Add primitive to create closures and use it for closure conversion

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

 library;
 import self as self;
 import "dart:core" as core;
 
 class C<T extends core::Object> extends core::Object {
-  field dynamic v = new self::Closure#C#v#function::•<self::C::T>(null);
-  final field dynamic y = new self::Closure#C#y#function::•(null);
-  static final field dynamic z = new self::Closure#C#z#function::•(null);
+  field dynamic v = MakeClosure<(dynamic) → dynamic>(self::closure#C#v#function, null);
+  final field dynamic y = MakeClosure<() → dynamic>(self::closure#C#y#function, null);
+  static final field dynamic z = MakeClosure<() → dynamic>(self::closure#C#z#function, null);
   constructor •() → void
     : super core::Object::•()
     ;
 }
-class Closure#C#v#function<T extends core::Object> extends core::Object implements core::Function {
-  field core::String note = "This is temporary. The VM doesn't need closure classes.";
-  field Vector context;
-  constructor •(final Vector context) → dynamic
-    : self::Closure#C#v#function::context = context
-    ;
-  method call(dynamic x) → dynamic {
-    "This is a temporary solution. In the VM, this will become an additional parameter.";
-    final Vector #contextParameter = this.{self::Closure#C#v#function::context};
-    return x is self::Closure#C#v#function::T;
-  }
-}
-class Closure#C#y#function extends core::Object implements core::Function {
-  field core::String note = "This is temporary. The VM doesn't need closure classes.";
-  field Vector context;
-  constructor •(final Vector context) → dynamic
-    : self::Closure#C#y#function::context = context
-    ;
-  method call() → dynamic {
-    "This is a temporary solution. In the VM, this will become an additional parameter.";
-    final Vector #contextParameter = this.{self::Closure#C#y#function::context};
-    return "y";
-  }
-}
-class Closure#C#z#function extends core::Object implements core::Function {
-  field core::String note = "This is temporary. The VM doesn't need closure classes.";
-  field Vector context;
-  constructor •(final Vector context) → dynamic
-    : self::Closure#C#z#function::context = context
-    ;
-  method call() → dynamic {
-    "This is a temporary solution. In the VM, this will become an additional parameter.";
-    final Vector #contextParameter = this.{self::Closure#C#z#function::context};
-    return "z";
-  }
-}
-class Closure#x#function extends core::Object implements core::Function {
-  field core::String note = "This is temporary. The VM doesn't need closure classes.";
-  field Vector context;
-  constructor •(final Vector context) → dynamic
-    : self::Closure#x#function::context = context
-    ;
-  method call() → dynamic {
-    "This is a temporary solution. In the VM, this will become an additional parameter.";
-    final Vector #contextParameter = this.{self::Closure#x#function::context};
-    return "x";
-  }
-}
-static field dynamic x = new self::Closure#x#function::•(null);
+static field dynamic x = MakeClosure<() → dynamic>(self::closure#x#function, null);
 static method main() → dynamic {
   if(!new self::C::•<core::String>().v(""))
     throw "C<String>.v false on String";
   if(new self::C::•<core::String>().v(0))
     throw "C<String>.v true on int";
   if(new self::C::•<core::String>().v(null))
     throw "C<String>.v true on null";
   if(new self::C::•<core::int>().v(""))
     throw "C<int>.v true on String";
   if(!new self::C::•<core::int>().v(0))
     throw "C<int>.v false on int";
   if(new self::C::•<core::int>().v(null))
     throw "C<int>.v true on null";
   if(!"x".==(self::x.call()))
     throw "x";
   if(!"y".==(new self::C::•<core::String>().y()))
     throw "y";
   if(!"z".==(self::C::z.call()))
     throw "z";
 }
+static method closure#C#v#function(Vector #contextParameter, dynamic x) → dynamic {
+  return x is dynamic;
+}
+static method closure#C#y#function(Vector #contextParameter) → dynamic {
+  return "y";
+}
+static method closure#C#z#function(Vector #contextParameter) → dynamic {
+  return "z";
+}
+static method closure#x#function(Vector #contextParameter) → dynamic {
+  return "x";
+}