ucsd-progsys/liquidhaskell

Document that specs can depend on arguments of enclosing functions

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#2,442 opened on 2024年11月19日

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説明

Today I learned that the meaning of specs of local bindings can depend on arguments of an enclosing function. For instance, in the following function from the test suite, arg0 is available to the spec of bar.

{-@ foo :: x:_ -> y:_ -> {v:Int | v = x + y} @-}
foo :: Int -> Int -> Int
foo arg0 = bar
  where
    {-@ bar :: x:_ -> {v:Int | v = x + arg0} @-}
    bar arg1 = arg0 + arg1

It doesn't work for other things than arguments though, e.g. z is not in scope in the following spec.

{-@ foo :: x:_ -> y:_ -> {v:Int | v = x + y} @-}
foo :: Int -> Int -> Int
foo arg0 = bar
  where
    z = arg0
    {-@ bar :: x:_ -> {v:Int | v = x + z} @-}
    bar arg1 = arg0 + arg1

We should document the fact that arguments of enclosing functions are in scope. This is also true for other local bindings. See the comments below.

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技術スタック
なし
領域
documentation
Issue 種別
documentation
難度新しい貢献者にとっての実装難度です。1 は非常に小さな変更、5 は専門的な作業です。
3
推定時間経験ある貢献者が調査、実装、テスト、pull request 準備にかけるおおよその時間範囲です。
1-3 hours
活動状況Issue が今どれだけ取り組みやすいかを示します。新しい、活発、古い、ブロック中、またはメンテナー入力待ちなどです。
fresh
明確さ期待される変更、受け入れ条件、次の手順がどれだけ明確かを示します。
clear
前提条件
basic Haskellfamiliarity with Liquid Haskell
初心者向け度初回貢献者にどれだけ取り組みやすいかを 1-100 で推定したスコアです。
70
調査方針
The issue describes that arguments of enclosing functions are in scope for local bindings' specs, but other local bindings are not. To document this, examine the test suite (e.g., the example in the issue) and the comments below the issue for additional cases. The documentation should clarify which variables are available in the scope of a local spec, and mention that it does not work for non argument local bindings. Update the Liquid Haskell documentation accordingly, possibly in the section about refinement types or specifications.