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Previously, we were binding optional l-values only when performing an access. This meant that other evaluations emitted before the formal access were not being short-circuited, even if the language rules said they should be. For example, consider this code:: var array : [Int]? = ... array?[foo()] = bar() Neither foo nor bar should be called if the array is actually nil, because those calls are sequenced after the optional-chaining operator ?. The way that we currently do this is to project out the optional address during formal evaluation. This means that there's a formal access to that storage beginning with the formal evaluation of the l-value and lasting until the operation is complete. That's a little controversial, because it means that other formal accesses during that time to the optional storage will have unspecified behavior according to the rules I laid out in the accessors proposal; we should talk about it and make a decision about whether we're okay with this behavior. But for now, it's important to at least get the right short-circuiting behavior from ?. Swift SVN r23608
22 lines
669 B
Swift
22 lines
669 B
Swift
// RUN: %target-run-simple-swift | FileCheck %s
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var x: Int! = 0
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x! = 2
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println(x) // CHECK: 2
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x!++
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println(x) // CHECK-NEXT: 3
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var sequences = ["fibonacci": [1, 1, 2, 3, 0]]
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println(sequences) // CHECK-NEXT: [fibonacci: [1, 1, 2, 3, 0]]
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sequences["fibonacci"]![4] = 5
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println(sequences) // CHECK-NEXT: [fibonacci: [1, 1, 2, 3, 5]]
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sequences["fibonacci"]!.append(8)
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println(sequences) // CHECK-NEXT: [fibonacci: [1, 1, 2, 3, 5, 8]]
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func printAndReturn(x: Int) -> Int { println(x); return x }
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println("optional binding") // CHECK-NEXT: optional binding
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var y: Int? = nil
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y? += printAndReturn(4)
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println("done with binding test") // CHECK-NEXT: done with binding test
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