ucsd-progsys/liquidhaskell

Document that specs can depend on arguments of enclosing functions

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#2,442 建立於 2024年11月19日

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描述

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.

貢獻者指南

技術棧
無
領域
documentation
議題類型
documentation
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
3
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
1-3 hours
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
fresh
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
clear
前置要求
basic Haskellfamiliarity with Liquid Haskell
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
70
研究方向
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.