Handle index expressions in the middle of call chains.

lib/src/source_visitor.dart

Index: lib/src/source_visitor.dart
diff --git a/lib/src/source_visitor.dart b/lib/src/source_visitor.dart
index 42e2fc61c3a6daccad8601f6401c1e11a58ba2aa..ba3ba5e08e688ffa463738598c740ec65a897c5f 100644
--- a/lib/src/source_visitor.dart
+++ b/lib/src/source_visitor.dart
@@ -1012,8 +1012,18 @@ class SourceVisitor implements AstVisitor {
       visit(node.target);
     }
 
+    finishIndexExpression(node);
+
+    builder.unnest();
+  }
+
+  /// Visit the index part of [node], excluding the target.
+  ///
+  /// Called by [CallChainVisitor] to handle index expressions in the middle of
+  /// call chains.
+  void finishIndexExpression(IndexExpression node) {
     if (node.target is IndexExpression) {
-      // Corner case: On a chain of [] accesses, allow splitting between them.
+      // Edge case: On a chain of [] accesses, allow splitting between them.
       // Produces nicer output in cases like:
       //
       //     someJson['property']['property']['property']['property']...
@@ -1026,7 +1036,6 @@ class SourceVisitor implements AstVisitor {
     visit(node.index);
     token(node.rightBracket);
     builder.endSpan();
-    builder.unnest();
   }
 
   visitInstanceCreationExpression(InstanceCreationExpression node) {