Paths - The Rust Reference

# Paths

A path is a sequence of one or more path components logically separated by a namespace qualifier (`::`). If a path consists of only one component, it may refer to either an item or a variable in a local control scope. If a path has multiple components, it refers to an item.

Every item has a canonical path within its crate, but the path naming an item is only meaningful within a given crate. There is no global namespace across crates; an item's canonical path merely identifies it within the crate.

Two examples of simple paths consisting of only identifier components:

    x;
    x::y::z;

Path components are usually identifiers, but they may also include angle-bracket-enclosed lists of type arguments. In expression context, the type argument list is given after a `::` namespace qualifier in order to disambiguate it from a relational expression involving the less-than symbol (`<`). In type expression context, the final namespace qualifier is omitted.

Two examples of paths with type arguments:

    # #![allow(unused_variables)]
    #fn main() {
    # struct HashMap<K, V>(K,V);
    # fn f() {
    # fn id<T>(t: T) -> T { t }
    type T = HashMap<i32,String>; // Type arguments used in a type expression
    let x  = id::<i32>(10);       // Type arguments used in a call expression
    # }

    #}

Paths can be denoted with various leading qualifiers to change the meaning of how it is resolved:

- Paths starting with `::` are considered to be global paths where the components of the path start being resolved from the crate root. Each identifier in the path must resolve to an item.

    mod a {
        pub fn foo() {}
    }
    mod b {
        pub fn foo() {
            ::a::foo(); // call a's foo function
        }
    }
    # fn main() {}

- Paths starting with the keyword `super` begin resolution relative to the parent module. Each further identifier must resolve to an item.

    mod a {
        pub fn foo() {}
    }
    mod b {
        pub fn foo() {
            super::a::foo(); // call a's foo function
        }
    }
    # fn main() {}

- Paths starting with the keyword `self` begin resolution relative to the current module. Each further identifier must resolve to an item.

    fn foo() {}
    fn bar() {
        self::foo();
    }
    # fn main() {}

Additionally keyword `super` may be repeated several times after the first `super` or `self` to refer to ancestor modules.

    mod a {
        fn foo() {}

        mod b {
            mod c {
                fn foo() {
                    super::super::foo(); // call a's foo function
                    self::super::super::foo(); // call a's foo function
                }
            }
        }
    }
    # fn main() {}