Autocompletion hangs in custom MultiHostInjector

I defined the following instance of MultiHostInjector to treat comments a java methods' bodies:

public class MyCustomMultiHostInjector implements MultiHostInjector {

    @Override
    public void getLanguagesToInject(@NotNull MultiHostRegistrar registrar, @NotNull PsiElement context) {
        if (context instanceof PsiDocComment) return;
        final PsiComment psiComment = (PsiComment) context;

        registrar.startInjecting(JavaLanguage.INSTANCE);
        registrar.addPlace(
                "class A { void method() { ",
                "; }}",
                (PsiLanguageInjectionHost) context,
                new TextRange(3, psiComment.getTextLength())
        );
        registrar.doneInjecting();
    }

    @NotNull
    @Override
    public List<? extends Class<? extends PsiElement>> elementsToInjectIn() {
        return Collections.singletonList(PsiComment.class);
    }
}

Intellij IDEA recognizes a comment a body of a java method, it adds highlighting, but when I try to use autocompletion (like // System.<CTRL+SPACE>) it hangs: the progress ring is spinning forever:

What is wrong with my class?