#expect does not show output for try expression

[Kyle-Ye]

Description

Motivation

The original logic is a 3 step computation.

However I'd like to test multi instance and name the instance with number make me sad. So I compress the steps into one throwing function.

But then the #expect macro won't show the output for the left expression with try.

let instance1 = step1(1)
let instance1Data = try step2(instance1)
let instance1String = step3(instance1Data)
#expect(instance1String == "1")

let instance2 = step1(2)
let instance2Data = try step2(instance2)
let instance2String = step3(instance2Data)
#expect(instance2String == "2")

...

⬇️

func helper(_ input: Int) throws -> String {
  let instance = step1(input)
  let data = try step2(instance)
  return step3(data)
}

#expect(try helper(1) == "1")
#expect(try helper(2) == "2")
...

Reproduce

A simplified version to demonstrate the issue

enum MultiError: Error {
    case invalidInput
}

func multi(_ a: Int, _ b: Int) throws -> Int {
    guard a > 0, b > 0 else {
        throw MultiError.invalidInput
    }
    return a * b
}

func multiWithoutThrow(_ a: Int, _ b: Int) -> Int {
    return a * b
}

@Test func example() async throws {
    #expect(try multi(1, 2) == 3)
    #expect(multiWithoutThrow(1, 2) == 3)
}

Expected behavior

Expectation failed: (try multi(1, 2) → 2) == 3
Expectation failed: (multiWithoutThrow(1, 2) → 2) == 3

Actual behavior

Expectation failed: try multi(1, 2) == 3
Expectation failed: (multiWithoutThrow(1, 2) → 2) == 3

Steps to reproduce

See code snippet above

swift-testing version/commit hash

Xcode 16.0

Swift & OS version (output of swift --version ; uname -a)

No response

[Kyle-Ye]

Debugging into swift-testing source code.

They both go into "Expectation failed: \(expectation.evaluatedExpression.expandedDescription())"

But their evaluatedExpression is different.

▿ Testing.__Expression.Kind.generic("try multi(1, 2) == 3")
  ▿ kind : Kind
    - generic : "try multi(1, 2) == 3"
  - runtimeValue : nil

▿ Testing.__Expression.Kind.binaryOperation(lhs: Testing.__Expression.Kind.generic("multi2(1, 2)"), operator: "==", rhs: Testing.__Expression.Kind.generic("3"))
  ▿ kind : Kind
    ▿ binaryOperation : 3 elements
      ▿ lhs : Testing.__Expression.Kind.generic("multi2(1, 2)")
        ▿ kind : Kind
          - generic : "multi2(1, 2)"
        ▿ runtimeValue : Optional<Value>
          ▿ some : 2
            - description : "2"
            - debugDescription : "2"
            ▿ typeInfo : Swift.Int
              ▿ _kind : _Kind
                - type : 0 elements
            - label : nil
            - isCollection : false
            - children : nil
      - operator : "=="
      ▿ rhs : Testing.__Expression.Kind.generic("3")
        ▿ kind : Kind
          - generic : "3"
        ▿ runtimeValue : Optional<Value>
          ▿ some : 3
            - description : "3"
            - debugDescription : "3"
            ▿ typeInfo : Swift.Int
              ▿ _kind : _Kind
                - type : 0 elements
            - label : nil
            - isCollection : false
            - children : nil
  - runtimeValue : nil

[Kyle-Ye]

A temporary workaround is change it from #expect(try multi(1, 2) == 3) to #expect((try multi(1, 2)) == 3)

Then we'll get the expected result.

Expectation failed: ((try multi(1, 2)) → 2) == 3

[grynspan]

Duplicate of #162