mirror of
https://github.com/rust-lang/rust.git
synced 2024-11-30 02:33:55 +00:00
63 lines
1.4 KiB
Rust
63 lines
1.4 KiB
Rust
// run-pass
|
|
|
|
#![allow(unused_must_use)]
|
|
#![allow(unused_parens)]
|
|
// This test has some extra semis in it that the pretty-printer won't
|
|
// reproduce so we don't want to automatically reformat it
|
|
|
|
// no-reformat
|
|
|
|
|
|
/*
|
|
*
|
|
* When you write a block-expression thing followed by
|
|
* a lone unary operator, you can get a surprising parse:
|
|
*
|
|
* if (...) { ... }
|
|
* -num;
|
|
*
|
|
* for example, or:
|
|
*
|
|
* if (...) { ... }
|
|
* *box;
|
|
*
|
|
* These will parse as subtraction and multiplication binops.
|
|
* To get them to parse "the way you want" you need to brace
|
|
* the leading unops:
|
|
|
|
* if (...) { ... }
|
|
* {-num};
|
|
*
|
|
* or alternatively, semi-separate them:
|
|
*
|
|
* if (...) { ... };
|
|
* -num;
|
|
*
|
|
* This seems a little wonky, but the alternative is to lower
|
|
* precedence of such block-like exprs to the point where
|
|
* you have to parenthesize them to get them to occur in the
|
|
* RHS of a binop. For example, you'd have to write:
|
|
*
|
|
* 12 + (if (foo) { 13 } else { 14 });
|
|
*
|
|
* rather than:
|
|
*
|
|
* 12 + if (foo) { 13 } else { 14 };
|
|
*
|
|
* Since we want to maintain the ability to write the latter,
|
|
* we leave the parens-burden on the trailing unop case.
|
|
*
|
|
*/
|
|
|
|
pub fn main() {
|
|
|
|
let num = 12;
|
|
|
|
assert_eq!(if (true) { 12 } else { 12 } - num, 0);
|
|
assert_eq!(12 - if (true) { 12 } else { 12 }, 0);
|
|
if (true) { 12; } {-num};
|
|
if (true) { 12; }; {-num};
|
|
if (true) { 12; };;; -num;
|
|
//~^ WARNING unnecessary trailing semicolons
|
|
}
|