54 lines
1.1 KiB
Rust
54 lines
1.1 KiB
Rust
// no-reformat
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/*
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*
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* When you write a block-expression thing followed by
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* a lone unary operator, you can get a surprising parse:
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*
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* if (...) { ... }
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* -num;
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*
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* for example, or:
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*
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* if (...) { ... }
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* *box;
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*
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* These will parse as subtraction and multiplication binops.
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* To get them to parse "the way you want" you need to brace
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* the leading unops:
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* if (...) { ... }
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* {-num};
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*
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* or alternatively, semi-separate them:
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*
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* if (...) { ... };
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* -num;
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*
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* This seems a little wonky, but the alternative is to lower
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* precedence of such block-like exprs to the point where
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* you have to parenthesize them to get them to occur in the
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* RHS of a binop. For example, you'd have to write:
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*
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* 12 + (if (foo) { 13 } else { 14 });
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*
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* rather than:
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*
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* 12 + if (foo) { 13 } else { 14 };
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*
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* Since we want to maintain the ability to write the latter,
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* we leave the parens-burden on the trailing unop case.
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*
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*/
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fn main() {
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let num = 12;
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assert if (true) { 12 } else { 12 } - num == 0;
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assert 12 - if (true) { 12 } else { 12 } == 0;
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if (true) { 12 } {-num};
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if (true) { 12 }; {-num};
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if (true) { 12 };;; -num;
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}
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