swiftlang/swift

Bad diagnostic for `any P!`

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#72,662 opened on Mar 28, 2024

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 (6 comments) (0 reactions) (2 assignees)Swift (69,989 stars) (10,719 forks)batch import
TypeResolverbugcompilerdiagnostics qualityexistentialsgood first issueimplicitly unwrapped optionalsswift 6.0type checkertypesunexpected behavior

Description

Description

No response

Reproduction

protocol P {}

// error: using '!' is not allowed here; perhaps '?' was intended? [implicitly_unwrapped_optional_in_illegal_position]
// error: optional 'any' type must be written '(any P2)?' [incorrect_optional_any]
let _: any P!

Expected behavior

A single error, optional 'any' type must be written '(any P)!', as in the case of let _: any P?.

Environment

Swift version 6.0-dev (LLVM 48dc0c6fa01ce9e, Swift 19fbe5b33d423d1) Target: x86_64-apple-macosx14.0

Additional information

This https://github.com/apple/swift/labels/good%20first%20issue will suit an experienced Swift user.

Contributor guide

Tech stack
swift
Domain
tooling
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.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Swift compiler basicsDiagnostic system
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
This bug report describes an incorrect diagnostic for `any P!` in Swift. The compiler currently emits two errors instead of one when encountering an implicitly unwrapped optional in an illegal position with `any`. The fix likely involves modifying the error checking logic in the parser or type checker to suppress the spurious first error. The issue has two assignees but no open PRs, indicating someone may be working on it. Comments on the issue may provide additional context.