------------------
 //                             INTERNAL FUNCTIONS
 // ------------------------------------------------------------------------
 
 void setParents(List<TreeNode> nodes, TreeNode parent) {
   for (int i = 0; i < nodes.length; ++i) {
     nodes[i].parent = parent;
   }
@@ skipping 69 matching lines @@
 
   @override
   defaultTreeNode(TreeNode node) {
     if (node == child) {
       return replacement;
     } else {
       return node;
     }
   }
 }