WIP [esnext] implement async iteration proposal

src/builtins/builtins.h

Index: src/builtins/builtins.h
diff --git a/src/builtins/builtins.h b/src/builtins/builtins.h
index dcff15068f83275b86dea74085b89feff6cda0c2..4a833ea6302064c32a0d4582eb3470f197af0c55 100644
--- a/src/builtins/builtins.h
+++ b/src/builtins/builtins.h
@@ -119,6 +119,7 @@ namespace internal {
   ASM(JSEntryTrampoline)                                                       \
   ASM(JSConstructEntryTrampoline)                                              \
   ASM(ResumeGeneratorTrampoline)                                               \
+  ASM(ResumeAwaitedGeneratorTrampoline)                                        \
                                                                                \
   /* Stack and interrupt check */                                              \
   ASM(InterruptCheck)                                                          \
@@ -771,7 +772,46 @@ namespace internal {
   /* ES6 #sec-%typedarray%.prototype.keys */                                   \
   TFJ(TypedArrayPrototypeKeys, 0)                                              \
   /* ES6 #sec-%typedarray%.prototype.values */                                 \
-  TFJ(TypedArrayPrototypeValues, 0)
+  TFJ(TypedArrayPrototypeValues, 0)                                            \
+                                                                               \
+  /* AsyncGenerator builtins */                                                \
+                                                                               \
+  /* AsyncGeneratorFunction( p1, p2, ... pn, body ) */                         \
+  /* proposal-async-iteration/#sec-asyncgeneratorfunction-constructor */       \
+  CPP(AsyncGeneratorFunctionConstructor)                                       \
+  /* AsyncGenerator.prototype.next ( value ) */                                \
+  /* proposal-async-iteration/#sec-asyncgenerator-prototype-next */            \
+  TFJ(AsyncGeneratorPrototypeNext, 1)                                          \
+  /* AsyncGenerator.prototype.return ( value ) */                              \
+  /* proposal-async-iteration/#sec-asyncgenerator-prototype-return */          \
+  TFJ(AsyncGeneratorPrototypeReturn, 1)                                        \
+  /* AsyncGenerator.prototype.throw ( exception ) */                           \
+  /* proposal-async-iteration/#sec-asyncgenerator-prototype-throw */           \
+  TFJ(AsyncGeneratorPrototypeThrow, 1)                                         \
+                                                                               \
+  /* Await (proposal-async-iteration/#await), with resume behaviour */         \
+  /* specific to Async Generators. Internal / Not exposed to JS code. */       \
+  TFJ(AsyncGeneratorAwaitCaught, 2)                                            \
+  TFJ(AsyncGeneratorAwaitUncaught, 2)                                          \
+  TFJ(AsyncGeneratorAwaitResolveClosure, 1)                                    \
+  TFJ(AsyncGeneratorAwaitRejectClosure, 1)                                     \
+                                                                               \
+  /* GeneratorYield (proposal-async-iteration/#sec-generatoryield) with */     \
+  /* resume behaviour specific to Async Generators. Internal / not exposed */  \
+  /* to JS code. */                                                            \
+  TFJ(AsyncGeneratorYield, 1)                                                  \
+  TFJ(AsyncGeneratorRawYield, 1)                                               \
+                                                                               \
+  /* Async-from-Sync Iterator builtins */                                      \
+                                                                               \
+  /* %AsyncFromSyncIteratorPrototype% */                                       \
+  /* (proposal-async-iteration/#sec-%asyncfromsynciteratorprototype%-object)*/ \
+  TFJ(AsyncFromSyncIteratorPrototypeNext, 1)                                   \
+  TFJ(AsyncFromSyncIteratorPrototypeThrow, 1)                                  \
+  TFJ(AsyncFromSyncIteratorPrototypeReturn, 1)                                 \
+                                                                               \
+  /* proposal-async-iteration/#sec-async-iterator-value-unwrap-functions */    \
+  TFJ(AsyncIteratorValueUnwrap, 1)
 
 #define IGNORE_BUILTIN(...)