swiftlang/swift

No fix-it for escaping closure captures 'inout' parameter

Open

#87830 opened on Mar 12, 2026

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 (3 comments) (0 reactions) (1 assignee)Swift (69,989 stars) (10,719 forks)batch import
SILcapture listsclosurescompilerdiagnostics qualityexpressionsfix-itsgood first issueinoutswift 6.3value capturing

Description

Description

No response

Reproduction

func bar(_: @escaping () -> Void) {}
func foo(_ i: inout Int) {
  bar {
    _ = i
  }
}

Expected behavior

An additional note asking if the user wants to capture a copy, with a fix-it to capture the parameter explicitly.

Environment

Swift version 6.3-dev (fefcb257b5b5d32)

Additional information

No response

Contributor guide

Tech stack
swift
Domain
developer experiencetooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
5
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Swift language knowledgeCompiler development basicsUnderstanding of diagnostic system
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
15
Research direction
Investigate the Swift compiler's diagnostic emission for inout captures in escaping closures. The fix it likely needs to be added in the Sema or TypeCheck pass. Look at existing fix its in the codebase, such as those in lib/Sema/TypeCheckClosures.cpp or lib/AST/DiagnosticSema. Check if the assignee has a branch or comments indicating progress. The expected behavior is to suggest capturing the parameter explicitly (e.g., `let copy = i`). Refer to similar fix its for reference.