Error code E0699
Note: this error code is no longer emitted by the compiler.
A method was called on a raw pointer whose inner type wasn't completely known.
Erroneous code example:
#![deny(warnings)] fn main() { let foo = &1; let bar = foo as *const _; if bar.is_null() { // ... } }
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):
#![allow(unused)] fn main() { let foo = &1; let bar = foo as *const i32; if bar.is_null() { // ... } }
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
}
}
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.