Add --modules=node support

test/codegen/expect/collection/src/canonicalized_map.js

Index: test/codegen/expect/collection/src/canonicalized_map.js
diff --git a/test/codegen/expect/collection/src/canonicalized_map.js b/test/codegen/expect/collection/src/canonicalized_map.js
index ad42dd3c4b32dc65fe68fe881070a1f7314692dc..7b8fece4d53b296e2df41c2faae7aa38a1f8682a 100644
--- a/test/codegen/expect/collection/src/canonicalized_map.js
+++ b/test/codegen/expect/collection/src/canonicalized_map.js
@@ -62,7 +62,7 @@ dart_library.library('collection/src/canonicalized_map', null, /* Imports */[
         return this[_base].isNotEmpty;
       }
       get keys() {
-        return this[_base].values[dartx.map](dart.fn(pair => pair.first, K, [utils.Pair$(K, V)]));
+        return dart.as(this[_base].values[dartx.map](dart.fn(pair => pair.first, K, [utils.Pair$(K, V)])), core.Iterable$(K));
       }
       get length() {
         return this[_base].length;
@@ -78,7 +78,7 @@ dart_library.library('collection/src/canonicalized_map', null, /* Imports */[
         return pair == null ? null : pair.last;
       }
       get values() {
-        return this[_base].values[dartx.map](dart.fn(pair => pair.last, V, [utils.Pair$(K, V)]));
+        return dart.as(this[_base].values[dartx.map](dart.fn(pair => pair.last, V, [utils.Pair$(K, V)])), core.Iterable$(V));
       }
       toString() {
         return collection.Maps.mapToString(this);
@@ -109,7 +109,7 @@ dart_library.library('collection/src/canonicalized_map', null, /* Imports */[
     });
     return CanonicalizedMap;
   });
-  let CanonicalizedMap = CanonicalizedMap$();
+  const CanonicalizedMap = CanonicalizedMap$();
   // Exports:
   exports.CanonicalizedMap$ = CanonicalizedMap$;
   exports.CanonicalizedMap = CanonicalizedMap;