Implement parsing support for generic functions

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 "vm/flags.h"
 
 #ifndef DART_PRECOMPILED_RUNTIME
 
 #include "lib/invocation_mirror.h"
@@ skipping 30 matching lines @@
 
 namespace dart {
 
 DEFINE_FLAG(bool, enable_debug_break, false, "Allow use of break \"message\".");
 DEFINE_FLAG(bool, trace_parser, false, "Trace parser operations.");
 DEFINE_FLAG(bool, warn_mixin_typedef, true, "Warning on legacy mixin typedef.");
 // TODO(floitsch): remove the conditional-directive flag, once we publicly
 // committed to the current version.
 DEFINE_FLAG(bool, conditional_directives, true,
     "Enable conditional directives");
+DEFINE_FLAG(bool, generic_method_syntax, false, "Enbable generic functions.");

[siva, 2016/08/19 23:08:13]

s/Enbable/Enable/

[hausner, 2016/08/19 23:12:01]

Done. I was clearly babbling.

 DEFINE_FLAG(bool, initializing_formal_access, false,
     "Make initializing formal parameters visible in initializer list.");
 DEFINE_FLAG(bool, warn_super, false,
     "Warning if super initializer not last in initializer list.");
 DEFINE_FLAG(bool, warn_patch, false, "Warn on old-style patch syntax.");
 DEFINE_FLAG(bool, await_is_keyword, false,
     "await and yield are treated as proper keywords in synchronous code.");
 
 DECLARE_FLAG(bool, profile_vm);
 DECLARE_FLAG(bool, trace_service);
@@ skipping 57 matching lines @@
   ~BoolScope() {
     *_addr = _saved_value;
   }
 
  private:
   bool* _addr;
   bool _saved_value;
 };
 
 
+// Helper class to save and restore token position.
+class Parser::TokenPosScope : public ValueObject {
+ public:
+  explicit TokenPosScope(Parser *p) : p_(p) {
+    saved_pos_ = p_->TokenPos();
+  }
+  TokenPosScope(Parser *p, TokenPosition pos) : p_(p), saved_pos_(pos) {
+  }
+  ~TokenPosScope() {
+    p_->SetPosition(saved_pos_);
+  }
+
+ private:
+  Parser* p_;
+  TokenPosition saved_pos_;
+  DISALLOW_COPY_AND_ASSIGN(TokenPosScope);
+};
+
+
 class RecursionChecker : public ValueObject {
  public:
   explicit RecursionChecker(Parser* p) : parser_(p) {
     parser_->recursion_counter_++;
     // No need to check the stack unless the parser is in an unusually deep
     // recurive state. Thus, we omit the more expensive stack checks in
     // the common case.
     const int kMaxUncheckedDepth = 100;  // Somewhat arbitrary.
     if (parser_->recursion_counter_ > kMaxUncheckedDepth) {
       parser_->CheckStack();
@@ skipping 1920 matching lines @@
   const intptr_t num_existing_parameters =
       params->num_fixed_parameters + params->num_optional_parameters;
   for (intptr_t i = 0; i < num_existing_parameters; i++) {
     ParamDesc& existing_parameter = (*params->parameters)[i];
     if (existing_parameter.name->Equals(*parameter.name)) {
       ReportError(parameter.name_pos, "duplicate formal parameter '%s'",
                   parameter.name->ToCString());
     }
   }
 
-  if (CurrentToken() == Token::kLPAREN) {
+  if (IsParameterPart()) {
     // This parameter is probably a closure. If we saw the keyword 'var'
     // or 'final', a closure is not legal here and we ignore the
     // opening parens.
     // TODO(hausner): The language spec appears to allow var and final
     // in signature types when used with initializing formals:
     // fieldFormalParameter:
     // metadata finalConstVarOrType? this ‘.’ identifier formalParameterList? ;
     if (!var_seen && !final_seen) {
       // The parsed parameter type is actually the function result type.
       const AbstractType& result_type =
           AbstractType::Handle(Z, parameter.type->raw());
 
       // Finish parsing the function type parameter.
+      if (CurrentToken() == Token::kLT) {
+        // TODO(hausner): handle generic function types.
+        if (!FLAG_generic_method_syntax) {
+          ReportError("generic function types not supported");
+        }
+        TokenPosition type_param_pos = TokenPos();
+        if (!TryParseTypeParameters()) {
+          ReportError(type_param_pos, "error in type parameters");
+        }
+      }
+
+      ASSERT(CurrentToken() == Token::kLPAREN);
       ParamList func_params;
 
       // Add implicit closure object parameter.
       func_params.AddFinalParameter(
           TokenPos(),
           &Symbols::ClosureParameter(),
           &Object::dynamic_type());
 
       const bool no_explicit_default_values = false;
       ParseFormalParameterList(no_explicit_default_values, false, &func_params);
@@ skipping 1617 matching lines @@
 
   // We have a name that is not shadowed, followed by a period or #.
   // Consume the identifier, let the caller consume the . or #.
   ConsumeToken();
   return prefix.raw();
 }
 
 
 void Parser::ParseMethodOrConstructor(ClassDesc* members, MemberDesc* method) {
   TRACE_PARSER("ParseMethodOrConstructor");
-  ASSERT(CurrentToken() == Token::kLPAREN || method->IsGetter());
+  // We are at the beginning of the formal parameters list.
+  ASSERT(CurrentToken() == Token::kLPAREN ||
+         CurrentToken() == Token::kLT ||
+         method->IsGetter());
   ASSERT(method->type != NULL);
   ASSERT(current_member_ == method);
 
   if (method->has_var) {
     ReportError(method->name_pos, "keyword var not allowed for methods");
   }
   if (method->has_final) {
     ReportError(method->name_pos, "'final' not allowed for methods");
   }
   if (method->has_abstract && method->has_static) {
     ReportError(method->name_pos,
                 "static method '%s' cannot be abstract",
                 method->name->ToCString());
      }
   if (method->has_const && !method->IsFactoryOrConstructor()) {
     ReportError(method->name_pos, "'const' not allowed for methods");
   }
   if (method->has_abstract && method->IsFactoryOrConstructor()) {
     ReportError(method->name_pos, "constructor cannot be abstract");
   }
   if (method->has_const && method->IsConstructor()) {
     current_class().set_is_const();
   }
 
+  if (CurrentToken() == Token::kLT) {
+    // Parse type parameters, but ignore them.
+    // TODO(hausner): handle type parameters.
+    if (!FLAG_generic_method_syntax) {
+      ReportError("generic type arguments not supported.");

[regis, 2016/08/24 14:14:02]

Being picky, but instead of "generic type arguments", either "generic function"
or "type parameters" would be more accurate.

+    }
+    TokenPosition type_param_pos = TokenPos();
+    if (method->IsFactoryOrConstructor()) {
+      ReportError(method->name_pos, "constructor cannot be generic");
+    }
+    if (method->IsGetter() || method->IsSetter()) {
+      ReportError(type_param_pos, "%s cannot be generic",
+          method->IsGetter() ? "getter" : "setter");
+    }
+    if (!TryParseTypeParameters()) {
+      ReportError(type_param_pos, "error in type parameters");
+    }
+  }
+
   // Parse the formal parameters.
   const bool are_implicitly_final = method->has_const;
   const bool allow_explicit_default_values = true;
   const TokenPosition formal_param_pos = TokenPos();
   method->params.Clear();
   // Static functions do not have a receiver.
   // The first parameter of a factory is the TypeArguments vector of
   // the type of the instance to be allocated.
   if (!method->has_static || method->IsConstructor()) {
     method->params.AddReceiver(ReceiverType(current_class()), formal_param_pos);
@@ skipping 580 matching lines @@
   } else if ((CurrentToken() == Token::kFACTORY) &&
       (LookaheadToken(1) != Token::kLPAREN)) {
     ConsumeToken();
     if (member.has_static) {
       ReportError("factory method cannot be explicitly marked static");
     }
     member.has_factory = true;
     member.has_static = true;
     // The result type depends on the name of the factory method.
   }
+
   // Optionally parse a type.
   if (CurrentToken() == Token::kVOID) {
     if (member.has_var || member.has_factory) {
       ReportError("void not expected");
     }
     ConsumeToken();
     ASSERT(member.type == NULL);
     member.type = &Object::void_type();
-  } else if (CurrentToken() == Token::kIDENT) {
-    // This is either a type name or the name of a method/constructor/field.
-    if ((member.type == NULL) && !member.has_factory) {
-      // We have not seen a member type yet, so we check if the next
-      // identifier could represent a type before parsing it.
-      Token::Kind follower = LookaheadToken(1);
-      // We have an identifier followed by a 'follower' token.
-      // We either parse a type or assume that no type is specified.
-      if ((follower == Token::kLT) ||  // Parameterized type.
-          (follower == Token::kGET) ||  // Getter following a type.
-          (follower == Token::kSET) ||  // Setter following a type.
-          (follower == Token::kOPERATOR) ||  // Operator following a type.
-          (Token::IsIdentifier(follower)) ||  // Member name following a type.
-          ((follower == Token::kPERIOD) &&    // Qualified class name of type,
-           (LookaheadToken(3) != Token::kLPAREN))) {  // but not a named constr.
-        ASSERT(is_top_level_);
-        // The declared type of fields is never ignored, even in unchecked mode,
-        // because getters and setters could be closurized at some time (not
-        // supported yet).
-        member.type = &AbstractType::ZoneHandle(Z,
-            ParseType(ClassFinalizer::kResolveTypeParameters));
+  } else {
+    bool found_type = false;
+    {
+      // Lookahead to determine whether the next tokens are a return type.
+      TokenPosScope saved_pos(this);
+      if (TryParseReturnType()) {
+        if (IsIdentifier() ||
+           (CurrentToken() == Token::kGET) ||
+           (CurrentToken() == Token::kSET) ||
+           (CurrentToken() == Token::kOPERATOR)) {
+          found_type = true;
+        }
       }
     }
+    if (found_type) {
+      member.type = &AbstractType::ZoneHandle(Z,
+          ParseType(ClassFinalizer::kResolveTypeParameters));
+    }
   }
 
   // Optionally parse a (possibly named) constructor name or factory.
   if (IsIdentifier() &&
       (CurrentLiteral()->Equals(members->class_name()) || member.has_factory)) {
     member.name_pos = TokenPos();
     member.name = CurrentLiteral();  // Unqualified identifier.
     ConsumeToken();
     if (member.has_factory) {
       // The factory name may be qualified, but the first identifier must match
@@ skipping 30 matching lines @@
     if (CurrentToken() == Token::kPERIOD) {
       // Named constructor.
       ConsumeToken();
       member.dict_name = ExpectIdentifier("identifier expected");
       to_concat.Add(*member.dict_name);
     }
     *member.name = Symbols::FromConcatAll(T, to_concat);
     CheckToken(Token::kLPAREN);
   } else if ((CurrentToken() == Token::kGET) && !member.has_var &&
              (LookaheadToken(1) != Token::kLPAREN) &&
+             (LookaheadToken(1) != Token::kLT) &&
              (LookaheadToken(1) != Token::kASSIGN) &&
              (LookaheadToken(1) != Token::kCOMMA)  &&
              (LookaheadToken(1) != Token::kSEMICOLON)) {
     ConsumeToken();
     member.kind = RawFunction::kGetterFunction;
     member.name_pos = this->TokenPos();
     member.name = ExpectIdentifier("identifier expected");
     // If the result type was not specified, it will be set to DynamicType.
   } else if ((CurrentToken() == Token::kSET) && !member.has_var &&
              (LookaheadToken(1) != Token::kLPAREN) &&
+             (LookaheadToken(1) != Token::kLT) &&
              (LookaheadToken(1) != Token::kASSIGN) &&
              (LookaheadToken(1) != Token::kCOMMA)  &&
              (LookaheadToken(1) != Token::kSEMICOLON))  {
     ConsumeToken();
     member.kind = RawFunction::kSetterFunction;
     member.name_pos = this->TokenPos();
     member.name = ExpectIdentifier("identifier expected");
     CheckToken(Token::kLPAREN);
     // The grammar allows a return type, so member.type is not always NULL here.
     // If no return type is specified, the return type of the setter is dynamic.
     if (member.type == NULL) {
       member.type = &Object::dynamic_type();
     }
   } else if ((CurrentToken() == Token::kOPERATOR) && !member.has_var &&
              (LookaheadToken(1) != Token::kLPAREN) &&
              (LookaheadToken(1) != Token::kASSIGN) &&
              (LookaheadToken(1) != Token::kCOMMA)  &&
              (LookaheadToken(1) != Token::kSEMICOLON)) {
+    // TODO(hausner): handle the case of a generic function named 'operator':
+    // eg: T operator<T>(a, b) => ...
     ConsumeToken();
     if (!Token::CanBeOverloaded(CurrentToken())) {
       ReportError("invalid operator overloading");
     }
     if (member.has_static) {
       ReportError("operator overloading functions cannot be static");
     }
     member.operator_token = CurrentToken();
     member.has_operator = true;
     member.kind = RawFunction::kRegularFunction;
     member.name_pos = this->TokenPos();
     member.name = &String::ZoneHandle(Z,
         Symbols::Token(member.operator_token).raw());
     ConsumeToken();
   } else if (IsIdentifier()) {
     member.name = CurrentLiteral();
     member.name_pos = TokenPos();
     ConsumeToken();
   } else {
     ReportError("identifier expected");
   }
 
   ASSERT(member.name != NULL);
-  if (CurrentToken() == Token::kLPAREN || member.IsGetter()) {
+  if (IsParameterPart() || member.IsGetter()) {
     // Constructor or method.
     if (member.type == NULL) {
       member.type = &Object::dynamic_type();
     }
     ASSERT(member.IsFactory() == member.has_factory);
     ParseMethodOrConstructor(members, &member);
   } else if (CurrentToken() ==  Token::kSEMICOLON ||
              CurrentToken() == Token::kCOMMA ||
              CurrentToken() == Token::kASSIGN) {
     // Field definition.
@@ skipping 634 matching lines @@
 
 
 // Look ahead to detect if we are seeing ident [ TypeParameters ] "(".
 // We need this lookahead to distinguish between the optional return type
 // and the alias name of a function type alias.
 // Token position remains unchanged.
 bool Parser::IsFunctionTypeAliasName() {
   if (IsIdentifier() && (LookaheadToken(1) == Token::kLPAREN)) {
     return true;
   }
-  const TokenPosition saved_pos = TokenPos();
-  bool is_alias_name = false;
+  const TokenPosScope saved_pos(this);
   if (IsIdentifier() && (LookaheadToken(1) == Token::kLT)) {
     ConsumeToken();
     if (TryParseTypeParameters() && (CurrentToken() == Token::kLPAREN)) {
-      is_alias_name = true;
+      return true;
     }
   }
-  SetPosition(saved_pos);
-  return is_alias_name;
+  return false;
 }
 
 
 // Look ahead to detect if we are seeing ident [ TypeParameters ] "=".
 // Token position remains unchanged.
 bool Parser::IsMixinAppAlias() {
   if (IsIdentifier() && (LookaheadToken(1) == Token::kASSIGN)) {
     return true;
   }
-  const TokenPosition saved_pos = TokenPos();
-  bool is_mixin_def = false;
+  const TokenPosScope saved_pos(this);
   if (IsIdentifier() && (LookaheadToken(1) == Token::kLT)) {
     ConsumeToken();
     if (TryParseTypeParameters() && (CurrentToken() == Token::kASSIGN)) {
-      is_mixin_def = true;
+      return true;
     }
   }
-  SetPosition(saved_pos);
-  return is_mixin_def;
+  return false;
 }
 
 
 void Parser::ParseTypedef(const GrowableObjectArray& pending_classes,
                           const Object& tl_owner,
                           TokenPosition metadata_pos) {
   TRACE_PARSER("ParseTypedef");
   TokenPosition declaration_pos =
       metadata_pos.IsReal() ? metadata_pos : TokenPos();
   ExpectToken(Token::kTYPEDEF);
@@ skipping 86 matching lines @@
   ASSERT(!function_type_alias.is_finalized());
   pending_classes.Add(function_type_alias, Heap::kOld);
   if (FLAG_enable_mirrors && metadata_pos.IsReal()) {
     library_.AddClassMetadata(function_type_alias,
                               tl_owner,
                               metadata_pos);
   }
 }
 
 
-// Consumes exactly one right angle bracket. If the current token is a single
-// bracket token, it is consumed normally. However, if it is a double or triple
-// bracket, it is replaced by a single or double bracket token without
+// Consumes exactly one right angle bracket. If the current token is
+// a single bracket token, it is consumed normally. However, if it is
+// a double bracket, it is replaced by a single bracket token without
 // incrementing the token index.
 void Parser::ConsumeRightAngleBracket() {
   if (token_kind_ == Token::kGT) {
     ConsumeToken();
   } else if (token_kind_ == Token::kSHR) {
     token_kind_ = Token::kGT;
   } else {
     UNREACHABLE();
   }
 }
 
 
 bool Parser::IsPatchAnnotation(TokenPosition pos) {
   if (pos == TokenPosition::kNoSource) {
     return false;
   }
-  TokenPosition saved_pos = TokenPos();
+  TokenPosScope saved_pos(this);
   SetPosition(pos);
   ExpectToken(Token::kAT);
-  bool is_patch = IsSymbol(Symbols::Patch());
-  SetPosition(saved_pos);
-  return is_patch;
+  return IsSymbol(Symbols::Patch());
 }
 
 
 TokenPosition Parser::SkipMetadata() {
   if (CurrentToken() != Token::kAT) {
     return TokenPosition::kNoSource;
   }
   TokenPosition metadata_pos = TokenPos();
   while (CurrentToken() == Token::kAT) {
     ConsumeToken();
@@ skipping 337 matching lines @@
     metadata_pos = TokenPosition::kNoSource;
   } else if (CurrentToken() == Token::kEXTERNAL) {
     ConsumeToken();
     is_external = true;
   }
   if (CurrentToken() == Token::kVOID) {
     ConsumeToken();
     result_type = Type::VoidType();
   } else {
     // Parse optional type.
-    if ((CurrentToken() == Token::kIDENT) &&
-        (LookaheadToken(1) != Token::kLPAREN)) {
+    if (IsFunctionReturnType()) {
       result_type = ParseType(ClassFinalizer::kResolveTypeParameters);
     }
   }
   const TokenPosition name_pos = TokenPos();
   const String& func_name = *ExpectIdentifier("function name expected");
 
   bool found = library_.LookupLocalObject(func_name) != Object::null();
   if (found && !is_patch) {
     ReportError(name_pos, "'%s' is already defined", func_name.ToCString());
   } else if (!found && is_patch) {
     ReportError(name_pos, "missing '%s' cannot be patched",
                 func_name.ToCString());
   }
   String& accessor_name = String::Handle(Z, Field::GetterName(func_name));
   if (library_.LookupLocalObject(accessor_name) != Object::null()) {
     ReportError(name_pos, "'%s' is already defined as getter",
                 func_name.ToCString());
   }
   // A setter named x= may co-exist with a function named x, thus we do
   // not need to check setters.
 
+  if (CurrentToken() == Token::kLT) {
+    // Type parameters of generic function.
+    // TODO(hausner): handle type parameters.
+    if (!FLAG_generic_method_syntax) {
+      ReportError("generic functions not supported");
+    }
+    TokenPosition type_arg_pos = TokenPos();
+    if (!TryParseTypeParameters()) {
+      ReportError(type_arg_pos, "error in type parameters");
+    }
+  }
+
   CheckToken(Token::kLPAREN);
   const TokenPosition function_pos = TokenPos();
   ParamList params;
   const bool allow_explicit_default_values = true;
   ParseFormalParameterList(allow_explicit_default_values, false, &params);
 
   const TokenPosition modifier_pos = TokenPos();
   RawFunction::AsyncModifier func_modifier = ParseFunctionModifier();
 
   TokenPosition function_end_pos = function_pos;
@@ skipping 2072 matching lines @@
   TRACE_PARSER("ParseFunctionStatement");
   AbstractType& result_type = AbstractType::Handle(Z);
   const String* variable_name = NULL;
   const String* function_name = NULL;
 
   result_type = Type::DynamicType();
 
   const TokenPosition function_pos = TokenPos();
   TokenPosition metadata_pos = TokenPosition::kNoSource;
   if (is_literal) {
-    ASSERT(CurrentToken() == Token::kLPAREN);
+    ASSERT(CurrentToken() == Token::kLPAREN || CurrentToken() == Token::kLT);
     function_name = &Symbols::AnonymousClosure();
   } else {
     metadata_pos = SkipMetadata();
     if (CurrentToken() == Token::kVOID) {
       ConsumeToken();
       result_type = Type::VoidType();
-    } else if ((CurrentToken() == Token::kIDENT) &&
-               (LookaheadToken(1) != Token::kLPAREN)) {
+    } else if (IsFunctionReturnType()) {
       result_type = ParseType(ClassFinalizer::kCanonicalize);
     }
     const TokenPosition name_pos = TokenPos();
     variable_name = ExpectIdentifier("function name expected");
     function_name = variable_name;
 
     // Check that the function name has not been referenced
     // before this declaration.
     ASSERT(current_block_ != NULL);
     const TokenPosition previous_pos =
         current_block_->scope->PreviousReferencePos(*function_name);
     if (previous_pos.IsReal()) {
       ASSERT(!script_.IsNull());
       intptr_t line_number;
       script_.GetTokenLocation(previous_pos, &line_number, NULL);
       ReportError(name_pos,
                   "identifier '%s' previously used in line %" Pd "",
                   function_name->ToCString(),
                   line_number);
     }
   }
+
+  if (CurrentToken() == Token::kLT) {
+    if (!FLAG_generic_method_syntax) {
+      ReportError("generic functions not supported");
+    }
+    TokenPosition type_arg_pos = TokenPos();
+    // TODO(hausner): handle type parameters of generic function.
+    if (!TryParseTypeParameters()) {
+      ReportError(type_arg_pos, "error in type parameters");
+    }
+  }
+
   CheckToken(Token::kLPAREN);
 
   // Check whether we have parsed this closure function before, in a previous
   // compilation. If so, reuse the function object, else create a new one
   // and register it in the current class.
   // Note that we cannot share the same closure function between the closurized
   // and non-closurized versions of the same parent function.
   Function& function = Function::ZoneHandle(Z);
   bool found_func = true;
   // TODO(hausner): There could be two different closures at the given
@@ skipping 153 matching lines @@
     AstNode* initialization = new(Z) StoreLocalNode(
         function_pos, function_variable, closure);
     return initialization;
   }
 }
 
 
 // Returns true if the current and next tokens can be parsed as type
 // parameters. Current token position is not saved and restored.
 bool Parser::TryParseTypeParameters() {
-  if (CurrentToken() == Token::kLT) {
-    // We are possibly looking at type parameters. Find closing ">".
-    int nesting_level = 0;
-    do {
-      if (CurrentToken() == Token::kLT) {
-        nesting_level++;
-      } else if (CurrentToken() == Token::kGT) {
-        nesting_level--;
-      } else if (CurrentToken() == Token::kSHR) {
-        nesting_level -= 2;
-      } else if (CurrentToken() == Token::kIDENT) {
-        // Check to see if it is a qualified identifier.
-        if (LookaheadToken(1) == Token::kPERIOD) {
-          // Consume the identifier, the period will be consumed below.
-          ConsumeToken();
-        }
-      } else if (CurrentToken() != Token::kCOMMA &&
-                 CurrentToken() != Token::kEXTENDS) {
-        // We are looking at something other than type parameters.
-        return false;
+  ASSERT(CurrentToken() == Token::kLT);
+  int nesting_level = 0;
+  do {
+    Token::Kind ct = CurrentToken();
+    if (ct == Token::kLT) {
+      nesting_level++;
+    } else if (ct == Token::kGT) {
+      nesting_level--;
+    } else if (ct == Token::kSHR) {
+      nesting_level -= 2;
+    } else if (ct == Token::kIDENT) {
+      // Check to see if it is a qualified identifier.
+      if (LookaheadToken(1) == Token::kPERIOD) {
+        // Consume the identifier, the period will be consumed below.
+        ConsumeToken();
       }
-      ConsumeToken();
-    } while (nesting_level > 0);
-    if (nesting_level < 0) {
+    } else if ((ct != Token::kCOMMA) &&
+               (ct != Token::kEXTENDS) &&
+               (!FLAG_generic_method_syntax || (ct != Token::kSUPER))) {
+      // We are looking at something other than type parameters.
       return false;
     }
+    ConsumeToken();
+  } while (nesting_level > 0);
+  if (nesting_level < 0) {
+    return false;
   }
   return true;
 }
 
 
+// Returns true if the next tokens can be parsed as type parameters.
+bool Parser::IsTypeParameters() {
+  if (CurrentToken() == Token::kLT) {
+    TokenPosScope param_pos(this);
+    if (!TryParseTypeParameters()) {
+      return false;
+    }
+    return true;
+  }
+  return false;
+}
+
+
+// Returns true if the next tokens are [ typeParameters ] '('.
+bool Parser::IsParameterPart() {
+  if (CurrentToken() == Token::kLPAREN) {
+    return true;
+  }
+  if (CurrentToken() == Token::kLT) {
+    TokenPosScope type_arg_pos(this);
+    if (!TryParseTypeParameters()) {
+      return false;
+    }
+    return CurrentToken() == Token::kLPAREN;
+  }
+  return false;
+}
+
+
+// Returns true if the current and next tokens can be parsed as type
+// arguments. Current token position is not saved and restored.
+bool Parser::TryParseTypeArguments() {
+  ASSERT(CurrentToken() == Token::kLT);
+  int nesting_level = 0;
+  do {
+    Token::Kind ct = CurrentToken();
+    if (ct == Token::kLT) {
+      nesting_level++;
+    } else if (ct == Token::kGT) {
+      nesting_level--;
+    } else if (ct == Token::kSHR) {
+      nesting_level -= 2;
+    } else if (ct == Token::kIDENT) {
+      // Check to see if it is a qualified identifier.
+      if (LookaheadToken(1) == Token::kPERIOD) {
+        // Consume the identifier, the period will be consumed below.
+        ConsumeToken();
+      }
+    } else if (ct != Token::kCOMMA) {
+      return false;
+    }
+    ConsumeToken();
+  } while (nesting_level > 0);
+  if (nesting_level < 0) {
+    return false;
+  }
+  return true;
+}
+
+
+// Returns true if the next tokens are [ typeArguments ] '('.
+bool Parser::IsArgumentPart() {
+  if (CurrentToken() == Token::kLPAREN) {
+    return true;
+  }
+  if (CurrentToken() == Token::kLT) {
+    TokenPosScope type_arg_pos(this);
+    if (!TryParseTypeArguments()) {
+      return false;
+    }
+    return CurrentToken() == Token::kLPAREN;
+  }
+  return false;
+}
+
+
 bool Parser::IsSimpleLiteral(const AbstractType& type, Instance* value) {
   // Assigning null never causes a type error.
   if (CurrentToken() == Token::kNULL) {
     *value = Instance::null();
     return true;
   }
   // If the type of the const field is guaranteed to be instantiated once
   // resolved at class finalization time, and if the type of the literal is one
   // of int, double, String, or bool, then preset the field with the value and
   // perform the type check (in checked mode only) at finalization time.
@@ skipping 143 matching lines @@
           (CurrentToken() == Token::kASSIGN)) {
         is_var_decl = true;
       }
     }
   }
   SetPosition(saved_pos);
   return is_var_decl;
 }
 
 
+// Look ahead to see if the following tokens are a return type followed
+// by an identifier.
+bool Parser::IsFunctionReturnType() {
+  TokenPosScope decl_pos(this);
+  if (TryParseReturnType()) {
+    if (IsIdentifier()) {
+      // Return type followed by function name.
+      return true;
+    }
+  }
+  return false;
+}
+
+
 // Look ahead to detect whether the next tokens should be parsed as
 // a function declaration. Token position remains unchanged.
 bool Parser::IsFunctionDeclaration() {
-  const TokenPosition saved_pos = TokenPos();
   bool is_external = false;
+  TokenPosScope decl_pos(this);
   SkipMetadata();
-  if (is_top_level_ && (CurrentToken() == Token::kEXTERNAL)) {
+  if ((is_top_level_) && (CurrentToken() == Token::kEXTERNAL)) {
     // Skip over 'external' for top-level function declarations.
     is_external = true;
     ConsumeToken();
   }
-  if (IsIdentifier() && (LookaheadToken(1) == Token::kLPAREN)) {
-    // Possibly a function without explicit return type.
-    ConsumeToken();  // Consume function identifier.
-  } else if (TryParseReturnType()) {
+  const TokenPosition type_or_name_pos = TokenPos();
+  if (TryParseReturnType()) {
     if (!IsIdentifier()) {
-      SetPosition(saved_pos);
-      return false;
+      SetPosition(type_or_name_pos);
     }
-    ConsumeToken();  // Consume function identifier.
   } else {
-    SetPosition(saved_pos);
+    SetPosition(type_or_name_pos);
+  }
+  // Check for function name followed by optional type parameters.
+  if (!IsIdentifier()) {
     return false;
   }
+  ConsumeToken();
+  if ((CurrentToken() == Token::kLT) && !TryParseTypeParameters()) {
+    return false;
+  }
+
+  // Optional type, function name and optinal type parameters are parsed.
+  if (CurrentToken() != Token::kLPAREN) {
+    return false;
+  }
+
   // Check parameter list and the following token.
-  if (CurrentToken() == Token::kLPAREN) {
-    SkipToMatchingParenthesis();
-    if ((CurrentToken() == Token::kLBRACE) ||
-        (CurrentToken() == Token::kARROW) ||
-        (is_top_level_ && IsSymbol(Symbols::Native())) ||
-        is_external ||
-        IsSymbol(Symbols::Async()) ||
-        IsSymbol(Symbols::Sync())) {
-      SetPosition(saved_pos);
-      return true;
-    }
+  SkipToMatchingParenthesis();
+  if ((CurrentToken() == Token::kLBRACE) ||
+      (CurrentToken() == Token::kARROW) ||
+      (is_top_level_ && IsSymbol(Symbols::Native())) ||
+      is_external ||
+      IsSymbol(Symbols::Async()) ||
+      IsSymbol(Symbols::Sync())) {
+    return true;
   }
-  SetPosition(saved_pos);
   return false;
 }
 
 
 bool Parser::IsTopLevelAccessor() {
-  const TokenPosition saved_pos = TokenPos();
+  const TokenPosScope saved_pos(this);
   if (CurrentToken() == Token::kEXTERNAL) {
     ConsumeToken();
   }
   if ((CurrentToken() == Token::kGET) || (CurrentToken() == Token::kSET)) {
-    SetPosition(saved_pos);
     return true;
   }
   if (TryParseReturnType()) {
     if ((CurrentToken() == Token::kGET) || (CurrentToken() == Token::kSET)) {
       if (Token::IsIdentifier(LookaheadToken(1))) {  // Accessor name.
-        SetPosition(saved_pos);
         return true;
       }
     }
   }
-  SetPosition(saved_pos);
   return false;
 }
 
 
 bool Parser::IsFunctionLiteral() {
-  if (CurrentToken() != Token::kLPAREN || !allow_function_literals_) {
+  if (!allow_function_literals_) {
     return false;
   }
-  const TokenPosition saved_pos = TokenPos();
-  bool is_function_literal = false;
-  SkipToMatchingParenthesis();
-  ParseFunctionModifier();
-  if ((CurrentToken() == Token::kLBRACE) ||
-      (CurrentToken() == Token::kARROW)) {
-    is_function_literal = true;
+  if ((CurrentToken() == Token::kLPAREN) || (CurrentToken() == Token::kLT)) {
+    TokenPosScope saved_pos(this);
+    if ((CurrentToken() == Token::kLT) && !TryParseTypeParameters()) {
+      return false;
+    }
+    if (CurrentToken() != Token::kLPAREN) {
+      return false;
+    }
+    SkipToMatchingParenthesis();
+    ParseFunctionModifier();
+    if ((CurrentToken() == Token::kLBRACE) ||
+        (CurrentToken() == Token::kARROW)) {
+       return true;
+    }
   }
-  SetPosition(saved_pos);
-  return is_function_literal;
+  return false;
 }
 
 
 // Current token position is the token after the opening ( of the for
 // statement. Returns true if we recognize a for ( .. in expr)
 // statement.
 bool Parser::IsForInStatement() {
-  const TokenPosition saved_pos = TokenPos();
-  bool result = false;
+  const TokenPosScope saved_pos(this);
   // Allow const modifier as well when recognizing a for-in statement
   // pattern. We will get an error later if the loop variable is
   // declared with const.
   if (CurrentToken() == Token::kVAR ||
       CurrentToken() == Token::kFINAL ||
       CurrentToken() == Token::kCONST) {
     ConsumeToken();
   }
   if (IsIdentifier()) {
     if (LookaheadToken(1) == Token::kIN) {
-      result = true;
+      return true;
     } else if (TryParseOptionalType()) {
       if (IsIdentifier()) {
         ConsumeToken();
       }
-      result = (CurrentToken() == Token::kIN);
+      return CurrentToken() == Token::kIN;
     }
   }
-  SetPosition(saved_pos);
-  return result;
+  return false;
 }
 
 
 static bool ContainsAbruptCompletingStatement(SequenceNode* seq);
 
 static bool IsAbruptCompleting(AstNode* statement) {
   return statement->IsReturnNode() ||
          statement->IsJumpNode()   ||
          statement->IsThrowNode()  ||
          (statement->IsSequenceNode() &&
@@ skipping 3379 matching lines @@
           left = new(Z) TypeNode(primary->token_pos(), type_parameter);
         } else {
           // Super field access handled in ParseSuperFieldAccess(),
           // super calls handled in ParseSuperCall().
           ASSERT(!primary_node->IsSuper());
           left = LoadFieldIfUnresolved(left);
         }
       }
       const TokenPosition ident_pos = TokenPos();
       String* ident = ExpectIdentifier("identifier expected");
-      if (CurrentToken() == Token::kLPAREN) {
-        // Identifier followed by a opening paren: method call.
+      if (IsArgumentPart()) {
+        // Identifier followed by optional type arguments and opening paren:
+        // method call.
+        if (CurrentToken() == Token::kLT) {
+          // Type arguments.
+          if (!FLAG_generic_method_syntax) {
+            ReportError("generic type arguments not supported.");

[regis, 2016/08/24 14:14:02]

I would drop "generic".
Or maybe "type arguments of generic function not supported".
Or simply "generic function not supported".

+          }
+          // TODO(hausner): handle type arguments.
+          ParseTypeArguments(ClassFinalizer::kIgnore);
+        }
         if (left->IsPrimaryNode() &&
             left->AsPrimaryNode()->primary().IsClass()) {
           // Static method call prefixed with class name.
           const Class& cls = Class::Cast(left->AsPrimaryNode()->primary());
           selector = ParseStaticCall(cls, *ident, ident_pos);
         } else {
           selector = ParseInstanceCall(left, *ident, ident_pos, is_conditional);
         }
       } else {
         // Field access.
@@ skipping 71 matching lines @@
               TypeParameter::Cast(primary_node->primary()),
               ClassFinalizer::kCanonicalize);
           ASSERT(!type_parameter.IsMalformed());
           array = new(Z) TypeNode(primary_pos, type_parameter);
         } else {
           UNREACHABLE();  // Internal parser error.
         }
       }
       selector =  new(Z) LoadIndexedNode(
           bracket_pos, array, index, Class::ZoneHandle(Z));
-    } else if (CurrentToken() == Token::kLPAREN) {
+    } else if (IsArgumentPart()) {
+      if (CurrentToken() == Token::kLT) {
+        // Type arguments.
+        if (!FLAG_generic_method_syntax) {
+          ReportError("generic type arguments not supported.");

[regis, 2016/08/24 14:14:02]

ditto

+        }
+        // TODO(hausner): handle type arguments.
+        ParseTypeArguments(ClassFinalizer::kIgnore);
+      }
       if (left->IsPrimaryNode()) {
         PrimaryNode* primary_node = left->AsPrimaryNode();
         const TokenPosition primary_pos = primary_node->token_pos();
         if (primary_node->primary().IsFunction()) {
           const Function& func = Function::Cast(primary_node->primary());
           const String& func_name = String::ZoneHandle(Z, func.name());
           if (func.is_static()) {
             // Parse static function call.
             Class& cls = Class::Handle(Z, func.Owner());
             selector = ParseStaticCall(cls, func_name, primary_pos);
@@ skipping 2600 matching lines @@
       ConsumeToken();
     } else {
       break;
     }
   }
   ExpectToken(Token::kRBRACE);
 }
 
 
 void Parser::SkipActualParameters() {
+  if (CurrentToken() == Token::kLT) {
+    SkipTypeArguments();
+  }
   ExpectToken(Token::kLPAREN);
   while (CurrentToken() != Token::kRPAREN) {
     if (IsIdentifier() && (LookaheadToken(1) == Token::kCOLON)) {
       // Named actual parameter.
       ConsumeToken();
       ConsumeToken();
     }
     SkipNestedExpr();
     if (CurrentToken() == Token::kCOMMA) {
       ConsumeToken();
@@ skipping 147 matching lines @@
         ExpectIdentifier("identifier or [ expected after ..");
       }
     } else if ((current_token == Token::kPERIOD) ||
         (current_token == Token::kQM_PERIOD)) {
       ConsumeToken();
       ExpectIdentifier("identifier expected");
     } else if (current_token == Token::kLBRACK) {
       ConsumeToken();
       SkipNestedExpr();
       ExpectToken(Token::kRBRACK);
-    } else if (current_token == Token::kLPAREN) {
+    } else if (IsArgumentPart()) {
       SkipActualParameters();
     } else {
       break;
     }
   }
 }
 
 void Parser::SkipPostfixExpr() {
   SkipPrimary();
   if (CurrentToken() == Token::kHASH) {
@@ skipping 183 matching lines @@
     const ArgumentListNode& function_args,
     const LocalVariable* temp_for_last_arg,
     bool is_super_invocation) {
   UNREACHABLE();
   return NULL;
 }
 
 }  // namespace dart
 
 #endif  // DART_PRECOMPILED_RUNTIME