Warn when expression contains = but not ;

[pzmarzly]

In: let mut x  = 5;

In: x = 3
Out: ()


In: x
Out: 5


In: x = 3;

In: x
Out: 3

This behavior may be surprising sometimes. I'm not sure what the right way to improve it is, but my suggestion is printing a warning between In: and Out: about it whenever someone writes a line with = but not ;

[sigmaSd]

I like the idea!, I implemented it but there are cases when you get an ugly messages like

Are you missing an `;` ?
   Compiling irust v0.1.0 (/tmp/irust)
warning: variable `x` is assigned to, but never used
 --> src/main.rs:2:6
  |
2 |     let x = 5;
  |         ^
  |
  = note: #[warn(unused_variables)] on by default
  = note: consider using `_x` instead

warning: value assigned to `x` is never read
 --> src/main.rs:4:1
  |
4 | x = 6
  | ^
  |
  = note: #[warn(unused_assignments)] on by default
  = help: maybe it is overwritten before being read?

error[E0384]: cannot assign twice to immutable variable `x`
 --> src/main.rs:4:1
  |
2 |     let x = 5;
  |         -
  |         |
  |         first assignment to `x`
  |         help: make this binding mutable: `mut x`
3 |     println!("{:?}", {
4 | x = 6
  | ^^^^^ cannot assign twice to immutable variable

error: aborting due to previous error

For more information about this error, try `rustc --explain E0384`.
error: Could not compile `irust`.

To learn more, run the command again with --verbose.

I think there are steps we need to do before doing this,

1- format output, At first I liked the separation of concerns by making parse() returns a string that is printed by handle_enter(), but now I feel its really limiting, since I'm printing all kind of output the same way, instead of being able to customize per function, for example print "Are you missing an ; ?" with different color, plus I already break that encapsulation with art.rs wait_for_cmd

2- format rustc errors, I want this:

   Compiling irust v0.1.0 (/tmp/irust)
warning: variable `x` is assigned to, but never used
 --> src/main.rs:2:6
  |
2 |     let x = 5;
  |         ^
  |
  = note: #[warn(unused_variables)] on by default
  = note: consider using `_x` instead

to become

 --> src/main.rs:2:6
  |
2 |     let x = 5;
  |         ^
  |

[sigmaSd]

• format rustc errors ba06cf7

[sigmaSd]

@pzmarzly here is a PR for this issue, #9, would be great if you check it out

[sigmaSd]

should be good now c288e4f