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d0bc2a8611
Strideable declares a default witness for Equatable and Comparable
extension Strideable {
@_inlineable
public static func < (x: Self, y: Self) -> Bool {
return x.distance(to: y) > 0
}
@_inlineable
public static func == (x: Self, y: Self) -> Bool {
return x.distance(to: y) == 0
}
}
This witness is implemented recursively because the expectation
is that Stride != Self. However, it is possible to implement
SignedNumeric and Strideable together and inherit this conformance
which will cause undefined behavior - usually a crash.
Provide an overload when Stride == Self and crash with custom message
that mentions that Equatable and Comparable have to be implemented
in this case.
- It's better than nothing.
44 lines
2.0 KiB
Swift
44 lines
2.0 KiB
Swift
// RUN: %empty-directory(%t)
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// RUN: %target-build-swift -emit-executable -DTEST_EQUATABLE -o %t/InvalidStrideableEq %s
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// RUN: ! %target-run %t/InvalidStrideableEq 2>&1 | %FileCheck %s --check-prefix=CHECK-EQUATABLE
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// RUN: %target-build-swift -emit-executable -DTEST_COMPARABLE -o %t/InvalidStrideableCmp %s
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// RUN: ! %target-run %t/InvalidStrideableCmp 2>&1 | %FileCheck %s --check-prefix=CHECK-COMPARABLE
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// REQUIRES: executable_test
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//
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// Check that a circular Strideable inheriting witnesses from Stdlib crashes
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// with a rich error message.
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//
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struct InvalidStrideable : Strideable, SignedNumeric {
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typealias Magnitude = InvalidStrideable
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init?<T>(exactly: T) where T : BinaryInteger { return nil }
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var magnitude: InvalidStrideable { return self }
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static func += (lhs: inout InvalidStrideable, rhs: InvalidStrideable) { }
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static func -= (lhs: inout InvalidStrideable, rhs: InvalidStrideable) { }
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static func *= (lhs: inout InvalidStrideable, rhs: InvalidStrideable) { }
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static func + (lhs: InvalidStrideable, rhs: InvalidStrideable) -> InvalidStrideable { return rhs }
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static func - (lhs: InvalidStrideable, rhs: InvalidStrideable) -> InvalidStrideable { return rhs }
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static func * (lhs: InvalidStrideable, rhs: InvalidStrideable) -> InvalidStrideable { return rhs }
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typealias IntegerLiteralType = Int
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init(integerLiteral : Int) {}
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typealias Stride = InvalidStrideable
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init() {}
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func distance(to rhs: InvalidStrideable) -> InvalidStrideable { return self }
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func advanced(by n: InvalidStrideable) -> InvalidStrideable { return self }
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}
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#if TEST_EQUATABLE
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// CHECK-EQUATABLE: fatal error: Strideable conformance where 'Stride == Self' requires user-defined implementation of the '==' operator
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_ = InvalidStrideable() == InvalidStrideable()
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#else
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// CHECK-COMPARABLE: fatal error: Strideable conformance where 'Stride == Self' requires user-defined implementation of the '<' operator
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_ = InvalidStrideable() < InvalidStrideable() // Will trap with error message
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#endif
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