Change operator precedence #4075
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proposals/p4075.md
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| - It is used in an `impl` declaration to specify the values of associated | ||
| constants (such as associated types). In that context, `impl T as I where R` | ||
| is interpreted conceptually as `impl T as (I where R)`. It would be nice if | ||
| `T as I where R` would mean the same thing in other contexts. |
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Maybe worth noting here: if we don't get the "would be nice" version, we want it to be invalid rather than meaning (T as I) where R. That is, considered in isolation, we would prefer T as (I where R) > invalid > (T as I) where R.
proposals/p4075.md
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| `T as I where R` would mean the same thing in other contexts. | ||
| - The `where` operator will frequently be used with the binary `&` operator, | ||
| since that is how facet types are combined. It is desirable that | ||
| `I & J where R` be interpreted as `(I & J) where R`. This is expected to be |
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Likewise here: considered in isolation, we probably prefer (I & J) where R > invalid > I & (I where R).
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Just wanted to say I'm generally happy with this. Leaving the detail review to @zygoloid. I'm also not concerned if we discover we want to make a further tweak here based on experience, this still seems like a good improvement and bringing the where clause into the picture.
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Note to self: include link to open discussion on 06-13 https://docs.google.com/document/d/1s3mMCupmuSpWOFJGnvjoElcBIe2aoaysTIdyczvKX84/edit?resourcekey=0-G095Wc3sR6pW1hLJbGgE0g&tab=t.0#heading=h.p46elxrmhh8x
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Done. |
Update the operator precedence to achieve a few goals:
if...then...else, behave similarly to the left, so that rearranging expressions won't change how they group.whereoperator, used to specify constraints on facet types, to the precedence chart, to define how it interacts with other operators.