Chain an "if let" with a boolean expression

Question

I am trying to chain an if let condition with a regular boolean condition.

if let Some(char_first_index) = char_info.first_index_in_string && !char_info.repeats_in_string

However, when I try to run this I get a compiler issue redirecting me to https://github.com/rust-lang/rust/issues/53667. This rfc mainly deals with chaining if let's. Although there is an issue mentioned here https://github.com/rust-lang/rfcs/blob/master/text/2497-if-let-chains.md#dealing-with-ambiguity which mentions dealing with ambiguity in the case of chaining if lets and booleans.

if let PAT = EXPR && EXPR { .. }
// It can either be parsed as (1):

if let PAT = (EXPR && EXPR) { .. }
// or instead as (2):

if (let PAT = EXPR) && EXPR { .. }

Re-ordering to avoid this ambiguity:

if !char_info.repeats_in_string && let Some(char_first_index) = char_info.first_index_in_string

or adding brackets:

if !char_info.repeats_in_string && (let Some(char_first_index) = char_info.first_index_in_string) 

Does not solve the issue and I still get the same compiler error. I'm not sure if the mentioned rfc has been pulled (apologies I'm not all that experienced with github). However, at the moment the only solutions I can find are either to use two separate if conditions:

if !char_info.repeats_in_string {
    if let Some(char_first_index) = char_info.first_index_in_string {

or to use a match block

match (char_info.repeats_in_string, char_info.first_index_in_string) {
    (false, Some(char_first_index)) => { 
        // former contents of if block
    },
    _ => {}
}

is there a way or make the if block work that I am missing or a more elegant solution than the multiple ifs / one-arm match block? Thanks,

Answer 1

You can turn your match version into an if-let expression:

if let (false, Some(char_first_index)) =
    (char_info.repeats_in_string, char_info.first_index_in_string)
{
    // former contents of if block
}

In fact, Clippy will suggest this exact transformation when given the match:

warning: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
  --> src\lib.rs:7:5
   |
7  | /     match (char_info.repeats_in_string, char_info.first_index_in_string) {
8  | |         (false, Some(char_first_index)) => {
9  | |             // former contents of if block
10 | |         }
11 | |         _ => {}
12 | |     }
   | |_____^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#single_match
   = note: `#[warn(clippy::single_match)]` on by default
help: try
   |
7  ~     if let (false, Some(char_first_index)) = (char_info.repeats_in_string, char_info.first_index_in_string) {
8  +         // former contents of if block
9  +     }
   |