Two consecutive if lets cannot be used as function result

[hellow554]

MCVE

fn nowork(a: Option<u32>, b: Option<u32>) -> bool {
    if let Some(x) = a { true } else { false }
    &&
    if let Some(y) = a { true } else { false }
}

fn work(a: Option<u32>, b: Option<u32>) -> bool {
    let z = if let Some(x) = a { true } else { false }
    &&
    if let Some(y) = a { true } else { false };
    z
}

Error:

error[E0308]: mismatched types
 --> src/main.rs:2:26
  |
2 |     if let Some(x) = a { true } else { false }
  |                          ^^^^ expected (), found bool
  |
  = note: expected type `()`
             found type `bool`

error[E0308]: mismatched types
 --> src/main.rs:2:40
  |
2 |     if let Some(x) = a { true } else { false }
  |                                        ^^^^^ expected (), found bool
  |
  = note: expected type `()`
             found type `bool`

error[E0308]: mismatched types
 --> src/main.rs:3:5
  |
1 |   fn nowork(a: Option<u32>, b: Option<u32>) -> bool {
  |                                                ---- expected `bool` because of return type
2 |       if let Some(x) = a { true } else { false }
3 | /     &&
4 | |     if let Some(y) = a { true } else { false }
  | |______________________________________________^ expected bool, found &&bool
  |
  = note: expected type `bool`
             found type `&&bool`

Am I missing something? Why is the first one not allowed, but the second one?

[Havvy]

The key thing to note here is ^ expected bool, found &&bool. It's not anding your if-lets together, but instead ending the statement at the close of the else. You can fix this by using parenthesis:

https://play.rust-lang.org/?gist=419f4506d17902132dfbe048d88712f4&version=stable&mode=debug&edition=2015

https://doc.rust-lang.org/reference/statements.html#expression-statements for the reason.

[hellow554]

Interesting. Thanks for the two links. So it is intended and also wanted, but not gonna be "fixed"?

[Havvy]

We can add a diagnostic for when its followed by a bin-op like that, but we're not changing the language to accept the code.

[estebank]

Reopening because I'm reverting the change that fixed it because of #74233.