Add primitive to create closures and use it for closure conversion

pkg/kernel/lib/type_checker.dart

Index: pkg/kernel/lib/type_checker.dart
diff --git a/pkg/kernel/lib/type_checker.dart b/pkg/kernel/lib/type_checker.dart
index bee75b2f1aeb20aa66c345e0a106dd51b54c4073..6c48a6d91d17175c928b6e0c574200e659ab3fb9 100644
--- a/pkg/kernel/lib/type_checker.dart
+++ b/pkg/kernel/lib/type_checker.dart
@@ -690,6 +690,11 @@ class TypeCheckingVisitor
   }
 
   @override
+  DartType visitVectorCreation(VectorCreation node) {
+    return const VectorType();
+  }
+
+  @override
   DartType visitVectorGet(VectorGet node) {
     var type = visitExpression(node.vectorExpression);
     if (type is! VectorType) {
@@ -726,8 +731,15 @@ class TypeCheckingVisitor
   }
 
   @override
-  DartType visitVectorCreation(VectorCreation node) {
-    return const VectorType();
+  visitClosureCreation(ClosureCreation node) {
+    var contextType = visitExpression(node.contextVector);
+    if (contextType is! VectorType) {
+      fail(
+          node.contextVector,
+          "The second child of 'ClosureConversion' node is supposed to be a "
+          "Vector, but $contextType found.");
+    }
+    return node.functionType;
   }
 
   @override