E0070 - Error codes index
Description: Book listing all Rust error codes

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# Error code E0070

An assignment operator was used on a non-place expression.

Erroneous code examples:

    #![allow(unused)]
    fn main() {
    struct SomeStruct {
        x: i32,
        y: i32,
    }

    const SOME_CONST: i32 = 12;

    fn some_other_func() {}

    fn some_function() {
        SOME_CONST = 14; // error: a constant value cannot be changed!
        1 = 3; // error: 1 isn't a valid place!
        some_other_func() = 4; // error: we cannot assign value to a function!
        SomeStruct::x = 12; // error: SomeStruct a structure name but it is used
                            //        like a variable!
    }
    }

The left-hand side of an assignment operator must be a place expression. A place expression represents a memory location and can be a variable (with optional namespacing), a dereference, an indexing expression or a field reference.

More details can be found in the Expressions section of the Reference.

And now let’s give working examples:

    #![allow(unused)]
    fn main() {
    struct SomeStruct {
        x: i32,
        y: i32,
    }
    let mut s = SomeStruct { x: 0, y: 0 };

    s.x = 3; // that's good !

    // ...

    fn some_func(x: &mut i32) {
        *x = 12; // that's good !
    }
    }