Preserve type variables in closure conversion.

pkg/kernel/testcases/closures/type_variables.dart.expect

-library;
-import self as self;
-import "dart:core" as core;
-
-class C<T extends core::Object, S extends core::Object> extends core::Object {
-  constructor internal() → void
-    : super core::Object::•()
-    ;
-  method foo(self::C::S s) → dynamic {
-    final Vector #context = MakeVector(2);
-    #context[1] = this;
-    return MakeClosure<(dynamic) → dynamic>(self::closure#C#foo#function, #context);
-  }
-  method bar() → dynamic {
-    self::C<self::C::T, self::C::S> self = this;
-  }
-  method baz() → dynamic {
-    return MakeClosure<() → dynamic>(self::closure#C#baz#function, null);
-  }
-  static factory •<T extends core::Object, S extends core::Object>() → self::C<self::C::•::T, self::C::•::S> {
-    final () → dynamic local = MakeClosure<() → dynamic>(self::closure#C#function#local, null);
-    return local.call();
-  }
-}
-static method main(dynamic arguments) → dynamic {
-  core::print(self::C::•<core::String, core::String>().foo(null).call(arguments.first));
-  dynamic c = self::C::•<core::int, core::int>().baz().call().call();
-  if(!(c is self::C<core::int, core::int>))
-    throw "${c} fails type test 'is C<int, int>'";
-  if(c is self::C<core::String, core::String>) {
-    throw "${c{self::C<core::String, core::String>}} passes type test 'is C<String, String>'";
-  }
-  core::print(c);
-}
-static method closure#C#foo#function(Vector #contextParameter, dynamic x) → dynamic {
-  dynamic y = x;
-  core::Object z = y;
-  self::C<dynamic, dynamic> self = #contextParameter[1];
-  return z as dynamic;
-}
-static method closure#C#baz#function#function(Vector #contextParameter) → dynamic {
-  return self::C::•<dynamic, dynamic>();
-}
-static method closure#C#baz#function(Vector #contextParameter) → dynamic {
-  return MakeClosure<() → dynamic>(self::closure#C#baz#function#function, #contextParameter);
-}
-static method closure#C#function#local(Vector #contextParameter) → dynamic {
-  self::C<dynamic, dynamic> self = new self::C::internal<dynamic, dynamic>();
-  return self;
-}