swiftlang/swift

[SR-1557] Unused function-typed return values result in a hard error

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#44,166 建立於 2016年5月18日

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 (5 留言) (0 反應) (0 負責人)Swift (69,989 star) (10,719 fork)batch import
bugcompilergood first issue

描述
Previous ID SR-1557
Radar None
Original Reporter H2CO3 (JIRA User)
Type Bug

OS X 10.10.5, swiftc version 2.1 (swiftlang-700.1.101.6 clang-700.1.76)
Votes 0
Component/s Compiler
Labels Bug, StarterBug
Assignee None
Priority Medium

md5: f02d43f7c7b9cce2527f9568acf6ac13

Issue Description:

If a function returns a function, and the return value of the former is unused, a compilation error occurs:

    public func foo(x: Int) -> () -> Int {
        return { x }
    }

    foo(42) // ignored return value errors out: "expression resolves to an unused function"

For consistency (and convenience of testing, where I found this problem), such unused return values should yield a warning only.

貢獻者指南

技術棧
swift
領域
tooling
議題類型
bug
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。
1-2 days
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。
stale
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
Swift syntaxbasic compiler concepts
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 unused function typed return values produce a hard error instead of a warning. The fix likely involves modifying the compiler's diagnostic for unused results in the type checker or semantic analysis (Sema). Relevant files may include lib/Sema/TypeCheck... or lib/AST/Diagnostics... Examine the existing warning for unused non function return values and extend it to function types. The issue is labeled StarterBug and has 5 comments, some possibly providing guidance.