Await it!

runtime/vm/parser.cc

 // Copyright (c) 2012, 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.
 
 #include "vm/parser.h"
 
 #include "lib/invocation_mirror.h"
 #include "platform/utils.h"
 #include "vm/ast_transformer.h"
 #include "vm/bootstrap.h"
@@ skipping 5407 matching lines @@
                                   current_block_->scope->function_level() + 1,
                                   0);
   }
   ChainNewBlock(outer_scope);
 }
 
 
 void Parser::OpenAsyncClosure() {
   TRACE_PARSER("OpenAsyncClosure");
   parsed_function()->set_await_temps_scope(current_block_->scope);
-  // TODO(mlippautz): Set up explicit jump table for await continuations.
 }
 
 
 RawFunction* Parser::OpenAsyncFunction(intptr_t formal_param_pos) {
   TRACE_PARSER("OpenAsyncFunction");
   // Create the closure containing the old body of this function.
   Class& sig_cls = Class::ZoneHandle(I);
   Type& sig_type = Type::ZoneHandle(I);
   Function& closure = Function::ZoneHandle(I);
   String& sig = String::ZoneHandle(I);
@@ skipping 55 matching lines @@
   TRACE_PARSER("CloseAsyncFunction");
   ASSERT(!closure.IsNull());
   ASSERT(closure_body != NULL);
   // The block for the async closure body has already been closed. Close the
   // corresponding function block.
   CloseBlock();
 
   // Create and return a new future that executes a closure with the current
   // body.
 
-  bool found = false;
-
   // No need to capture parameters or other variables, since they have already
   // been captured in the corresponding scope as the body has been parsed within
   // a nested block (contained in the async funtion's block).
   const Class& future = Class::ZoneHandle(I,
       GetClassForAsync(Symbols::Future()));
   ASSERT(!future.IsNull());
   const Function& constructor = Function::ZoneHandle(I,
       future.LookupFunction(Symbols::FutureConstructor()));
   ASSERT(!constructor.IsNull());
   const Class& completer = Class::ZoneHandle(I,
       GetClassForAsync(Symbols::Completer()));
   ASSERT(!completer.IsNull());
   const Function& completer_constructor = Function::ZoneHandle(I,
       completer.LookupFunction(Symbols::CompleterConstructor()));
   ASSERT(!completer_constructor.IsNull());
 
+  bool found = false;
   // Add to AST:
   //   var :async_op;
   //   var :async_completer;
+  //   var :await_jump_var;
+  //   var :await_ctx_var;
+  // Add as many variables to saved the try block ctx as there were try blocks.
+  //   var :await_saved_try_ctx_var_<x>;

[hausner, 2014/08/25 20:26:14]

is the name :await_saved_try_ctx_var_ or :async_saved_try_ctx_var_?

[Michael Lippautz (Google), 2014/08/26 16:45:48]

Done. Using :async_... 

+  Type& dynamic_type = Type::ZoneHandle(I, Type::DynamicType());

[hausner, 2014/08/25 20:26:14]

const

[Michael Lippautz (Google), 2014/08/26 16:45:48]

Done.

   LocalVariable* async_op_var = new (I) LocalVariable(
-      Scanner::kNoSourcePos,
-      Symbols::AsyncOperation(),
-      Type::ZoneHandle(I, Type::DynamicType()));
+      Scanner::kNoSourcePos, Symbols::AsyncOperation(), dynamic_type);
   current_block_->scope->AddVariable(async_op_var);
   found = closure_body->scope()->CaptureVariable(Symbols::AsyncOperation());
   ASSERT(found);
   LocalVariable* async_completer = new (I) LocalVariable(
-      Scanner::kNoSourcePos,
-      Symbols::AsyncCompleter(),
-      Type::ZoneHandle(I, Type::DynamicType()));
+      Scanner::kNoSourcePos, Symbols::AsyncCompleter(), dynamic_type);
   current_block_->scope->AddVariable(async_completer);
   found = closure_body->scope()->CaptureVariable(Symbols::AsyncCompleter());
   ASSERT(found);
+  LocalVariable* await_jump_var = new (I) LocalVariable(
+      Scanner::kNoSourcePos, Symbols::AwaitJumpVar(), dynamic_type);
+  current_block_->scope->AddVariable(await_jump_var);
+  found = closure_body->scope()->CaptureVariable(Symbols::AwaitJumpVar());
+  ASSERT(found);
+  LocalVariable* await_ctx_var = new (I) LocalVariable(
+      Scanner::kNoSourcePos, Symbols::AwaitContextVar(), dynamic_type);
+  current_block_->scope->AddVariable(await_ctx_var);
+  found = closure_body->scope()->CaptureVariable(Symbols::AwaitContextVar());
+  ASSERT(found);
+  LocalVariable* async_saved_try_ctx_var;
+  const char* async_saved_prefix = ":async_saved_try_ctx_var_";
+  for (int16_t i = 0; i < last_used_try_index_; i++) {
+    const String& cnt_str = String::ZoneHandle(

[hausner, 2014/08/25 20:26:14]

cnt_str can be a regular handle, need not be a zone handle.

Also, the code pattern of building a string or symbol from this prefix and a
given integer appears in 3 places. Maybe you can factor it out into a short
static inline function with parameters isolate and index. 

[Michael Lippautz (Google), 2014/08/26 16:45:48]

Done: BuildAsyncSavedTryContextName()

+        I, String::NewFormatted("%s%d", async_saved_prefix, i));
+    const String& symbol = String::ZoneHandle(I, Symbols::New(cnt_str));
+    async_saved_try_ctx_var = new (I) LocalVariable(
+        Scanner::kNoSourcePos, symbol, dynamic_type);
+    current_block_->scope->AddVariable(async_saved_try_ctx_var);
+    found = closure_body->scope()->CaptureVariable(symbol);
+    ASSERT(found);
+  }
 
   // Add to AST:
   //   :async_completer = new Completer();
-  ArgumentListNode* empty_args = new (I) ArgumentListNode(
-      Scanner::kNoSourcePos);
+  ArgumentListNode* empty_args =
+      new (I) ArgumentListNode(Scanner::kNoSourcePos);
   ConstructorCallNode* completer_constructor_node = new (I) ConstructorCallNode(
       Scanner::kNoSourcePos,
       TypeArguments::ZoneHandle(I),
       completer_constructor,
       empty_args);
   StoreLocalNode* store_completer = new (I) StoreLocalNode(
       Scanner::kNoSourcePos,
       async_completer,
       completer_constructor_node);
   current_block_->statements->Add(store_completer);
@@ skipping 30 matching lines @@
           Symbols::CompleterFuture()));
   current_block_->statements->Add(return_node);
   return CloseBlock();
 }
 
 
 void Parser::CloseAsyncClosure(SequenceNode* body) {
   TRACE_PARSER("CloseAsyncClosure");
   // We need a temporary expression to store intermediate return values.
   parsed_function()->EnsureExpressionTemp();
+  // Implicitly mark those variables below as captured. We currently mark all
+  // variables of all scopes as captured (below), but as soon as we do something
+  // smarter we rely on these internal variables to be available.
+  body->scope()->LookupVariable(Symbols::Completer(), false);
+  body->scope()->LookupVariable(Symbols::AwaitJumpVar(), false);
+  body->scope()->LookupVariable(Symbols::AwaitContextVar(), false);
+  body->scope()->RecursivelyCaptureAllVariables();
 }
 
 
 // Set up default values for all optional parameters to the function.
 void Parser::SetupDefaultsForOptionalParams(const ParamList* params,
                                             Array* default_values) {
   if (params->num_optional_parameters > 0) {
     // Build array of default parameter values.
     ParamDesc* param =
       params->parameters->data() + params->num_fixed_parameters;
@@ skipping 1514 matching lines @@
        }
     stack_trace_param->var = var;
   }
 }
 
 
 SequenceNode* Parser::ParseFinallyBlock() {
   TRACE_PARSER("ParseFinallyBlock");
   OpenBlock();
   ExpectToken(Token::kLBRACE);
+
+  // In case of async closures we need to restore the saved try index of an
+  // outer try block (if it exists).  The current try block has already been
+  // removed from the stack of try blocks.
+  if (current_function().is_async_closure() && (try_blocks_list_ != NULL)) {
+    // We need two unchain two scopes: finally clause, and the try block level.
+    SetupSavedTryContext(current_block_->scope->parent()->parent(),
+                         try_blocks_list_->try_index(),
+                         current_block_->statements);
+  } else {
+    parsed_function()->reset_saved_try_ctx_vars();
+  }
+
   ParseStatementSequence();
   ExpectToken(Token::kRBRACE);
   SequenceNode* finally_block = CloseBlock();
   return finally_block;
 }
 
 
 void Parser::PushTryBlock(Block* try_block) {
   intptr_t try_index = AllocateTryIndex();
   TryBlocks* block = new(I) TryBlocks(
@@ skipping 125 matching lines @@
       current_block_->statements->Add(new(I) InstanceCallNode(
           catch_pos,
           new(I) LoadLocalNode(catch_pos, stack_trace_param.var),
           Library::PrivateCoreLibName(Symbols::_setupFullStackTrace()),
           no_args));
     }
 
     // Add nested block with user-defined code.  This blocks allows
     // declarations in the body to shadow the catch parameters.
     CheckToken(Token::kLBRACE);
+
+    // In case of async closures we need to restore the saved try index of an
+    // outer try block (if it exists).
+    ASSERT(try_blocks_list_ != NULL);
+    if (current_function().is_async_closure() &&
+        (try_blocks_list_->outer_try_block() != NULL)) {
+      // We need to unchain three scope levels: catch clause, catch parameters,
+      // and the general try block.
+      SetupSavedTryContext(current_block_->scope->parent()->parent()->parent(),
+                           try_blocks_list_->outer_try_block()->try_index(),
+                           current_block_->statements);
+    } else {
+      parsed_function()->reset_saved_try_ctx_vars();
+    }
+
     current_block_->statements->Add(ParseNestedStatement(false, NULL));
     catch_blocks.Add(CloseBlock());
 
     const bool is_bad_type =
         exception_param.type->IsMalformed() ||
         exception_param.type->IsMalbounded();
     if (exception_param.type->IsDynamicType() || is_bad_type) {
       // There is no exception type or else it is malformed or malbounded.
       // In the first case, unconditionally execute the catch body.  In the
       // second case, unconditionally throw.
@@ skipping 74 matching lines @@
   while (!type_tests.is_empty()) {
     AstNode* type_test = type_tests.RemoveLast();
     SequenceNode* catch_block = catch_blocks.RemoveLast();
     current_block_->statements->Add(new(I) IfNode(
         type_test->token_pos(), type_test, catch_block, current));
     current = CloseBlock();
   }
   return current;
 }
 
 

[hausner, 2014/08/25 20:26:14]

Could you add a short comment describing what this helper function does?

[Michael Lippautz (Google), 2014/08/26 16:45:48]

Done.

+void Parser::SetupSavedTryContext(LocalScope* saved_try_context_scope,
+                                  int16_t try_index,
+                                  SequenceNode* target) {
+  LocalVariable* saved_try_ctx = saved_try_context_scope->LookupVariable(
+      Symbols::SavedTryContextVar(), false);
+  ASSERT((saved_try_ctx != NULL) && !saved_try_ctx->is_captured());
+  const char* async_saved_prefix = ":async_saved_try_ctx_var_";
+  const String& cnt_str = String::ZoneHandle(

[hausner, 2014/08/25 20:26:14]

cnt_str probably doesn't need to be a ZoneHandle; a regular Handle is
sufficient.

[Michael Lippautz (Google), 2014/08/26 16:45:48]

Done.

+      I, String::NewFormatted("%s%d", async_saved_prefix, try_index));
+  const String& current_await_saved_try_ctx_symbol = String::ZoneHandle(
+      I, Symbols::New(cnt_str));
+  LocalVariable* async_saved_try_ctx =
+      target->scope()->LookupVariable(
+          current_await_saved_try_ctx_symbol, false);
+  ASSERT((async_saved_try_ctx != NULL) && async_saved_try_ctx->is_captured());
+  target->Add(new (I) StoreLocalNode(
+      Scanner::kNoSourcePos, saved_try_ctx, new (I) LoadLocalNode(
+          Scanner::kNoSourcePos, async_saved_try_ctx)));
+
+  parsed_function()->set_saved_try_ctx(saved_try_ctx);
+  parsed_function()->set_async_saved_try_ctx(async_saved_try_ctx);
+}
+
+
 AstNode* Parser::ParseTryStatement(String* label_name) {
   TRACE_PARSER("ParseTryStatement");
 
   // We create three variables for exceptions here:
   // ':saved_try_context_var' - Used to save the context before the start of
   //                            the try block. The context register is
   //                            restored from this variable before
   //                            processing the catch block handler.
   // ':exception_var' - Used to save the current exception object that was
   //                    thrown.
@@ skipping 38 matching lines @@
   if (label_name != NULL) {
     try_label = SourceLabel::New(try_pos, label_name, SourceLabel::kStatement);
     OpenBlock();
     current_block_->scope->AddLabel(try_label);
   }
 
   // Now parse the 'try' block.
   OpenBlock();
   PushTryBlock(current_block_);
   ExpectToken(Token::kLBRACE);
+
+  const char* async_saved_prefix = ":async_saved_try_ctx_var_";
+  if (current_function().is_async_closure()) {
+    const String& cnt_str = String::ZoneHandle(

[srdjan, 2014/08/26 15:54:33]

Regular handle: use ZoneHandle-s only if the variable escapes its scope.

[Michael Lippautz (Google), 2014/08/26 16:45:48]

Done. Code is now refactored but uses a regular handle for constructing the
string.

+        I, String::NewFormatted("%s%d",
+            async_saved_prefix, last_used_try_index_-1));
+    const String& current_await_saved_try_ctx_symbol =
+        String::ZoneHandle(I, Symbols::New(cnt_str));
+    LocalVariable* async_saved_try_ctx =
+        current_block_->scope->LookupVariable(
+            current_await_saved_try_ctx_symbol, false);
+    ASSERT(async_saved_try_ctx != NULL);
+    ASSERT(context_var);
+    current_block_->statements->Add(new (I) StoreLocalNode(
+        Scanner::kNoSourcePos, async_saved_try_ctx, new (I) LoadLocalNode(
+            Scanner::kNoSourcePos, context_var)));
+    parsed_function()->set_saved_try_ctx(context_var);
+    parsed_function()->set_async_saved_try_ctx(async_saved_try_ctx);
+  }
+
   ParseStatementSequence();
   ExpectToken(Token::kRBRACE);
   SequenceNode* try_block = CloseBlock();
 
   if ((CurrentToken() != Token::kCATCH) && !IsLiteral("on") &&
       (CurrentToken() != Token::kFINALLY)) {
     ReportError("catch or finally clause expected");
   }
 
   // Now parse the 'catch' blocks if any.
@@ skipping 52 matching lines @@
   // and attach the label to it.
   AstNode* try_catch_node = new(I) TryCatchNode(
       try_pos, try_block, context_var, catch_clause, finally_block, try_index);
 
   if (try_label != NULL) {
     current_block_->statements->Add(try_catch_node);
     SequenceNode* sequence = CloseBlock();
     sequence->set_label(try_label);
     try_catch_node = sequence;
   }
+
+  // In case of async closures we need to restore the saved try index of an
+  // outer try block (if it exists).
+  if (current_function().is_async_closure() &&
+      (outer_try_index != CatchClauseNode::kInvalidTryIndex)) {
+    SequenceNode* try_catch_and_restore_try_ctx = new (I) SequenceNode(
+        Scanner::kNoSourcePos, current_block_->scope);
+    try_catch_and_restore_try_ctx->Add(try_catch_node);
+    SetupSavedTryContext(
+        current_block_->scope, outer_try_index, try_catch_and_restore_try_ctx);
+    return try_catch_and_restore_try_ctx;
+  } else {
+    parsed_function()->reset_saved_try_ctx_vars();
+  }
+
   return try_catch_node;
 }
 
 
 AstNode* Parser::ParseJump(String* label_name) {
   TRACE_PARSER("ParseJump");
   ASSERT(CurrentToken() == Token::kBREAK || CurrentToken() == Token::kCONTINUE);
   Token::Kind jump_kind = CurrentToken();
   const intptr_t jump_pos = TokenPos();
   SourceLabel* target = NULL;
@@ skipping 3758 matching lines @@
 void Parser::SkipQualIdent() {
   ASSERT(IsIdentifier());
   ConsumeToken();
   if (CurrentToken() == Token::kPERIOD) {
     ConsumeToken();  // Consume the kPERIOD token.
     ExpectIdentifier("identifier expected after '.'");
   }
 }
 
 }  // namespace dart