Remove a bunch of TODO(tall) and TODO(perf) comments that aren't needed.

lib/src/back_end/code_writer.dart

@@ -118,15 +118,11 @@ class CodeWriter {
   ///
   /// If [text] contains any internal newlines, the caller is responsible for
   /// also calling [handleNewline()].
+  ///
+  /// When possible, avoid calling this directly. Instead, any input code
+  /// lexemes should be written to TextPieces which then call this. That way,
+  /// selections inside lexemes are correctly updated.
   void write(String text) {
-    // TODO(tall): Calling this directly from pieces outside of TextPiece may
-    // not handle selections as gracefully as we could. A selection marker may
-    // get pushed past the text written here. Currently, this is only called
-    // directly for commas in list-like things, and `;` in for loops. In
-    // general, it's better for all text written to the output to live inside
-    // TextPieces because that will preserve selection markers. Consider doing
-    // something smarter for commas in lists and semicolons in for loops.
-
     _flushWhitespace();
     _buffer.write(text);
     _column += text.length;

lib/src/back_end/solution.dart

@@ -233,27 +233,11 @@ class Solution implements Comparable<Solution> {
     // end (or a winner).
     if (expandPiece == null) return const [];
 
-    // TODO(perf): If `_invalidPiece == expandPiece`, then we know that the
-    // first state leads to an invalid solution, so there's no point in trying
-    // to expand to a solution that binds `expandPiece` to
-    // `expandPiece.states[0]`. We should be able to do:
-    //
-    //     Iterable<State> states = expandPiece.states;
-    //     if (_invalidPiece == expandPiece) {
-    //       print('skip $expandPiece ${states.first}');
-    //       states = states.skip(1);
-    //     }
-    //
-    // And then use `states` below. But when I tried that, it didn't seem to
-    // make any noticeable performance difference on the one pathological
-    // example I tried. Leaving this here as a TODO to investigate more when
-    // there are other benchmarks we can try.
-    var solutions = <Solution>[];
-
     // For each state that the expanding piece can be in, create a new solution
     // that inherits all of the bindings of this one, and binds the expanding
     // piece to that state (along with any further pieces constrained by that
     // one).
+    var solutions = <Solution>[];
     for (var state in expandPiece.states) {
       var newStates = {..._pieceStates};
 

lib/src/front_end/ast_node_visitor.dart

@@ -520,9 +520,6 @@ class AstNodeVisitor extends ThrowingAstVisitor<void> with PieceFactory {
       if (node.members.isEmpty) {
         // If there are no members, format the constants like a delimited list.
         // This keeps the enum declaration on one line if it fits.
-        // TODO(tall): The old style preserves blank lines and newlines between
-        // enum values. A newline will also force the enum to split even if it
-        // would otherwise fit. Do we want to do that with the new style too?
         var builder =
             DelimitedListBuilder(this, const ListStyle(spaceWhenUnsplit: true));
 

lib/src/front_end/piece_writer.dart

@@ -302,8 +302,6 @@ class PieceWriter {
   void _flushSpace() {
     if (!_pendingSpace) return;
 
-    // TODO(perf): See if we can make SpacePiece a constant to avoid creating
-    // multiple.
     _pieces.last.add(SpacePiece());
     _pendingSpace = false;
   }

lib/src/piece/assign.dart

@@ -121,18 +121,6 @@ class AssignPiece extends Piece {
         _canBlockSplitLeft = canBlockSplitLeft,
         _canBlockSplitRight = canBlockSplitRight;
 
-  // TODO(tall): The old formatter allows the first operand of a split
-  // conditional expression to be on the same line as the `=`, as in:
-  //
-  //     var value = condition
-  //         ? thenValue
-  //         : elseValue;
-  //
-  // For now, we do not implement this special case behavior. Once more of the
-  // language is implemented in the new back end and we can run the formatter
-  // on a large corpus of code, we can try it out and see if the special case
-  // behavior is worth it.
-
   @override
   List<State> get additionalStates => [
         // If at least one operand can block split, allow splitting in operands

test/tall/invocation/chain_postfix.stmt

@@ -47,7 +47,6 @@ someReceiverObject.property1.property2
     .property5
     .property6;
 <<<
-### TODO(tall): Allow splitting between successive indexes.
 someReceiverObject
     .property1
     .property2