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[SR-2636] + Operator fails to infer type for more than 2 force unwrapped values #45241

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swift-ci opened this issue Sep 14, 2016 · 5 comments
Closed

[SR-2636] + Operator fails to infer type for more than 2 force unwrapped values #45241

swift-ci opened this issue Sep 14, 2016 · 5 comments
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@rudkx
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself type checker Area → compiler: Semantic analysis

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Previous ID SR-2636
Radar None
Original Reporter wattson12 (JIRA User)
Type Bug
Status Closed
Resolution Duplicate

Attachment: Download

Environment

Xcode 8

Additional Detail from JIRA
Votes 1
Component/s Compiler
Labels Bug, TypeChecker
Assignee @rudkx
Priority Medium

md5: b79c6133c0059751b9920db443c6f49b

duplicates:

  • SR-1122 Failure to typecheck chain of binary operators on force-unwrapped values

is duplicated by:

  • SR-3134 force-unwrapping fails mysteriously when interleaved with + operators

Issue Description:

When summing values pulled (and force unwrapped) from a dictionary, Swift doesn't pick up the types when adding more than 2 values.

e.g. given

let menu: [String: Double] = ["pizza": 10.99, "ice cream": 4.99 , "salad": 7.99]

These are both fine:

let singleValue = menu["pizza"]!
let twoValueSum = menu["pizza"]! + menu["salad"]!

And this fails:

let threeValueSum = menu["pizza"]! + menu["salad"]! + menu["ice cream"]!
Playground execution failed: error: TestBetaPlayground.playground:7:36: error: ambiguous reference to member '+'
let threeValueSum = menu["pizza"]! + menu["salad"]! + menu["ice cream"]!

To give some extra info, all of these are valid

let threeValueSumFromTwoValueSum = twoValueSum + menu["ice cream"]!
print("The total cost of the meal = \(menu["pizza"]! + menu["salad"]! + menu["ice cream"]!)")
let sumWithAddedZero = menu["pizza"]! + menu["salad"]! + menu["ice cream"]! + 0
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Comment by Richard Cook (JIRA)

I'm trying this in a playground. Version 8 (8A218a) and it shows the following compiler error:

var menu = ["coffee": 0.50, "pizza": 10.99, "ice cream": 4.99]

var totalCost = menu["coffee"]! + menu["pizza"]! + menu["ice cream"]!

print("The total cost of three items is \(totalCost)")

Playground execution failed: error: MyPlayground.playground:26:21: error: cannot subscript a value of type 'inout [String : Double]' (aka 'inout Dictionary<String, Double>')
var totalCost = menu["coffee"]! + menu["pizza"]! + menu["ice cream"]!

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Comment by Sam Watts (JIRA)

awhig (JIRA User) Not sure if that is the same issue, but does seem related. If i change menu to a let, the error is the same as the one I mentioned above

When using var the totalCost line is fine adding only 2 values, but adding the third results in the subscript error you posted

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Comment by Sam Watts (JIRA)

Also the same fix of adding + 0 somewhere in the totalCost line removes the subscript error

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Comment by Steve B (JIRA)

May not help but this is another verbose workaround.

let cost = Double(menu["pizza"]!) + Double(menu["ice cream"]!) + Double(menu["salad"]!) // explicit cast to type works

This problem also occurs with other dictionary types. ie. [String: Int].

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swift-ci commented Dec 9, 2016

Comment by David Friberg (JIRA)

Possible duplicate of SR-1122.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself type checker Area → compiler: Semantic analysis
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