swiftlang/swift

Error says `@preconcurrency` only applies in inheritance clauses

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#88,338 创建于 2026年4月7日

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@preconcurrencyTypeResolverattributescompilergood first issueswift 6.3type checker

描述

Description

This is not true. The attribute can also be used on declarations such as types, functions, and imports.

Reproduction

let _: @preconcurrency @MainActor() -> Void = {}

error: '@preconcurrency' only applies in inheritance clauses
  83 | 
  84 | let _: @preconcurrency @MainActor() -> Void = {}
     |        `- error: '@preconcurrency' only applies in inheritance clauses
  85 |

Expected behavior

An accurate error message. It might be better to say that @preconcurrency cannot be used on a type attribute instead of enumerating all the valid positions.

Environment

Swift version 6.3-dev (fefcb257b5b5d32)

Additional information

No response

贡献者指南

技术栈
swift
领域
developer experience
议题类型
bug
难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。
2
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1-3 hours
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fresh
清晰度议题是否清楚说明期望改动、验收标准和下一步。
clear
前置要求
无
新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。
70
研究方向
Search the Swift compiler source code for the exact error message 'only applies in inheritance clauses' to locate the diagnostic. The message is likely in a diagnostics file (e.g., DiagnosticsFrontend.def). Once found, modify the string to state that @preconcurrency cannot be used on a type attribute, as suggested in the issue. Ensure the fix is consistent with other diagnostic messages. Then update any existing test cases that reference the old error message to expect the new one.