swiftlang/swift

[SR-12583] `foo() {} {}` parses but `foo {} {}` does not

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#55,028 opened on Apr 14, 2020

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Description
Previous ID SR-12583
Radar rdar://problem/62202372
Original Reporter @jckarter
Type Bug
Votes 1
Component/s Compiler
Labels Bug, StarterBug
Assignee None
Priority Medium

md5: f3208365889a29361424efaa2b6814cd

Issue Description:

If you have a function that takes a function, then returns a function that takes another function:

func foo(_: ()->()) -> (() -> ()) -> () { fatalError() }

Then you can call it like this:

foo() {} {}

but this doesn't parse:

foo {} {}

Contributor guide

Research direction
Investigate the Swift parser's handling of trailing closures when the function call omits parentheses. Compare the parsing paths for `foo() {} {}` and `foo {} {}` to identify where the latter fails.
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.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
Swift
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60