Unused assignment warning should trigger for structs

This code should ideally trigger warnings about unused assignments, but it doesn't.

struct Pos {
    x: i32
}

fn foo() -> Pos{
    Pos{x: 2}
}

fn main() {
    foo().x += 1; // Unused assignment
    let mut f = Pos { x: 2 };
    f.x = 2; // Unused assignment
}

It could be useful in situations like this:

struct Property {
    x: i32
}

struct Foo {
    prop: Property
}

impl Foo {
    fn prop(&self) -> Property {
        self.prop
    }
    fn mut_prop(&mut self) -> &mut Property {
        &mut self.prop
    }
}

fn main() {
    let mut foo = Foo{prop: Property{x: 2}};
    foo.prop().x += 2; // Oops, accidentally called prop() instead of mut_prop()
    foo.mut_prop().x += 2;
}

1. This code should ideally trigger warnings about unused assignments, but it doesn't.

   struct Pos {
       x: i32
   }
   
   fn foo() -> Pos{
       Pos{x: 2}
   }
   
   fn main() {
       foo().x += 1; // Unused assignment
       let mut f = Pos { x: 2 };
       f.x = 2; // Unused assignment
   }
   

   It could be useful in situations like this:

   struct Property {
       x: i32
   }
   
   struct Foo {
       prop: Property
   }
   
   impl Foo {
       fn prop(&self) -> Property {
           self.prop
       }
       fn mut_prop(&mut self) -> &mut Property {
           &mut self.prop
       }
   }
   
   fn main() {
       let mut foo = Foo{prop: Property{x: 2}};
       foo.prop().x += 2; // Oops, accidentally called prop() instead of mut_prop()
       foo.mut_prop().x += 2;
   }
   

   <!-- TRIAGEBOT_START --> <!-- TRIAGEBOT_ASSIGN_START --> <!-- TRIAGEBOT_ASSIGN_DATA_START$${"user":"LeSeulArtichaut"}$$TRIAGEBOT_ASSIGN_DATA_END --> <!-- TRIAGEBOT_ASSIGN_END --> <!-- TRIAGEBOT_END -->

   rustbot at 2020-04-24 17:49:56

2. Triage: no change.

   Steve Klabnik at 2016-02-02 21:48:50

3. Triage: no change

   Steve Klabnik at 2018-09-24 17:49:58

4. I’ll try to take a look at this! @rustbot claim

   Léo Lanteri Thauvin at 2020-04-24 17:49:55