diff --git a/.mps/modules.xml b/.mps/modules.xml
index 0fc7c468..0de28061 100644
--- a/.mps/modules.xml
+++ b/.mps/modules.xml
@@ -14,6 +14,7 @@
       <modulePath path="$PROJECT_DIR$/typechecking/solutions/jetbrains.mps.typechecking.sample.test/jetbrains.mps.typechecking.sample.test.msd" folder="typechecking.test" />
       <modulePath path="$PROJECT_DIR$/typechecking/solutions/jetbrains.mps.typechecking.sample/jetbrains.mps.typechecking.sample.msd" folder="typechecking.test" />
       <modulePath path="$PROJECT_DIR$/typechecking/solutions/jetbrains.mps.typechecking.test/jetbrains.mps.lang.typechecking.test.msd" folder="typechecking.test" />
+      <modulePath path="$PROJECT_DIR$/typechecking/solutions/jetbrains.mps.typechecking.testlang.sandbox/jetbrains.mps.typechecking.testlang.sandbox.msd" folder="typechecking.test" />
       <modulePath path="$PROJECT_DIR$/typechecking/solutions/jetbrains.mps.typechecking.ui/jetbrains.mps.typechecking.ui.msd" folder="typechecking.ui" />
       <modulePath path="$PROJECT_DIR$/typechecking/solutions/jetbrains.mps.typechecking/jetbrains.mps.typechecking.msd" folder="typechecking" />
       <modulePath path="$PROJECT_DIR$/typesystem2/languages/jetbrains.mps.lang.smodel.types/jetbrains.mps.lang.smodel.types.mpl" folder="typesystem2" />
diff --git a/typechecking/languages/jetbrains.mps.typechecking.testlang/models/structure.mps b/typechecking/languages/jetbrains.mps.typechecking.testlang/models/structure.mps
index b02da773..a9c2723f 100644
--- a/typechecking/languages/jetbrains.mps.typechecking.testlang/models/structure.mps
+++ b/typechecking/languages/jetbrains.mps.typechecking.testlang/models/structure.mps
@@ -5,7 +5,64 @@
     <use id="c72da2b9-7cce-4447-8389-f407dc1158b7" name="jetbrains.mps.lang.structure" version="6" />
     <devkit ref="78434eb8-b0e5-444b-850d-e7c4ad2da9ab(jetbrains.mps.devkit.aspect.structure)" />
   </languages>
-  <imports />
-  <registry />
+  <imports>
+    <import index="tpck" ref="r:00000000-0000-4000-0000-011c89590288(jetbrains.mps.lang.core.structure)" implicit="true" />
+  </imports>
+  <registry>
+    <language id="c72da2b9-7cce-4447-8389-f407dc1158b7" name="jetbrains.mps.lang.structure">
+      <concept id="1169125787135" name="jetbrains.mps.lang.structure.structure.AbstractConceptDeclaration" flags="ig" index="PkWjJ">
+        <property id="6714410169261853888" name="conceptId" index="EcuMT" />
+        <property id="5092175715804935370" name="conceptAlias" index="34LRSv" />
+        <child id="1071489727083" name="linkDeclaration" index="1TKVEi" />
+      </concept>
+      <concept id="1071489090640" name="jetbrains.mps.lang.structure.structure.ConceptDeclaration" flags="ig" index="1TIwiD">
+        <property id="1096454100552" name="rootable" index="19KtqR" />
+        <reference id="1071489389519" name="extends" index="1TJDcQ" />
+      </concept>
+      <concept id="1071489288298" name="jetbrains.mps.lang.structure.structure.LinkDeclaration" flags="ig" index="1TJgyj">
+        <property id="1071599776563" name="role" index="20kJfa" />
+        <property id="1071599893252" name="sourceCardinality" index="20lbJX" />
+        <property id="1071599937831" name="metaClass" index="20lmBu" />
+        <property id="241647608299431140" name="linkId" index="IQ2ns" />
+        <reference id="1071599976176" name="target" index="20lvS9" />
+      </concept>
+    </language>
+    <language id="ceab5195-25ea-4f22-9b92-103b95ca8c0c" name="jetbrains.mps.lang.core">
+      <concept id="1169194658468" name="jetbrains.mps.lang.core.structure.INamedConcept" flags="ng" index="TrEIO">
+        <property id="1169194664001" name="name" index="TrG5h" />
+      </concept>
+    </language>
+  </registry>
+  <node concept="1TIwiD" id="7lt0LtPHOlU">
+    <property role="EcuMT" value="8456919074565735802" />
+    <property role="TrG5h" value="Container" />
+    <property role="19KtqR" value="true" />
+    <property role="34LRSv" value="Container" />
+    <ref role="1TJDcQ" to="tpck:gw2VY9q" resolve="BaseConcept" />
+    <node concept="1TJgyj" id="7lt0LtPHOme" role="1TKVEi">
+      <property role="IQ2ns" value="8456919074565735822" />
+      <property role="20lmBu" value="aggregation" />
+      <property role="20kJfa" value="statement" />
+      <property role="20lbJX" value="0..n" />
+      <ref role="20lvS9" node="7lt0LtPHOm6" resolve="Stmt" />
+    </node>
+  </node>
+  <node concept="1TIwiD" id="7lt0LtPHOm6">
+    <property role="EcuMT" value="8456919074565735814" />
+    <property role="TrG5h" value="Stmt" />
+    <ref role="1TJDcQ" to="tpck:gw2VY9q" resolve="BaseConcept" />
+    <node concept="1TJgyj" id="7lt0LtPHOmo" role="1TKVEi">
+      <property role="IQ2ns" value="8456919074565735832" />
+      <property role="20lmBu" value="aggregation" />
+      <property role="20kJfa" value="expression" />
+      <property role="20lbJX" value="0..n" />
+      <ref role="20lvS9" node="7lt0LtPHOmg" resolve="Expr" />
+    </node>
+  </node>
+  <node concept="1TIwiD" id="7lt0LtPHOmg">
+    <property role="EcuMT" value="8456919074565735824" />
+    <property role="TrG5h" value="Expr" />
+    <ref role="1TJDcQ" to="tpck:gw2VY9q" resolve="BaseConcept" />
+  </node>
 </model>
 
diff --git a/typechecking/languages/jetbrains.mps.typechecking.testlang/models/types.mps b/typechecking/languages/jetbrains.mps.typechecking.testlang/models/types.mps
index 9d8eff48..100fa0a1 100644
--- a/typechecking/languages/jetbrains.mps.typechecking.testlang/models/types.mps
+++ b/typechecking/languages/jetbrains.mps.typechecking.testlang/models/types.mps
@@ -9,6 +9,7 @@
     <import index="wyt6" ref="6354ebe7-c22a-4a0f-ac54-50b52ab9b065/java:java.lang(JDK/)" implicit="true" />
     <import index="tpck" ref="r:00000000-0000-4000-0000-011c89590288(jetbrains.mps.lang.core.structure)" implicit="true" />
     <import index="guwi" ref="6354ebe7-c22a-4a0f-ac54-50b52ab9b065/java:java.io(JDK/)" implicit="true" />
+    <import index="qulx" ref="r:ec0979fb-ae37-4823-9eaa-8550d9f5c6fd(jetbrains.mps.typechecking.testlang.structure)" implicit="true" />
   </imports>
   <registry>
     <language id="f3061a53-9226-4cc5-a443-f952ceaf5816" name="jetbrains.mps.baseLanguage">
@@ -29,6 +30,7 @@
       <concept id="1068431474542" name="jetbrains.mps.baseLanguage.structure.VariableDeclaration" flags="ng" index="33uBYm">
         <child id="1068431790190" name="initializer" index="33vP2m" />
       </concept>
+      <concept id="1068431790191" name="jetbrains.mps.baseLanguage.structure.Expression" flags="nn" index="33vP2n" />
       <concept id="1068498886296" name="jetbrains.mps.baseLanguage.structure.VariableReference" flags="nn" index="37vLTw">
         <reference id="1068581517664" name="variableDeclaration" index="3cqZAo" />
       </concept>
@@ -71,6 +73,11 @@
         <child id="1144230900587" name="variable" index="1Duv9x" />
       </concept>
     </language>
+    <language id="3a13115c-633c-4c5c-bbcc-75c4219e9555" name="jetbrains.mps.lang.quotation">
+      <concept id="1196350785113" name="jetbrains.mps.lang.quotation.structure.Quotation" flags="nn" index="2c44tf">
+        <child id="1196350785114" name="quotedNode" index="2c44tc" />
+      </concept>
+    </language>
     <language id="35320f26-77cb-4c55-be9f-a97a27770af1" name="jetbrains.mps.logic">
       <concept id="8169506320648805904" name="jetbrains.mps.logic.structure.LogicalVariableDeclarationContainer" flags="ng" index="29MRiA">
         <child id="3063948360254832884" name="declaration" index="3XD1gS" />
@@ -78,6 +85,7 @@
       <concept id="8829335963593820278" name="jetbrains.mps.logic.structure.LogicalVariable" flags="ng" index="a7P8L">
         <reference id="8829335963593822893" name="declaration" index="a7OzE" />
       </concept>
+      <concept id="8829335963591332101" name="jetbrains.mps.logic.structure.LogicalItem" flags="ng" index="aYkH2" />
       <concept id="8829335963591572611" name="jetbrains.mps.logic.structure.LogicalVariableDeclaration" flags="ng" index="aZer4" />
       <concept id="6856711987710888499" name="jetbrains.mps.logic.structure.TreeFormLiteral" flags="ng" index="Hz6ka">
         <child id="6856711987710888500" name="root" index="Hz6kd" />
@@ -86,6 +94,12 @@
         <property id="7571593955706137638" name="value" index="1oi5yK" />
       </concept>
     </language>
+    <language id="760a0a8c-eabb-4521-8bfd-65db761a9ba3" name="jetbrains.mps.baseLanguage.logging">
+      <concept id="1167227138527" name="jetbrains.mps.baseLanguage.logging.structure.LogStatement" flags="nn" index="34ab3g">
+        <property id="1167245565795" name="severity" index="35gtTG" />
+        <child id="1167227463056" name="logExpression" index="34bqiv" />
+      </concept>
+    </language>
     <language id="7866978e-a0f0-4cc7-81bc-4d213d9375e1" name="jetbrains.mps.lang.smodel">
       <concept id="1177026924588" name="jetbrains.mps.lang.smodel.structure.RefConcept_Reference" flags="nn" index="chp4Y">
         <reference id="1177026940964" name="conceptDeclaration" index="cht4Q" />
@@ -109,19 +123,37 @@
       </concept>
     </language>
     <language id="c4803b19-6d89-4a3b-bf82-390769514add" name="jetbrains.mps.lang.typesystem2">
+      <concept id="8456919074560454386" name="jetbrains.mps.lang.typesystem2.structure.ParameterContainer" flags="ng" index="0eUR_">
+        <child id="8456919074560454898" name="parameter" index="0eVf_" />
+      </concept>
+      <concept id="1618328391714701929" name="jetbrains.mps.lang.typesystem2.structure.TermTemplate" flags="ng" index="0oftK">
+        <child id="1618328391714701961" name="feature" index="0ofug" />
+      </concept>
+      <concept id="1618328391714701966" name="jetbrains.mps.lang.typesystem2.structure.ValueTermFeature" flags="ng" index="0ofun" />
+      <concept id="6086839168138086051" name="jetbrains.mps.lang.typesystem2.structure.TermTable" flags="ng" index="1HGPq">
+        <child id="6086839168138086052" name="termDeclaration" index="1HGPt" />
+      </concept>
       <concept id="4992889260816483106" name="jetbrains.mps.lang.typesystem2.structure.Condition" flags="ng" index="cBwPQ" />
       <concept id="6691972578451976398" name="jetbrains.mps.lang.typesystem2.structure.RuleInputSpecification" flags="ng" index="2t___k">
         <reference id="6691972578451990912" name="applicableConcept" index="2t_S0q" />
         <child id="6691972578451986151" name="input" index="2t_VXX" />
       </concept>
       <concept id="8335224865066015764" name="jetbrains.mps.lang.typesystem2.structure.Handler" flags="ng" index="AVZre">
+        <property id="2316688792951788157" name="stage" index="3J8TDj" />
         <child id="1980609059185345194" name="constraint" index="8PkJo" />
         <child id="3575255234175157601" name="template" index="1nK1Vg" />
       </concept>
+      <concept id="5524459797190399502" name="jetbrains.mps.lang.typesystem2.structure.TermDeclaration" flags="ng" index="BRKj$">
+        <child id="5524459797190401236" name="template" index="BRKSY" />
+      </concept>
+      <concept id="6856711987714624232" name="jetbrains.mps.lang.typesystem2.structure.ExpressionItem" flags="ng" index="HKQnh">
+        <child id="6856711987714624233" name="code" index="HKQng" />
+      </concept>
       <concept id="3575255234196628445" name="jetbrains.mps.lang.typesystem2.structure.RequireStatement" flags="ng" index="1mebxG">
         <child id="3575255234196628696" name="node" index="1mebXD" />
       </concept>
       <concept id="3575255234174969639" name="jetbrains.mps.lang.typesystem2.structure.ConstraintRule" flags="ng" index="1nLNMm">
+        <child id="8456919074565751439" name="parameter" index="0UC6o" />
         <child id="3575255234174969658" name="head" index="1nLNMb" />
         <child id="3575255234174969660" name="body" index="1nLNMd" />
       </concept>
@@ -138,6 +170,10 @@
       <concept id="7368070394769139970" name="jetbrains.mps.lang.typesystem2.structure.RuleInputReference" flags="ng" index="3A2sRY">
         <reference id="7368070394769213644" name="declaration" index="3A2yKK" />
       </concept>
+      <concept id="7368070394770780974" name="jetbrains.mps.lang.typesystem2.structure.UnifiesConstraint" flags="ng" index="3A8Hvi">
+        <child id="7368070394770793930" name="value" index="3A8w4Q" />
+        <child id="7368070394770793388" name="assignee" index="3A8wtg" />
+      </concept>
       <concept id="7368070394766963750" name="jetbrains.mps.lang.typesystem2.structure.Head" flags="ng" index="3Aq93q">
         <property id="7368070394767443940" name="keep" index="3ArMco" />
       </concept>
@@ -159,9 +195,14 @@
       <concept id="1476354154047570702" name="jetbrains.mps.lang.typesystem2.structure.CodeBlock" flags="ng" index="3AO9d9">
         <child id="535508562359074271" name="code" index="16YjZG" />
       </concept>
+      <concept id="1476354154047290768" name="jetbrains.mps.lang.typesystem2.structure.GetterBlock" flags="ng" index="3AP2Rn" />
       <concept id="8581119423153238082" name="jetbrains.mps.lang.typesystem2.structure.NodeAnchor" flags="ng" index="3BlFb$">
         <child id="8581119423153238083" name="node" index="3BlFb_" />
       </concept>
+      <concept id="1877115349178398764" name="jetbrains.mps.lang.typesystem2.structure.EqualsConstraint" flags="ng" index="3GeI9q">
+        <child id="1877115349178398815" name="right" index="3GeI8D" />
+        <child id="1877115349178398813" name="left" index="3GeI8F" />
+      </concept>
       <concept id="2316688792938826204" name="jetbrains.mps.lang.typesystem2.structure.ConstraintLogicalClause" flags="ng" index="3I6s7M">
         <child id="2316688792938826214" name="constraint" index="3I6s78" />
       </concept>
@@ -172,6 +213,14 @@
         <child id="2316688792939428590" name="code" index="3IrJb0" />
       </concept>
       <concept id="965748826975413063" name="jetbrains.mps.lang.typesystem2.structure.RulePartParameterDeclaration" flags="ng" index="3NuqgR" />
+      <concept id="2037618519496446007" name="jetbrains.mps.lang.typesystem2.structure.Term" flags="ng" index="1Q4cc8">
+        <reference id="6086839168126957156" name="termDecl" index="1nfQt" />
+        <child id="2037618519520915633" name="override" index="1Ryyee" />
+      </concept>
+      <concept id="2037618519520719251" name="jetbrains.mps.lang.typesystem2.structure.TermFeatureOverride" flags="ng" index="1RziaG">
+        <reference id="2037618519520719300" name="feature" index="1RzibV" />
+        <child id="2037618519520739064" name="term" index="1RzmR7" />
+      </concept>
       <concept id="3063948360252660075" name="jetbrains.mps.lang.typesystem2.structure.TypeofConstraint" flags="ng" index="3XxkQB">
         <child id="3063948360252667312" name="assignedType" index="3Xxm5W" />
         <child id="3063948360252666228" name="anchor" index="3XxmmS" />
@@ -380,5 +429,198 @@
       </node>
     </node>
   </node>
+  <node concept="AVZre" id="7lt0LtPHRYY">
+    <property role="TrG5h" value="Type" />
+    <node concept="1nLNMY" id="7lt0LtPHRZ8" role="1nK1Vg">
+      <property role="TrG5h" value="exprTypeof" />
+      <node concept="3clFbS" id="7lt0LtPHRZ9" role="1nLNMH">
+        <node concept="34ab3g" id="7lt0LtPNFE0" role="3cqZAp">
+          <property role="35gtTG" value="error" />
+          <node concept="Xl_RD" id="7lt0LtPNFE2" role="34bqiv">
+            <property role="Xl_RC" value="****" />
+          </node>
+        </node>
+        <node concept="3clFbH" id="7lt0LtPNFFp" role="3cqZAp" />
+        <node concept="1nLNNL" id="7lt0LtPHRZ_" role="3cqZAp">
+          <node concept="1nLNMm" id="7lt0LtPHRZA" role="1nLNNK">
+            <node concept="3Aq9E8" id="7lt0LtPHRZD" role="1nLNMd">
+              <node concept="3I6sU6" id="7lt0LtPHRZE" role="3Ip0Jz">
+                <node concept="3I6s7M" id="7lt0LtPHS0f" role="3I6sU7">
+                  <node concept="3A8Hvi" id="7lt0LtPHS09" role="3I6s78">
+                    <node concept="a7P8L" id="7lt0LtPIYZ7" role="3A8wtg">
+                      <ref role="a7OzE" node="7lt0LtPIm0Y" resolve="T" />
+                    </node>
+                    <node concept="1Q4cc8" id="7lt0LtPIZ7_" role="3A8w4Q">
+                      <ref role="1nfQt" node="7lt0LtPIZ7a" resolve="Foo" />
+                      <node concept="1RziaG" id="7lt0LtPIZ7B" role="1Ryyee">
+                        <ref role="1RzibV" node="7lt0LtPIZ7g" resolve="bar" />
+                        <node concept="3AP2Rn" id="7lt0LtPIZ7C" role="1RzmR7">
+                          <node concept="3clFbS" id="7lt0LtPIZ7D" role="16YjZG">
+                            <node concept="3clFbF" id="7lt0LtPIZ7R" role="3cqZAp">
+                              <node concept="Xl_RD" id="7lt0LtPIZ7Q" role="3clFbG">
+                                <property role="Xl_RC" value="BLAHBLAH" />
+                              </node>
+                            </node>
+                          </node>
+                        </node>
+                      </node>
+                    </node>
+                  </node>
+                </node>
+                <node concept="3I6s7M" id="7lt0LtPHRZL" role="3I6sU7">
+                  <node concept="3XxkQB" id="7lt0LtPHRZH" role="3I6s78">
+                    <node concept="3BlFb$" id="7lt0LtPHRZI" role="3XxmmS">
+                      <node concept="3A2sRY" id="7lt0LtPHRZU" role="3BlFb_">
+                        <ref role="3A2yKK" node="7lt0LtPHRZd" resolve="expr" />
+                      </node>
+                    </node>
+                    <node concept="a7P8L" id="7lt0LtPIZce" role="3Xxm5W">
+                      <ref role="a7OzE" node="7lt0LtPIm0Y" resolve="T" />
+                    </node>
+                  </node>
+                </node>
+              </node>
+            </node>
+            <node concept="3Aq93q" id="7lt0LtPHS0p" role="1nLNMb">
+              <property role="3ArMco" value="true" />
+              <node concept="3I6sU6" id="7lt0LtPHS0q" role="3Ip0Jz">
+                <node concept="3I6s7M" id="7lt0LtPPJ7D" role="3I6sU7">
+                  <node concept="3XxkQB" id="7lt0LtPPJ7_" role="3I6s78">
+                    <node concept="3BlFb$" id="7lt0LtPPJ7A" role="3XxmmS">
+                      <node concept="3A2sRY" id="7lt0LtPQXdC" role="3BlFb_">
+                        <ref role="3A2yKK" node="7lt0LtPHRZd" resolve="expr" />
+                      </node>
+                    </node>
+                    <node concept="a7P8L" id="7lt0LtPQXdK" role="3Xxm5W">
+                      <ref role="a7OzE" node="7lt0LtPIm0Y" resolve="T" />
+                    </node>
+                  </node>
+                </node>
+              </node>
+            </node>
+            <node concept="0eUR_" id="7lt0LtPIm0V" role="0UC6o">
+              <node concept="3NuqgR" id="7lt0LtPIm0X" role="0eVf_">
+                <node concept="aZer4" id="7lt0LtPIm0Y" role="3XD1gS">
+                  <property role="TrG5h" value="T" />
+                </node>
+              </node>
+            </node>
+          </node>
+        </node>
+      </node>
+      <node concept="2t___k" id="7lt0LtPHRZc" role="1nLNMg">
+        <ref role="2t_S0q" to="qulx:7lt0LtPHOmg" resolve="Expr" />
+        <node concept="3A20r5" id="7lt0LtPHRZd" role="2t_VXX">
+          <property role="TrG5h" value="expr" />
+        </node>
+      </node>
+    </node>
+  </node>
+  <node concept="1HGPq" id="7lt0LtPIZ79">
+    <property role="TrG5h" value="Types" />
+    <node concept="BRKj$" id="7lt0LtPIZ7a" role="1HGPt">
+      <property role="TrG5h" value="Foo" />
+      <node concept="0oftK" id="7lt0LtPIZ7b" role="BRKSY">
+        <node concept="0ofun" id="7lt0LtPIZ7g" role="0ofug">
+          <property role="TrG5h" value="bar" />
+        </node>
+      </node>
+    </node>
+  </node>
+  <node concept="AVZre" id="7lt0LtPOZVe">
+    <property role="3J8TDj" value="recover" />
+    <property role="TrG5h" value="Recover" />
+    <node concept="3AqmO8" id="7lt0LtPOZVl" role="8PkJo">
+      <property role="TrG5h" value="recover" />
+    </node>
+    <node concept="3AqmO8" id="7lt0LtPOZWJ" role="8PkJo">
+      <property role="TrG5h" value="typeNode" />
+      <node concept="1zAUYm" id="7lt0LtPP10G" role="1zAUyy">
+        <property role="TrG5h" value="node" />
+      </node>
+      <node concept="1zAUYm" id="7lt0LtPP10I" role="1zAUyy">
+        <property role="TrG5h" value="expression" />
+      </node>
+    </node>
+    <node concept="1nLNMY" id="7lt0LtPOZVh" role="1nK1Vg">
+      <property role="TrG5h" value="recoverExpr" />
+      <node concept="3clFbS" id="7lt0LtPOZVi" role="1nLNMH">
+        <node concept="1nLNNL" id="7lt0LtPOZW0" role="3cqZAp">
+          <node concept="1nLNMm" id="7lt0LtPOZW1" role="1nLNNK">
+            <node concept="0eUR_" id="7lt0LtPOZW5" role="0UC6o">
+              <node concept="3NuqgR" id="7lt0LtPOZW7" role="0eVf_">
+                <node concept="aZer4" id="7lt0LtPOZW8" role="3XD1gS">
+                  <property role="TrG5h" value="T" />
+                </node>
+                <node concept="aZer4" id="7lt0LtPP29U" role="3XD1gS">
+                  <property role="TrG5h" value="Node" />
+                </node>
+              </node>
+            </node>
+            <node concept="3Aq9E8" id="7lt0LtPP11l" role="1nLNMd">
+              <node concept="3I6sU6" id="7lt0LtPP11m" role="3Ip0Jz">
+                <node concept="3I6s7M" id="7lt0LtPP29M" role="3I6sU7">
+                  <node concept="3GeI9q" id="7lt0LtPP29G" role="3I6s78">
+                    <node concept="a7P8L" id="7lt0LtPP2ab" role="3GeI8F">
+                      <ref role="a7OzE" node="7lt0LtPP29U" resolve="Node" />
+                    </node>
+                    <node concept="HKQnh" id="7lt0LtPP2an" role="3GeI8D">
+                      <node concept="2c44tf" id="7lt0LtPP2as" role="HKQng">
+                        <node concept="17QB3L" id="7lt0LtPP2aI" role="2c44tc" />
+                      </node>
+                    </node>
+                  </node>
+                </node>
+                <node concept="3I6s7M" id="7lt0LtPP11q" role="3I6sU7">
+                  <node concept="3Aqt3T" id="7lt0LtPP11p" role="3I6s78">
+                    <ref role="3AqCNq" node="7lt0LtPOZWJ" resolve="typeNode" />
+                    <node concept="a7P8L" id="7lt0LtPP2b1" role="3AunhB">
+                      <ref role="a7OzE" node="7lt0LtPP29U" resolve="Node" />
+                    </node>
+                    <node concept="3BlFb$" id="7lt0LtPP2b7" role="3AunhB">
+                      <node concept="3A2sRY" id="7lt0LtPP2bh" role="3BlFb_">
+                        <ref role="3A2yKK" node="7lt0LtPOZVo" resolve="expr" />
+                      </node>
+                    </node>
+                  </node>
+                </node>
+              </node>
+            </node>
+            <node concept="3Aq93q" id="7lt0LtPPf70" role="1nLNMb">
+              <node concept="3I6sU6" id="7lt0LtPPf71" role="3Ip0Jz">
+                <node concept="3I6s7M" id="7lt0LtPPig$" role="3I6sU7">
+                  <node concept="3XxkQB" id="7lt0LtPPigw" role="3I6s78">
+                    <node concept="3BlFb$" id="7lt0LtPPigx" role="3XxmmS">
+                      <node concept="33vP2n" id="7lt0LtPPigy" role="3BlFb_" />
+                    </node>
+                    <node concept="aYkH2" id="7lt0LtPPigz" role="3Xxm5W" />
+                  </node>
+                </node>
+              </node>
+            </node>
+            <node concept="3Aq93q" id="7lt0LtPPfsJ" role="1nLNMb">
+              <property role="3ArMco" value="true" />
+              <node concept="3I6sU6" id="7lt0LtPPfsK" role="3Ip0Jz">
+                <node concept="3I6s7M" id="7lt0LtPPfPv" role="3I6sU7">
+                  <node concept="3Aqt3T" id="7lt0LtPPfPu" role="3I6s78">
+                    <ref role="3AqCNq" node="36tQV5ADNk_" resolve="bar" />
+                    <node concept="a7P8L" id="7lt0LtPPfP_" role="3AunhB">
+                      <ref role="a7OzE" node="7lt0LtPOZW8" resolve="T" />
+                    </node>
+                  </node>
+                </node>
+              </node>
+            </node>
+          </node>
+        </node>
+      </node>
+      <node concept="2t___k" id="7lt0LtPOZVn" role="1nLNMg">
+        <ref role="2t_S0q" to="qulx:7lt0LtPHOmg" resolve="Expr" />
+        <node concept="3A20r5" id="7lt0LtPOZVo" role="2t_VXX">
+          <property role="TrG5h" value="expr" />
+        </node>
+      </node>
+    </node>
+  </node>
 </model>
 
diff --git a/typechecking/solutions/jetbrains.mps.typechecking.testlang.sandbox/jetbrains.mps.typechecking.testlang.sandbox.msd b/typechecking/solutions/jetbrains.mps.typechecking.testlang.sandbox/jetbrains.mps.typechecking.testlang.sandbox.msd
new file mode 100644
index 00000000..fccf7913
--- /dev/null
+++ b/typechecking/solutions/jetbrains.mps.typechecking.testlang.sandbox/jetbrains.mps.typechecking.testlang.sandbox.msd
@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<solution name="jetbrains.mps.typechecking.testlang.sandbox" uuid="f9bad4b1-59da-4f20-8feb-9f4cc4ad872e" moduleVersion="0" compileInMPS="true">
+  <models>
+    <modelRoot contentPath="${module}" type="default">
+      <sourceRoot location="models" />
+    </modelRoot>
+  </models>
+  <sourcePath />
+  <dependencies>
+    <dependency reexport="false">3a1f0f04-b5e0-43be-884e-b856bfdeca21(jetbrains.mps.typechecking.testlang)</dependency>
+  </dependencies>
+  <languageVersions>
+    <language slang="l:ceab5195-25ea-4f22-9b92-103b95ca8c0c:jetbrains.mps.lang.core" version="1" />
+    <language slang="l:3a1f0f04-b5e0-43be-884e-b856bfdeca21:jetbrains.mps.typechecking.testlang" version="0" />
+  </languageVersions>
+  <dependencyVersions>
+    <module reference="3f233e7f-b8a6-46d2-a57f-795d56775243(Annotations)" version="0" />
+    <module reference="6354ebe7-c22a-4a0f-ac54-50b52ab9b065(JDK)" version="0" />
+    <module reference="6ed54515-acc8-4d1e-a16c-9fd6cfe951ea(MPS.Core)" version="0" />
+    <module reference="8865b7a8-5271-43d3-884c-6fd1d9cfdd34(MPS.OpenAPI)" version="0" />
+    <module reference="ceab5195-25ea-4f22-9b92-103b95ca8c0c(jetbrains.mps.lang.core)" version="0" />
+    <module reference="d7eb0a2a-bd50-4576-beae-e4a89db35f20(jetbrains.mps.lang.scopes.runtime)" version="0" />
+    <module reference="c72da2b9-7cce-4447-8389-f407dc1158b7(jetbrains.mps.lang.structure)" version="0" />
+    <module reference="3a1f0f04-b5e0-43be-884e-b856bfdeca21(jetbrains.mps.typechecking.testlang)" version="0" />
+    <module reference="f9bad4b1-59da-4f20-8feb-9f4cc4ad872e(jetbrains.mps.typechecking.testlang.sandbox)" version="0" />
+  </dependencyVersions>
+</solution>
+
diff --git a/typechecking/solutions/jetbrains.mps.typechecking.testlang.sandbox/models/test.mps b/typechecking/solutions/jetbrains.mps.typechecking.testlang.sandbox/models/test.mps
new file mode 100644
index 00000000..c0bd6a31
--- /dev/null
+++ b/typechecking/solutions/jetbrains.mps.typechecking.testlang.sandbox/models/test.mps
@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<model ref="r:0e60ac07-77c3-4d5c-b40d-73e8fd128592(jetbrains.mps.typechecking.testlang.sandbox.test)">
+  <persistence version="9" />
+  <languages>
+    <use id="3a1f0f04-b5e0-43be-884e-b856bfdeca21" name="jetbrains.mps.typechecking.testlang" version="0" />
+  </languages>
+  <imports />
+  <registry>
+    <language id="3a1f0f04-b5e0-43be-884e-b856bfdeca21" name="jetbrains.mps.typechecking.testlang">
+      <concept id="8456919074565735802" name="jetbrains.mps.typechecking.testlang.structure.Container" flags="ng" index="0U$pH">
+        <child id="8456919074565735822" name="statement" index="0U$qp" />
+      </concept>
+      <concept id="8456919074565735824" name="jetbrains.mps.typechecking.testlang.structure.Expr" flags="ng" index="0U$q7" />
+      <concept id="8456919074565735814" name="jetbrains.mps.typechecking.testlang.structure.Stmt" flags="ng" index="0U$qh">
+        <child id="8456919074565735832" name="expression" index="0U$qf" />
+      </concept>
+    </language>
+  </registry>
+  <node concept="0U$pH" id="7lt0LtPHRY$">
+    <node concept="0U$qh" id="7lt0LtPHRYI" role="0U$qp">
+      <node concept="0U$q7" id="7lt0LtPHRYK" role="0U$qf" />
+      <node concept="0U$q7" id="7lt0LtPHRYM" role="0U$qf" />
+      <node concept="0U$q7" id="7lt0LtPHRYP" role="0U$qf" />
+      <node concept="0U$q7" id="7lt0LtPHRYT" role="0U$qf" />
+    </node>
+  </node>
+</model>
+