An assignment operator was used on a non-place expression.
Erroneous code examples:
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:
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 !
}