java completion: don't always cast qualifier when return type is narrowed (IDEA-186652, IDEA-186609)

only when that narrowed type is expected

java/java-tests/testData/codeInsight/completion/normal/NarrowingReturnTypeInVoidContext.java

@@ -0,0 +1,18 @@
+interface TypeA { }
+interface TypeB extends TypeA { }
+
+interface ProviderOfA {
+    TypeA getObject();
+}
+
+interface ProviderOfB extends ProviderOfA {
+    TypeB getObject();
+}
+
+class IntelliJPostCastScopeBug {
+    void foo(ProviderOfA provider) {
+        if (provider instanceof ProviderOfB) {
+            provider.getObje<caret>
+        }
+    }
+}

java/java-tests/testData/codeInsight/completion/normal/NarrowingReturnTypeInVoidContext_after.java

@@ -0,0 +1,18 @@
+interface TypeA { }
+interface TypeB extends TypeA { }
+
+interface ProviderOfA {
+    TypeA getObject();
+}
+
+interface ProviderOfB extends ProviderOfA {
+    TypeB getObject();
+}
+
+class IntelliJPostCastScopeBug {
+    void foo(ProviderOfA provider) {
+        if (provider instanceof ProviderOfB) {
+            provider.getObject()<caret>
+        }
+    }
+}