diff --git a/package.json b/package.json
index b032c756b8..a154cc13d8 100644
--- a/package.json
+++ b/package.json
@@ -112,7 +112,8 @@
     "publish-coverage-and-typedocs": "yarn typedoc && yarn coverage && yarn build:pages && yarn deploy:pages",
     "jj": "npx ts-node src/json-cli/jj.ts",
     "upgrade:check": "npx npm-check-updates@16.14",
-    "upgrade:interactive": "npx npm-check-updates@16.14 --interactive"
+    "upgrade:interactive": "npx npm-check-updates@16.14 --interactive",
+    "test:types": "npx tsc --noEmit"
   },
   "peerDependencies": {
     "rxjs": "7",
diff --git a/src/json-crdt-extensions/cnt/__demos__/docs.ts b/src/json-crdt-extensions/cnt/__demos__/docs.ts
index aff2ecb0cd..16db90b7ec 100644
--- a/src/json-crdt-extensions/cnt/__demos__/docs.ts
+++ b/src/json-crdt-extensions/cnt/__demos__/docs.ts
@@ -7,16 +7,16 @@
  */
 
 import {Model, s} from '../../../json-crdt';
-import {CntExt} from '..';
+import {cnt} from '..';
 
 console.clear();
 
 const model = Model.withLogicalClock(1234);
 
-model.ext.register(CntExt);
+model.ext.register(cnt);
 
 model.api.root({
-  counter: CntExt.new(1),
+  counter: cnt.new(1),
 });
 console.log(model + '');
 
@@ -24,7 +24,7 @@ console.log(model + '');
 // 2-3 days for finding damages ...
 // ..
 
-const api = model.api.in(['counter']).asExt(CntExt);
+const api = model.api.in(['counter']).asExt(cnt);
 const values = api.view();
 
 console.log(values);
diff --git a/src/json-crdt-extensions/cnt/__demos__/usage.ts b/src/json-crdt-extensions/cnt/__demos__/usage.ts
index 8a172e9a91..f27075db14 100644
--- a/src/json-crdt-extensions/cnt/__demos__/usage.ts
+++ b/src/json-crdt-extensions/cnt/__demos__/usage.ts
@@ -7,23 +7,23 @@
  */
 
 import {Model, s} from '../../../json-crdt';
-import {CntExt} from '..';
+import {cnt} from '..';
 
 console.clear();
 
 const model = Model.withLogicalClock(1234);
 
-model.ext.register(CntExt);
+model.ext.register(cnt);
 
 model.api.root({
-  cnt: CntExt.new(42),
+  cnt: cnt.new(42),
 });
 
 console.log('');
 console.log('Initial value:');
 console.log(model + '');
 
-const api = model.api.in(['cnt']).asExt(CntExt);
+const api = model.api.in(['cnt']).asExt(cnt);
 
 api.inc(10);
 
diff --git a/src/json-crdt-extensions/mval/__demos__/docs.ts b/src/json-crdt-extensions/mval/__demos__/docs.ts
index 95d3d86463..c8fbdd1da9 100644
--- a/src/json-crdt-extensions/mval/__demos__/docs.ts
+++ b/src/json-crdt-extensions/mval/__demos__/docs.ts
@@ -7,20 +7,20 @@
  */
 
 import {Model, s} from '../../../json-crdt';
-import {MvalExt} from '..';
+import {mval} from '..';
 
 console.clear();
 
 const model = Model.withLogicalClock(1234);
 
-model.ext.register(MvalExt);
+model.ext.register(mval);
 
 model.api.root({
-  score: MvalExt.new(1),
+  score: mval.new(1),
 });
 console.log(model + '');
 
-const api = model.api.in(['score']).asExt(MvalExt);
+const api = model.api.in(['score']).asExt(mval);
 const values = api.view();
 
 console.log(values);
diff --git a/src/json-crdt-extensions/mval/__demos__/usage.ts b/src/json-crdt-extensions/mval/__demos__/usage.ts
index 11d6b58cfc..caa6b4fb3b 100644
--- a/src/json-crdt-extensions/mval/__demos__/usage.ts
+++ b/src/json-crdt-extensions/mval/__demos__/usage.ts
@@ -7,18 +7,18 @@
  */
 
 import {Model, s} from '../../../json-crdt';
-import {MvalExt} from '..';
+import {mval} from '..';
 
 console.clear();
 
 const model = Model.withLogicalClock(1234);
 
-model.ext.register(MvalExt);
+model.ext.register(mval);
 
 model.api.root({
   obj: {
     name: s.con('John'),
-    score: MvalExt.new(s.con(1)),
+    score: mval.new(s.con(1)),
   },
 });
 
@@ -26,7 +26,7 @@ console.log('');
 console.log('Initial value:');
 console.log(model + '');
 
-const api = model.api.in(['obj', 'score']).asExt(MvalExt);
+const api = model.api.in(['obj', 'score']).asExt(mval);
 
 api.set(s.con(5));
 
@@ -36,7 +36,7 @@ console.log(model + '');
 
 const model2 = model.fork();
 
-const api2 = model2.api.in(['obj', 'score']).asExt(MvalExt);
+const api2 = model2.api.in(['obj', 'score']).asExt(mval);
 
 api.set(s.con(10));
 api2.set(s.con(20));
diff --git a/src/json-crdt-extensions/mval/__demos__/view.ts b/src/json-crdt-extensions/mval/__demos__/view.ts
index bd2f26f497..17e020d80d 100644
--- a/src/json-crdt-extensions/mval/__demos__/view.ts
+++ b/src/json-crdt-extensions/mval/__demos__/view.ts
@@ -7,15 +7,15 @@
  */
 
 import {Model, s} from '../../../json-crdt';
-import {MvalExt} from '..';
+import {mval} from '..';
 
 console.clear();
 
 const model = Model.withLogicalClock(1234);
 
-model.ext.register(MvalExt);
+model.ext.register(mval);
 
-model.api.root(MvalExt.new(s.con(1)));
+model.api.root(mval.new(s.con(1)));
 
 console.log('');
 console.log('Model with extension:');
diff --git a/src/json-crdt/__demos__/events-level2-arr.ts b/src/json-crdt/__demos__/events-level2-arr.ts
index 755a9753f1..0af7c8d16f 100644
--- a/src/json-crdt/__demos__/events-level2-arr.ts
+++ b/src/json-crdt/__demos__/events-level2-arr.ts
@@ -66,10 +66,9 @@ const main = async () => {
   console.log('More changes which result in only model change:');
   console.log('');
   // model.api.transaction(() => {
-  model.api
-    .arr(['my', 'deep', 'arr'])
-    .del(1, 1)
-    .ins(1, [konst(2)]);
+  const arrNode = model.api.arr(['my', 'deep', 'arr']);
+  arrNode.del(1, 1);
+  arrNode.ins(1, [konst(2)]);
   // });
   await new Promise((r) => setTimeout(r, 1));
   console.log('');
diff --git a/src/json-crdt/__demos__/toString-array.ts b/src/json-crdt/__demos__/toString-array.ts
index b7fc167d47..da5d7b30c9 100644
--- a/src/json-crdt/__demos__/toString-array.ts
+++ b/src/json-crdt/__demos__/toString-array.ts
@@ -25,7 +25,9 @@ model.api.root({
 
 const str = model.api.str(['foo']);
 
-str.ins(3, 'def').ins(6, 'ghi').del(1, 2);
+str.ins(3, 'def');
+str.ins(6, 'ghi');
+str.del(1, 2);
 
 model.api.obj([]).del(['baz']);
 model.api.obj([]).set({
diff --git a/src/json-crdt/__demos__/toString-object.ts b/src/json-crdt/__demos__/toString-object.ts
index 46282df055..51c7f21ef5 100644
--- a/src/json-crdt/__demos__/toString-object.ts
+++ b/src/json-crdt/__demos__/toString-object.ts
@@ -54,22 +54,24 @@ console.log('After adding a nested object:');
 console.log('');
 console.log(model.toString());
 
-model.api
-  .obj([])
-  .set({
-    about: 'I am a software engineer. I like to write code. (Codepilot wrote this demo.)',
-    verified: true,
-    sex: null,
-  })
-  .val(['age'])
-  .set(18);
+const objNode = model.api.obj([]);
+objNode.set({
+  about: 'I am a software engineer. I like to write code. (Codepilot wrote this demo.)',
+  verified: true,
+  sex: null,
+});
+objNode.val(['age']);
+objNode.set(18);
 
 console.log('');
 console.log('Editing /name field a bit more:');
 console.log('');
 console.log(model.toString());
 
-model.api.str(['name']).del(7, 3).ins(7, 'Bravo!').ins(0, '💪 ');
+const strNode = model.api.str(['name']);
+strNode.del(7, 3);
+strNode.ins(7, 'Bravo!');
+strNode.ins(0, '💪 ');
 
 console.log('');
 console.log('After some more name editing:');
diff --git a/src/json-crdt/__demos__/toString-string.ts b/src/json-crdt/__demos__/toString-string.ts
index 6be60f8215..f84e0ba2bc 100644
--- a/src/json-crdt/__demos__/toString-string.ts
+++ b/src/json-crdt/__demos__/toString-string.ts
@@ -31,7 +31,9 @@ console.log('Set initial string value:');
 console.log('');
 console.log(str.toString());
 
-str.api.str([]).ins(2, 'l').ins(10, '!');
+const strNode = str.api.str([]);
+strNode.ins(2, 'l');
+strNode.ins(10, '!');
 
 console.log('');
 console.log('After fixing errors in the string:');
diff --git a/src/json-expression/__bench__/main.ts b/src/json-expression/__bench__/main.ts
index 3114234808..9578573d63 100644
--- a/src/json-expression/__bench__/main.ts
+++ b/src/json-expression/__bench__/main.ts
@@ -50,12 +50,12 @@ const fn = codegen.run().compile();
 const suite = new Benchmark.Suite();
 suite
   .add(`json-joy/json-expression JsonExpressionCodegen`, () => {
-    fn({vars: new Vars(json)});
+    fn(new Vars(json));
   })
   .add(`json-joy/json-expression JsonExpressionCodegen with codegen`, () => {
     const codegen = new JsonExpressionCodegen({expression, operators: operatorsMap});
     const fn = codegen.run().compile();
-    fn({vars: new Vars(json)});
+    fn(new Vars(json));
   })
   .add(`json-joy/json-expression evaluate`, () => {
     evaluate(expression, {vars: new Vars(json)});