error[E0308]: mismatched types
  --> $DIR/issue-81293.rs:6:13
   |
LL |     a = c + b * 5;
   |             ^^^^^ expected `usize`, found `u16`

error[E0308]: mismatched types
  --> $DIR/issue-81293.rs:6:9
   |
LL |     let a: u16;
   |            --- expected due to this type
...
LL |     a = c + b * 5;
   |         ^^^^^^^^^ expected `u16`, found `usize`

error[E0277]: cannot add `u16` to `usize`
  --> $DIR/issue-81293.rs:6:11
   |
LL |     a = c + b * 5;
   |           ^ no implementation for `usize + u16`
   |
   = help: the trait `Add<u16>` is not implemented for `usize`
   = help: the following other types implement trait `Add<Rhs>`:
             <&'a f32 as Add<f32>>
             <&'a f64 as Add<f64>>
             <&'a i128 as Add<i128>>
             <&'a i16 as Add<i16>>
             <&'a i32 as Add<i32>>
             <&'a i64 as Add<i64>>
             <&'a i8 as Add<i8>>
             <&'a isize as Add<isize>>
           and 48 others

error: aborting due to 3 previous errors

Some errors have detailed explanations: E0277, E0308.
For more information about an error, try `rustc --explain E0277`.