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Treat await as an almost-unary operator. #711
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Making pipe behave like application seems pretty unlikely. First `->` has deep binary operator behavior, including associating to the left on a->b->c, and mixes in specific ways with other operators. Instead application lives on a different level entirely with no issues of how to treat specially the right-hand-side which is enclosed in parens. The await operator is essentially a unary operator. After all it takes on argument. It is also treated as such in JS. Some expected behaviours are that `await 2 + await 3` just like `-2 + -3` is expected to mean `(await 2) + (await 3)`. The issue raised is with pipe: the desired outcome is that `await a->b` is parsed as `await a->b`. However notice that `- a->b` is parsed as `(-a)->b`. So on one side, one would like to have `await` behave like other unary operators. On the other side one wouldn't. As a compromise, this PR treats `await` as an almost-unary operator. In the sense that it binds more tightly than any "real" binary operator such as `+` and `**`, but not more than `->` and `.`. This introduces some lack of uniformity, and requires special-casing parts of parsing and printing.
cristianoc
changed the title
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@cknitt this should be ready to go. Take a look: it should address the last comment on printing. |
mununki
approved these changes
Oct 31, 2022
| @@ -175,7 +175,11 @@ let flattenOperandRhs parentOperator rhs = | |||
| | _ when ParsetreeViewer.isTernaryExpr rhs -> true | |||
| | _ -> false | |||
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| let lazyOrAssertOrAwaitExprRhs expr = | |||
| let binaryOperatorInsideAwaitNeedsParens operator = | |||
| ParsetreeViewer.operatorPrecedence operator | |||
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Is there a behind history? it seems different from Res_token.precedence.
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Making pipe behave just like application seems pretty unlikely. First
->has deep binary operator behavior, including associating to the left ona->b->c, and mixes in specific ways with other operators. Instead application lives on a different level entirely with no issues of how to treat specially the right-hand-side which is enclosed in parens (and lives in a radically different place in the call stack of the parser).The await operator is essentially a unary operator. After all it takes one argument. It is also treated as such in JS. Some expected behaviours are that
await 2 + await 3just like-2 + -3is expected to mean(await 2) + (await 3). Or:await getName() ++ await getSurname().The issue raised by people who have tried
awaitis in combination with pipe: the desired outcome is thatawait a->bis parsed asawait (a->b). However notice that- a->bis parsed as(-a)->b, so that's a difference.So on one side, one would like to have
awaitbehave like other unary operators. On the other side one wouldn't.As a compromise, this PR treats
awaitas an almost-unary operator. In the sense that it binds more tightly than any "real" binary operator such as+and**, but not->and..This introduces some lack of uniformity, and requires special-casing parts of parsing and printing.