Suspicious check in Resolver.findClassInPackage

[michaelhixson]

Document or fix this suspicious-looking element kind check in Resolver.findClassInPackage.

checker-framework/javacutil/src/main/java/org/checkerframework/javacutil/Resolver.java

Lines 278 to 289 in cff1a03

	Element res =
	wrapInvocationOnResolveInstance(
	FIND_IDENT_IN_PACKAGE,
	env,
	pck,
	names.fromString(name),
	Kinds.KindSelector.TYP);
	if (res.getKind() == ElementKind.CLASS) {
	return (ClassSymbol) res;
	} else {
	return null;
	}

Why does it check for exactly ElementKind.CLASS? Why doesn't it do something like this instead?

if (res.getKind().isClass() || res.getKind().isInterface()) {
    return (ClassSymbol) res;
} else {
    return null;
}

Its only caller is in FlowExpressionParseUtil.

checker-framework/framework/src/main/java/org/checkerframework/framework/util/FlowExpressionParseUtil.java

Lines 494 to 498 in cff1a03

	ClassSymbol classSymbol =
	resolver.findClassInPackage(expr.getNameAsString(), packageSymbol, path);
	if (classSymbol != null) {
	return new ClassName(classSymbol.asType());
	}

It's not clear why that code would not want to find the class if the class was an enum, for example. If there's a reason for this, then perhaps an inline comment should be added to state that reason.

I'm filing this issue because @wmdietl asked me to in #3017.