EA-39175 Completion fails if MultiDeclaration is present on top level in file

compiler/frontend/src/org/jetbrains/jet/lang/resolve/lazy/AbstractLazyMemberScope.java

@@ -245,8 +245,9 @@ public abstract class AbstractLazyMemberScope<D extends DeclarationDescriptor, D
                         getProperties(name);
                     }
                 }
-                else if (declaration instanceof JetTypedef) {
+                else if (declaration instanceof JetTypedef || declaration instanceof JetMultiDeclaration) {
-                    // Do nothing as typedefs are not supported
+                    // Do nothing for typedefs as they are not supported.
+                    // MultiDeclarations are not supported on global level too.
                 }
                 else {
                     throw new IllegalArgumentException("Unsupported declaration kind: " + declaration);

compiler/frontend/src/org/jetbrains/jet/lang/resolve/lazy/AbstractPsiBasedDeclarationProvider.java

@@ -64,7 +64,7 @@ public abstract class AbstractPsiBasedDeclarationProvider implements Declaration
             JetClassOrObject classOrObject = (JetClassOrObject) declaration;
             classesAndObjects.put(classOrObject.getNameAsName(), classOrObject);
         }
-        else if (declaration instanceof JetParameter || declaration instanceof JetTypedef) {
+        else if (declaration instanceof JetParameter || declaration instanceof JetTypedef || declaration instanceof JetMultiDeclaration) {
             // Do nothing, just put it into allDeclarations is enough
         }
         else {

idea/testData/completion/basic/InFileWithMultiDeclaration.kt

@@ -0,0 +1,12 @@
+data class LocalData(val first : Int, val second : Int)
+
+val (localFirst, localSecond) = LocalData(11, 12)
+
+fun test() {
+  local<caret>
+}
+
+// Test that this test won't fail with exception
+// Regression for EA-39175
+
+// ABSENT: localFirst, localSecond

idea/tests/org/jetbrains/jet/completion/JetBasicCompletionTest.java

@@ -100,6 +100,10 @@ public class JetBasicCompletionTest extends JetCompletionTestBase {
         doTest();
     }
 
+    public void testInFileWithMultiDeclaration() {
+        doTest();
+    }
+
     public void testInFileWithTypedef() {
         doTest();
     }