Source positions for constructors and lots of async machinery

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 730d5605b16b7a2f2cfa1bd21d8272a3950a61e1..a345676176403bcea18a039a3b0aa18c0801e879 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -2694,7 +2694,7 @@ RawFunction* Function::CreateMethodExtractor(const String& getter_name) const {
                   false,  // Not external.
                   false,  // Not native.
                   owner,
-                  0));    // token_pos
+                  ClassifyingTokenPositions::kMethodExtractor));  // token_pos
 
   // Initialize signature: receiver is a single fixed parameter.
   const intptr_t kNumParameters = 1;
@@ -5787,7 +5787,7 @@ void Function::set_recognized_kind(MethodRecognizer::Kind value) const {
 
 
 void Function::set_token_pos(intptr_t token_pos) const {
-  ASSERT(token_pos >= 0);
+  ASSERT((token_pos >= 0) || IsMethodExtractor());
   StoreNonPointer(&raw_ptr()->token_pos_, token_pos);
 }
 
@@ -8547,7 +8547,10 @@ TokenStream::Iterator::Iterator(const TokenStream& tokens,
       cur_token_kind_(Token::kILLEGAL),
       cur_token_obj_index_(-1),
       stream_type_(stream_type) {
-  SetCurrentPosition(token_pos);
+  ASSERT(token_pos != Scanner::kNoSourcePos);
+  if (token_pos >= 0) {
+    SetCurrentPosition(token_pos);
+  }
 }