diff --git a/samples/lambdacalc/languages/sample.fooblin/models/behavior.mps b/samples/lambdacalc/languages/sample.fooblin/models/behavior.mps
index 2752f247..acab5f73 100644
--- a/samples/lambdacalc/languages/sample.fooblin/models/behavior.mps
+++ b/samples/lambdacalc/languages/sample.fooblin/models/behavior.mps
@@ -172,6 +172,7 @@
         <child id="6039268229364358387" name="concept" index="1pnPq6" />
       </concept>
       <concept id="1172008320231" name="jetbrains.mps.lang.smodel.structure.Node_IsNotNullOperation" flags="nn" index="3x8VRR" />
+      <concept id="1144100932627" name="jetbrains.mps.lang.smodel.structure.OperationParm_Inclusion" flags="ng" index="1xIGOp" />
       <concept id="1144101972840" name="jetbrains.mps.lang.smodel.structure.OperationParm_Concept" flags="ng" index="1xMEDy">
         <child id="1207343664468" name="conceptArgument" index="ri$Ld" />
       </concept>
@@ -207,7 +208,7 @@
         <child id="540871147943773366" name="argument" index="25WWJ7" />
       </concept>
       <concept id="1203518072036" name="jetbrains.mps.baseLanguage.collections.structure.SmartClosureParameterDeclaration" flags="ig" index="Rh6nW" />
-      <concept id="1160612413312" name="jetbrains.mps.baseLanguage.collections.structure.AddElementOperation" flags="nn" index="TSZUe" />
+      <concept id="1160666733551" name="jetbrains.mps.baseLanguage.collections.structure.AddAllElementsOperation" flags="nn" index="X8dFx" />
       <concept id="1225727723840" name="jetbrains.mps.baseLanguage.collections.structure.FindFirstOperation" flags="nn" index="1z4cxt" />
     </language>
   </registry>
@@ -312,6 +313,7 @@
                               <ref role="cht4Q" to="8tt8:7_8aRkgDGPo" resolve="Var" />
                             </node>
                           </node>
+                          <node concept="1xIGOp" id="G788z3p1Is" role="1xVPHs" />
                         </node>
                       </node>
                       <node concept="37vLTw" id="4rRw8_AuDEM" role="37vLTJ">
@@ -330,17 +332,22 @@
                   <node concept="3clFbF" id="6ydDNpmN6Uc" role="3cqZAp">
                     <node concept="37vLTI" id="6ydDNpmN6Ud" role="3clFbG">
                       <node concept="2OqwBi" id="6ydDNpmN6Ue" role="37vLTx">
-                        <node concept="2OqwBi" id="6ydDNpmN6Uf" role="2Oq$k0">
-                          <node concept="1PxgMI" id="6ydDNpmN6Ug" role="2Oq$k0">
-                            <node concept="37vLTw" id="6ydDNpmN6Uh" role="1m5AlR">
-                              <ref role="3cqZAo" node="4rRw8_AuAJD" resolve="binder" />
+                        <node concept="2OqwBi" id="G788z3oDRt" role="2Oq$k0">
+                          <node concept="2OqwBi" id="6ydDNpmN6Uf" role="2Oq$k0">
+                            <node concept="1PxgMI" id="6ydDNpmN6Ug" role="2Oq$k0">
+                              <node concept="37vLTw" id="6ydDNpmN6Uh" role="1m5AlR">
+                                <ref role="3cqZAo" node="4rRw8_AuAJD" resolve="binder" />
+                              </node>
+                              <node concept="chp4Y" id="4i_CItPT6Ql" role="3oSUPX">
+                                <ref role="cht4Q" to="8tt8:7_8aRkgDGQo" resolve="LetExpr" />
+                              </node>
                             </node>
-                            <node concept="chp4Y" id="4i_CItPT6Ql" role="3oSUPX">
-                              <ref role="cht4Q" to="8tt8:7_8aRkgDGQo" resolve="LetExpr" />
+                            <node concept="3TrEf2" id="6ydDNpmN7zR" role="2OqNvi">
+                              <ref role="3Tt5mk" to="8tt8:7_8aRkgDGQv" resolve="bind" />
                             </node>
                           </node>
-                          <node concept="3TrEf2" id="6ydDNpmN7zR" role="2OqNvi">
-                            <ref role="3Tt5mk" to="8tt8:7_8aRkgDGQv" resolve="bind" />
+                          <node concept="3TrEf2" id="G788z3oE5I" role="2OqNvi">
+                            <ref role="3Tt5mk" to="8tt8:7_8aRkgDGQq" resolve="left" />
                           </node>
                         </node>
                         <node concept="2Rf3mk" id="6ydDNpmN6Uj" role="2OqNvi">
@@ -349,6 +356,7 @@
                               <ref role="cht4Q" to="8tt8:7_8aRkgDGPo" resolve="Var" />
                             </node>
                           </node>
+                          <node concept="1xIGOp" id="G788z3p1_6" role="1xVPHs" />
                         </node>
                       </node>
                       <node concept="37vLTw" id="6ydDNpmN6Um" role="37vLTJ">
@@ -378,37 +386,12 @@
                       </node>
                     </node>
                   </node>
-                  <node concept="3clFbF" id="6ydDNpmM0uT" role="3cqZAp">
-                    <node concept="2OqwBi" id="6ydDNpmM2ec" role="3clFbG">
-                      <node concept="37vLTw" id="6ydDNpmM0uR" role="2Oq$k0">
-                        <ref role="3cqZAo" node="4rRw8_AuDnU" resolve="allBound" />
-                      </node>
-                      <node concept="TSZUe" id="6ydDNpmNfGj" role="2OqNvi">
-                        <node concept="2OqwBi" id="6ydDNpmNfGm" role="25WWJ7">
-                          <node concept="1PxgMI" id="6ydDNpmNfGn" role="2Oq$k0">
-                            <node concept="37vLTw" id="6ydDNpmNfGo" role="1m5AlR">
-                              <ref role="3cqZAo" node="4rRw8_AuAJD" resolve="binder" />
-                            </node>
-                            <node concept="chp4Y" id="4i_CItPT6Qn" role="3oSUPX">
-                              <ref role="cht4Q" to="8tt8:7_8aRkgDHAe" resolve="LetClause" />
-                            </node>
-                          </node>
-                          <node concept="3TrEf2" id="6ydDNpmNhjU" role="2OqNvi">
-                            <ref role="3Tt5mk" to="8tt8:7_8aRkgDHAf" resolve="var" />
-                          </node>
-                        </node>
-                      </node>
-                    </node>
-                  </node>
                   <node concept="3cpWs8" id="6ydDNpmMcOj" role="3cqZAp">
                     <node concept="3cpWsn" id="6ydDNpmMcOk" role="3cpWs9">
                       <property role="TrG5h" value="prevSibling" />
                       <node concept="3Tqbb2" id="6ydDNpmMcOg" role="1tU5fm" />
-                      <node concept="2OqwBi" id="6ydDNpmMcOl" role="33vP2m">
-                        <node concept="37vLTw" id="6ydDNpmMcOm" role="2Oq$k0">
-                          <ref role="3cqZAo" node="4rRw8_AuAJD" resolve="binder" />
-                        </node>
-                        <node concept="YBYNd" id="6ydDNpmMcOn" role="2OqNvi" />
+                      <node concept="37vLTw" id="6ydDNpmMcOm" role="33vP2m">
+                        <ref role="3cqZAo" node="4rRw8_AuAJD" resolve="binder" />
                       </node>
                     </node>
                   </node>
@@ -566,23 +549,33 @@
               <ref role="3gnhBz" to="8tt8:7_8aRkgDHAe" resolve="LetClause" />
             </node>
             <node concept="3clFbS" id="6ydDNpmNLsH" role="1pnPq1">
-              <node concept="3clFbF" id="6ydDNpmNLsI" role="3cqZAp">
-                <node concept="2OqwBi" id="6ydDNpmNLsJ" role="3clFbG">
-                  <node concept="37vLTw" id="6ydDNpmNLsK" role="2Oq$k0">
+              <node concept="3clFbF" id="G788z3pc8y" role="3cqZAp">
+                <node concept="2OqwBi" id="G788z3pc8z" role="3clFbG">
+                  <node concept="37vLTw" id="G788z3pc8$" role="2Oq$k0">
                     <ref role="3cqZAo" node="6ydDNpmNLpP" resolve="allBound" />
                   </node>
-                  <node concept="TSZUe" id="6ydDNpmNLsL" role="2OqNvi">
-                    <node concept="2OqwBi" id="6ydDNpmNLsM" role="25WWJ7">
-                      <node concept="1PxgMI" id="6ydDNpmNLsN" role="2Oq$k0">
-                        <node concept="37vLTw" id="6ydDNpmNM0d" role="1m5AlR">
-                          <ref role="3cqZAo" node="6ydDNpmNLrk" resolve="clause" />
+                  <node concept="X8dFx" id="G788z3pc8_" role="2OqNvi">
+                    <node concept="2OqwBi" id="G788z3pc8A" role="25WWJ7">
+                      <node concept="2OqwBi" id="G788z3pc8B" role="2Oq$k0">
+                        <node concept="1PxgMI" id="G788z3pc8C" role="2Oq$k0">
+                          <node concept="37vLTw" id="G788z3pe3X" role="1m5AlR">
+                            <ref role="3cqZAo" node="6ydDNpmNLrk" resolve="clause" />
+                          </node>
+                          <node concept="chp4Y" id="G788z3pc8E" role="3oSUPX">
+                            <ref role="cht4Q" to="8tt8:7_8aRkgDHAe" resolve="LetClause" />
+                          </node>
                         </node>
-                        <node concept="chp4Y" id="4i_CItPT6Qm" role="3oSUPX">
-                          <ref role="cht4Q" to="8tt8:7_8aRkgDHAe" resolve="LetClause" />
+                        <node concept="3TrEf2" id="G788z3pc8F" role="2OqNvi">
+                          <ref role="3Tt5mk" to="8tt8:7_8aRkgDHAf" resolve="var" />
                         </node>
                       </node>
-                      <node concept="3TrEf2" id="6ydDNpmNLsP" role="2OqNvi">
-                        <ref role="3Tt5mk" to="8tt8:7_8aRkgDHAf" resolve="var" />
+                      <node concept="2Rf3mk" id="G788z3pc8G" role="2OqNvi">
+                        <node concept="1xMEDy" id="G788z3pc8H" role="1xVPHs">
+                          <node concept="chp4Y" id="G788z3pc8I" role="ri$Ld">
+                            <ref role="cht4Q" to="8tt8:7_8aRkgDGPo" resolve="Var" />
+                          </node>
+                        </node>
+                        <node concept="1xIGOp" id="G788z3pc8J" role="1xVPHs" />
                       </node>
                     </node>
                   </node>
diff --git a/samples/lambdacalc/languages/sample.fooblin/models/structure.mps b/samples/lambdacalc/languages/sample.fooblin/models/structure.mps
index 511b58c3..5b122aa9 100644
--- a/samples/lambdacalc/languages/sample.fooblin/models/structure.mps
+++ b/samples/lambdacalc/languages/sample.fooblin/models/structure.mps
@@ -214,7 +214,7 @@
       <property role="20lmBu" value="aggregation" />
       <property role="20kJfa" value="var" />
       <property role="20lbJX" value="1" />
-      <ref role="20lvS9" node="7_8aRkgDGPo" resolve="Var" />
+      <ref role="20lvS9" node="7_8aRkgDGPJ" resolve="Expr" />
     </node>
     <node concept="1TJgyj" id="7_8aRkgDHAh" role="1TKVEi">
       <property role="IQ2ns" value="8739282858702985617" />
diff --git a/samples/lambdacalc/languages/sample.fooblin/models/types.mps b/samples/lambdacalc/languages/sample.fooblin/models/types.mps
index 877387b0..d8fec80f 100644
--- a/samples/lambdacalc/languages/sample.fooblin/models/types.mps
+++ b/samples/lambdacalc/languages/sample.fooblin/models/types.mps
@@ -1292,6 +1292,58 @@
         </node>
       </node>
     </node>
+    <node concept="AVZhu" id="G788z3oS9$" role="3ArX_J">
+      <property role="TrG5h" value="typeOf_LetExpr" />
+      <node concept="3Aq9E8" id="G788z3oTvD" role="3otmyu">
+        <node concept="3I6sU6" id="G788z3oTvE" role="3Ip0Jz">
+          <node concept="3I6s7M" id="G788z3oTvL" role="3I6sU7">
+            <node concept="3XxkQB" id="G788z3oTvH" role="3I6s78">
+              <node concept="aYllk" id="G788z3oTvI" role="3XxmmS">
+                <node concept="3A2sRY" id="G788z3oTvU" role="aYrYs">
+                  <ref role="3A2yKK" node="G788z3oSpi" resolve="let" />
+                </node>
+              </node>
+              <node concept="a7P8L" id="G788z3oTw2" role="3Xxm5W">
+                <ref role="a7OzE" node="G788z3oSpw" resolve="E" />
+              </node>
+            </node>
+          </node>
+        </node>
+      </node>
+      <node concept="3Aq93q" id="G788z3oSpr" role="3orSU4">
+        <property role="3ArMco" value="true" />
+        <node concept="3NuqgR" id="G788z3oSpv" role="3Nuqhd">
+          <node concept="aZer4" id="G788z3oSpw" role="3XD1gS">
+            <property role="TrG5h" value="E" />
+          </node>
+        </node>
+        <node concept="3I6sU6" id="G788z3oSps" role="3Ip0Jz">
+          <node concept="3I6s7M" id="G788z3oTaY" role="3I6sU7">
+            <node concept="3XxkQB" id="G788z3oTaU" role="3I6s78">
+              <node concept="aYllk" id="G788z3oTaV" role="3XxmmS">
+                <node concept="2OqwBi" id="G788z3oTiI" role="aYrYs">
+                  <node concept="3A2sRY" id="G788z3oTb7" role="2Oq$k0">
+                    <ref role="3A2yKK" node="G788z3oSpi" resolve="let" />
+                  </node>
+                  <node concept="3TrEf2" id="G788z3oTtu" role="2OqNvi">
+                    <ref role="3Tt5mk" to="8tt8:7_8aRkgDGQx" resolve="expr" />
+                  </node>
+                </node>
+              </node>
+              <node concept="a7P8L" id="G788z3oTv$" role="3Xxm5W">
+                <ref role="a7OzE" node="G788z3oSpw" resolve="E" />
+              </node>
+            </node>
+          </node>
+        </node>
+      </node>
+      <node concept="2t___k" id="G788z3oSph" role="20_v8_">
+        <ref role="2t_S0q" to="8tt8:7_8aRkgDGQo" resolve="LetExpr" />
+        <node concept="3A20r5" id="G788z3oSpi" role="2t_VXX">
+          <property role="TrG5h" value="let" />
+        </node>
+      </node>
+    </node>
     <node concept="AVZhu" id="4rRw8_Avlkw" role="3ArX_J">
       <property role="TrG5h" value="typeOf_LetClause" />
       <node concept="3Aq93q" id="4rRw8_Avls4" role="3orSU4">