Use growable lists.

dart/sdk/lib/_internal/compiler/implementation/mirrors_used.dart

 // Copyright (c) 2013, 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.mirrors_used;
 
 import 'dart2jslib.dart' show
     Compiler,
     CompilerTask,
     Constant,
@@ skipping 437 matching lines @@
           return interface.asInstanceOf(supertype.element);
         }
       }
     }
     return type;
   }
 
   /// Ensure a list contains only strings.
   List<String> convertToListOfStrings(List list) {
     if (list == null) return null;
     List<String> result = new List<String>(list.length);

[karlklose, 2013/12/12 07:57:18]

Why not initialize result with '<String>[]' and then add the elements?

[ahe, 2013/12/12 09:58:07]

I know the size I need. I couldn't find any way to create a growable array with
a pre-allocated size.

[karlklose, 2013/12/12 10:27:49]

toList will create a new List and add the elements anyway, so this is not an
optimization.  I think the code reads better (and is faster), if you used the
literal and add.

[ahe, 2013/12/12 11:04:59]

That sounds like a performance bug in toList.

     int count = 0;
     for (var entry in list) {
       assert(invariant(spannable, entry is String));

[karlklose, 2013/12/12 07:57:18]

Why this invariant? Checked mode will already check the added element's type.

[ahe, 2013/12/12 09:58:07]

Checked mode doesn't know which AST node (or element) is causing the crash.
Also, checked mode allows null.

I think I can change this method to:

if (list == null) return null;
assert(invariant(spannable, list is List<String> && list is! List<int>));
assert(invariant(spannable, !list.contains(null));
return list;

Provided I also change convertConstantToUsageList to always return a
List<String>.

       result[count++] = entry;
     }
-    return result;
+    return result.toList(growable: true);

[karlklose, 2013/12/12 10:27:49]

'true' is the default.

[ahe, 2013/12/12 11:04:59]

Yes. But I'm passing the value explicitly to document that I want a growable
list.

   }
 
   /// Convert a list of strings and types to a list of elements. Types are
   /// converted to their corresponding element, and strings are resolved as
   /// follows:
   ///
   /// First find the longest library name that is a prefix of the string, if
   /// there are none, resolve using [resolveExpression]. Otherwise, resolve the
   /// rest of the string using [resolveLocalExpression].
   List<Element> resolveUsageList(List list) {
@@ skipping 116 matching lines @@
       // @MirrorsUsed(targets: fisk)
       //                       ^^^^
       //
       // Instead of saying 'fisk' should pretty print the problematic constant
       // value.
       return spannable;
     }
     return node;
   }
 }