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[SR-14939] Compiler error for assumed throw that does not happen #57281

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swift-ci opened this issue Jul 18, 2021 · 1 comment
Open

[SR-14939] Compiler error for assumed throw that does not happen #57281

swift-ci opened this issue Jul 18, 2021 · 1 comment
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself

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@swift-ci
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Previous ID SR-14939
Radar rdar://problem/80820406
Original Reporter fredap (JIRA User)
Type Bug
Environment

Xcode Version 12.5.1 (12E507) on the Mac

Note that this problem also happens on the Linux platform (Docker image version 5.3)

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug
Assignee None
Priority Medium

md5: 44803371d9ed3e7ba09dd4f36547b315

Issue Description:

I have the following code:

import Foundation
import XCTest

struct SomeError: Error { }

func throwingFunction() throws {
    throw SomeError()
}

class TestCase: XCTestCase {

    func testMethod() {
        DispatchQueue.global().async {
            do {
                XCTAssertThrowsError(try throwingFunction())
            } catch {
                // ignore
            }
        }
    }
}

This code produces a warning:

'catch' block is unreachable because no errors are thrown in 'do' block

which seems to indicate that the do block does not throw an error (which is also the expectation). The obvious solution is to remove the catch block:

class TestCase: XCTestCase {

    func testMethod() {
        DispatchQueue.global().async {
            XCTAssertThrowsError(try throwingFunction())
        }
    }
}

which then produces the error:

Invalid conversion from throwing function of type '() throws -> Void' to non-throwing function type '@convention(block) () -> Void'

which seems to indicate that XCTAssertThrowsError does throw an error
@typesanitizer
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Minimal example:

func f(_: @escaping () -> ()) {}
func g(_: @escaping @autoclosure () throws -> ()) {}
func k() throws {}

let _ = f { // invalid conversion from throwing function of type '() throws -> ()' to non-throwing function type '() -> ()'
    g(try k())
}

The problem is that @autoclosure is not handled correctly.

@swift-ci create

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself
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@typesanitizer @swift-ci