presto-main/src/main/java/io/prestosql/metadata/FunctionRegistry.java/FunctionRegistry/possibleExactCastMatch
class FunctionRegistry:    private static boolean possibleExactCastMatch(Signature signature, Signature declaredSignature)
    {
        if (!declaredSignature.getTypeVariableConstraints().isEmpty()) {
            return false;
        }
        if (!declaredSignature.getReturnType().getBase().equalsIgnoreCase(signature.getReturnType().getBase())) {
            return false;
        }
        if (!declaredSignature.getArgumentTypes().get(0).getBase().equalsIgnoreCase(signature.getArgumentTypes().get(0).getBase())) {
            return false;
        }
        return true;
    }