"Filter predicates should not be aliased." seems too strict

[samuelcolvin]

Describe the bug

Aliases are not allowed as filter predicates.

As per datafusion-contrib/datafusion-functions-json#26 (comment) @alamb suggested we work around change of alias when substituting functions to replace operators by using Expr::Alias.

However when substituting foo ? 'bar' with a function wrapped in an alias, we get an error

Plan("Attempted to create Filter predicate with expression `json_contains(test.json_data, Utf8(\"foo\"))` aliased as 'json_data ? Utf8(\"foo\")'. Filter predicates should not be aliased.")

This is caused by

datafusion/datafusion/expr/src/logical_plan/plan.rs

Lines 2133 to 2140 in 08c5345

	// filter predicates should not be aliased
	if let Expr::Alias(Alias { expr, name, .. }) = predicate {
	return plan_err!(
	"Attempted to create Filter predicate with \
	expression `{expr}` aliased as '{name}'. Filter predicates should not be \
	aliased."
	);
	}

Ref #3796 & #3795

This seems unnecessarily strict.

The problem is that I when replacing the operator, you don't know what part of the query the operator is used in, so you can't decide whether or not to apply the alias AFAIK.

To Reproduce

Add the following test to datafusion-contrib/datafusion-functions-json#26

#[tokio::test]
async fn test_question_filter() {
    let batches = run_query("select name from test where json_data ? 'foo'")
        .await
        .unwrap();

    let expected = [
        "+------------+",
        "| name       |",
        "+------------+",
        "| object_foo |",
        "+------------+",
    ];
    assert_batches_eq!(expected, &batches);
}

Expected behavior

I think aliases as predicates should be allowed.

Additional context

No response