swiftlang/swift

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

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#44,166 opened on May 18, 2016

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Description
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.

Contributor guide

Research direction
Modify the compiler to emit a warning instead of an error for unused function typed return values. Look at how other unused results are handled.
Tech stack
swift
Domain
compilers
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
1
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Swift
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80