work on #2683

src/org/rascalmpl/interpreter/Evaluator.java

@@ -1175,9 +1175,8 @@ private void reloadModules(IRascalMonitor monitor, Set<String> names, ISourceLoc
             for (String mod : names) {
                 if (heap.existsModule(mod)) {
                     var uri = heap.getModuleURI(mod);
-                    assert uri != null : "guaranteed by Import::loadModule";
-
-                    if (resolverRegistry.exists(vf.sourceLocation(uri))) {
+
+                    if (mod.equals(ModuleEnvironment.SHELL_MODULE) || resolverRegistry.exists(vf.sourceLocation(uri))) {
                         // otherwise the file has been renamed or deleted, and we do
                         // not add it to the todo list.
                         onHeap.add(mod);
@@ -1189,8 +1188,10 @@ private void reloadModules(IRascalMonitor monitor, Set<String> names, ISourceLoc
                         extendingModules.addAll(heap.getExtendingModules(mod));
                     }
 
-                    // this module starts with a clean slate
-                    heap.removeModule(heap.getModule(mod));
+                    if (!mod.equals(ModuleEnvironment.SHELL_MODULE)) {
+                        // this module starts with a clean slate
+                        heap.removeModule(heap.getModule(mod));
+                    }
                 }
             }
 
@@ -1324,7 +1325,7 @@ private Set<String> getExtendingModules(Set<String> names) {
             found.addAll(dependingModules);
             todo.addAll(dependingModules);
         }
-
+        
         return found;
     }
 

src/org/rascalmpl/semantics/dynamic/Import.java

@@ -197,7 +197,15 @@ public Extend(ISourceLocation src, IConstructor node, ImportedModule module) {
 		@Override
 		public Result<IValue> interpret(IEvaluator<Result<IValue>> eval) {
 			String name = Names.fullName(this.getModule().getName());
-      extendCurrentModule(this.getLocation(), name, eval);
+
+      if (!eval.getCurrentModuleEnvironment().getName().equals(ModuleEnvironment.SHELL_MODULE)) {
+        extendCurrentModule(this.getLocation(), name, eval);
+      }
+      else {
+        eval.warning("importing " + name + ", instead of extending.", URIUtil.rootLocation("prompt"));
+        importModule(name, this.getLocation(), eval);
+      }
+
 			return org.rascalmpl.interpreter.result.ResultFactory.nothing();
 		}
 	}