Binoculars show even when they have no effect on the visualization

[diegorodriguezv]

• [ x ] I have checked the latest main branch to see if this has already been fixed
• [ x ] I have searched existing issues and pull requests for duplicates

URL to the section(s) of the book with this problem:
https://rust-book.cs.brown.edu/ch04-01-what-is-ownership.html

Description of the problem:

The binocular button on some examples do not work. If you click the button it will change color but nothing happens. I assumed the button was a decorative item until I reached this part:

Note: you may wonder how we are executing this Rust program that doesn't compile. We use special tools to simulate Rust...

I followed the link and found that aquascope has the same binoculars button but it works correctly displaying the types of the values.
Then I went back and checked that the button doesn't work on some examples but it works in others, including the examples in the already answered first quiz.

Examples where the binoculars button doesn't work:

I'll write the first line of the paragraph above the example with the error:

• Here's a program like the one you saw in Section 3.3 that ...
• When an expression reads a variable, the variable's value ...
• However, copying data can take up a lot of ...

By looking at the ch04-01-what-is-ownership.md code, I can't really tell what is the problem.

Suggested fix:

The binoculars button should work in these examples the same as in the other examples and the aquascope site or they should be removed.

[willcrichton]

Thanks for the report. The binoculars have no effect for traces that have no expandable data types, like boxes. I'll make a note to hide the button when it's not applicable to a particular trace.

[diegorodriguezv]

Thanks @willcrichton.
I feel partially embarrassed now that I finished the chapter and understand a little more the rust memory paradigm. I also understand now that the button shows the type and contents for a pointer but not variables. But anyway this behavior is something that can appear confusing for a beginner.