  It looks like you are trying to parse a float literal, but the value you are trying to parse is not a valid float literal.

In Rust, a float literal is a number that is followed by a decimal point and one or more digits. For example, `10.0` is a valid float literal, but `10.` is not.

To fix this error, you can add a digit after the decimal point. For example:
```
let x = 10.0;
```
Alternatively, you can use the `parse` function to convert a string to a float. For example:
```
let x = "10.0".parse::<f64>().unwrap();
```
This will parse the string `"10.0"` as a float and store the result in the variable `x`.