[kernel] Debugging of switch statement

runtime/vm/kernel_binary.cc

 // 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.
 #if !defined(DART_PRECOMPILED_RUNTIME)
 
 #include "platform/globals.h"
 #include "vm/flags.h"
 #include "vm/growable_array.h"
 #include "vm/kernel.h"
 #include "vm/kernel_to_il.h"
@@ skipping 1577 matching lines @@
     SwitchCase* sc = stmt->cases_[i];
     sc->ReadFrom(reader);
   }
   return stmt;
 }
 
 
 SwitchCase* SwitchCase::ReadFrom(Reader* reader) {
   TRACE_READ_OFFSET();
   expressions_.ReadFromStatic<Expression>(reader);
+  // List of expression offsets of same length as expressions_: This serves as

[Kevin Millikin (Google), 2017/03/20 12:29:47]

I think it's obvious that it serves as the positions of the expression.  And
it's equally useful in all cases.  Don't editorialize too much in comments.

If you think it's confusing and needs a remark, you could say that we wouldn't
need this if all constant expressions had a position.

[jensj, 2017/03/21 10:06:19]

Comment removed.

+  // positions of the expressions, especially useful if the expressions
+  // doesn't have a position (e.g. int literal).
+  int length = reader->ReadListLength();
+  for (intptr_t i = 0; i < length; ++i) {
+    expressions_[i]->set_position(reader->ReadPosition());
+  }
   is_default_ = reader->ReadBool();
   body_ = Statement::ReadFrom(reader);
   return this;
 }
 
 
 ContinueSwitchStatement* ContinueSwitchStatement::ReadFrom(Reader* reader) {
   TRACE_READ_OFFSET();
   ContinueSwitchStatement* stmt = new ContinueSwitchStatement();
   stmt->target_ = reader->helper()->switch_cases().Lookup(reader->ReadUInt());
@@ skipping 324 matching lines @@
 
 kernel::Program* ReadPrecompiledKernelFromBuffer(const uint8_t* buffer,
                                                  intptr_t buffer_length) {
   kernel::Reader reader(buffer, buffer_length);
   return kernel::Program::ReadFrom(&reader);
 }
 
 
 }  // namespace dart
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)