# Error code E0699

A method was called on a raw pointer whose inner type wasn’t completely known.

Erroneous code example:

ⓘ

    let foo = &1;
    let bar = foo as *const _;
    if bar.is_null() {
        // ...
    }

Run

Here, the type of `bar` isn’t known; it could be a pointer to anything. Instead, specify a type for the pointer (preferably something that makes sense for the thing you’re pointing to):

    let foo = &1;
    let bar = foo as *const i32;
    if bar.is_null() {
        // ...
    }

Run

Even though `is_null()` exists as a method on any raw pointer, Rust shows this error because Rust allows for `self` to have arbitrary types (behind the arbitrary_self_types feature flag).

This means that someone can specify such a function:

ⓘ

    impl Foo {
        fn is_null(self: *const Self) -> bool {
            // do something else
        }
    }

Run

and now when you call `.is_null()` on a raw pointer to `Foo`, there’s ambiguity.

Given that we don’t know what type the pointer is, and there’s potential ambiguity for some types, we disallow calling methods on raw pointers when the type is unknown.

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