swiftlang/swift

[SR-1807] Sema should catch and warn about self capture in closures

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#44,416 opened on Jun 17, 2016

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Description
Previous ID SR-1807
Radar rdar://26865978
Original Reporter @CodaFi
Type New Feature
Votes 0
Component/s Compiler
Labels New Feature, StarterBug
Assignee None
Priority Medium

md5: 3ea294e377274fa3d27e3c3b76ff7bbd

Issue Description:

To maintain parity with Objective-C, we should use our ARC analysis pass in Sema to check for the presence of self capture in blocks without weak or @noescape. This should be a very simple warning modeled after the one in /clang/lib/Sema/SemaChecking.cpp void diagnoseRetainCycle().

Contributor guide

Tech stack
swiftcpp
Domain
tooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
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.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C++compiler internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
The issue requests adding a warning in the Swift compiler's semantic analysis (Sema) to detect self capture in closures without weak or @noescape. The implementation should follow the existing diagnoseRetainCycle() function in clang/lib/Sema/SemaChecking.cpp. Look into the Swift compiler's ARC analysis pass and add a similar check. The warning should be emitted when a closure captures self strongly and the closure escapes.