Using boolean operations with match expressions yields unexpected compiler errors

[utoalex]

Hi Rust team! First of all, sorry if this has been already reported, but I couldn't find any issue related to this one.

Using a match expression as a bool and combining it with other bools using boolean operators yields compiler errors which appear to be unexpected.

Example code that reproduces the compiler errors:

fn test_match_bool(bool_slice: &[bool], maybe_bool: Option<bool>) -> bool {
    match maybe_bool {
        Some(a_bool) => a_bool,
        None => true
    } && bool_slice[0]
}

fn main() {
    println!("{}", test_match_bool(&[false, true], Some(false)));
}

This yields the following compiler errors:

error[E0308]: mismatched types
 --> src/main.rs:2:5
  |
2 | /     match maybe_bool {
3 | |         Some(a_bool) => a_bool,
4 | |         None => true
5 | |     } && bool_slice[0]
  | |     ^- help: consider using a semicolon here
  | |_____|
  |       expected `()`, found `bool`

error[E0308]: mismatched types
 --> src/main.rs:5:7
  |
1 | fn test_match_bool(bool_slice: &[bool], maybe_bool: Option<bool>) -> bool {
  |                                                                      ---- expected `bool` because of return type
...
5 |     } && bool_slice[0]
  |       ^^^^^^^^^^^^^^^^ expected `bool`, found `&&bool`

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0308`.

It looks like the compiler fails to understand that the expression continues after the match expression, and then reads && bool_slice[0] as being a new expression of type &&bool.

Oddly enough, prepending a return keyword to the whole expression:

fn test_match_bool(bool_slice: &[bool], maybe_bool: Option<bool>) -> bool {
    return match maybe_bool {
        Some(a_bool) => a_bool,
        None => true
    } && bool_slice[0]
}

fn main() {
    println!("{}", test_match_bool(&[false, true], Some(false)));
}

causes the compiler to compile the code successfully.

This happens both on stable and nightly compilers.

[estebank]

Output in nightly after #74650:

error[E0308]: mismatched types
 --> src/main.rs:2:5
  |
2 | /     match maybe_bool {
3 | |         Some(a_bool) => a_bool,
4 | |         None => true
5 | |     } && bool_slice[0]
  | |     ^- help: consider using a semicolon here
  | |_____|
  |       expected `()`, found `bool`

error[E0308]: mismatched types
 --> src/main.rs:5:7
  |
1 | fn test_match_bool(bool_slice: &[bool], maybe_bool: Option<bool>) -> bool {
  |                                                                      ---- expected `bool` because of return type
...
5 |     } && bool_slice[0]
  |       ^^^^^^^^^^^^^^^^ expected `bool`, found `&&bool`
  |
help: parentheses are required to parse this as an expression
  |
2 |     (match maybe_bool {
3 |         Some(a_bool) => a_bool,
4 |         None => true
5 |     }) && bool_slice[0]
  |

[utoalex]

Oh my, my nightly compiler was not up-to-date, sorry.
Closing this issue then.