43 lines
2.0 KiB
D
43 lines
2.0 KiB
D
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import imports.link14541traits;
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void main()
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{
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Tuple!(int, int) result;
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alias T = typeof(result);
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static assert(hasElaborateAssign!T);
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// hasElaborateAssign!(Tuple(int, int)):
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// 1. instantiates Tuple!(int, int).opAssign!(Tuple!(int, int)) [auto ref = Rvalue]
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// 2. instantiates swap!(Tuple!(int, int))
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// 3. instantiates hasElaborateAssign!(Tuple!(int, int))
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// --> forward reference error
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// --> swap!(Tuple!(int, int)) fails to instantiate
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// --> Tuple!(int, int).opAssign!(Tuple!(int, int)) [auto ref = rvalue] fails to instantiate
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// 4. instantiates Tuple!(int, int).opAssign!(Tuple!(int, int)) [auto ref = Lvalue]
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// --> succeeds
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// hasElaborateAssign!(Tuple(int, int)) succeeds to instantiate (result is 'true')
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// Instantiates Tuple!(int, int).opAssign!(Tuple!(int, int)) [auto ref = Rvalue], but
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// it's already done in gagged context, so this is made an error reproduction instantiation.
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// But, the forward reference of hasElaborateAssign!(Tuple(int, int)) is already resolved, so
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// the instantiation will succeeds.
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result = Tuple!(int, int)(0, 0); // --> 1st error reproduction instantiation
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result = Tuple!(int, int)(0, 0); // --> 2nd error reproduction instantiation
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// The two error reproduction instantiations generate the function:
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// Tuple!(int, int).opAssign!(Tuple!(int, int)) [auto ref = Rvalue]
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// twice, then it will cause duplicate COMDAT error in Win64 platform.
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}
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/+
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The point is, if instantiated contexts are different, two instantiations may cause different result.
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- The 1st Tuple.opAssign instantiation is invoked from hasElaborateAssign template with gagging.
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So it has failed, because of the circular reference of hasElaborateAssign template..
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- The 2nd Tuple.opAssign instantiation is invoked from main() without gagging.
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It does not have circular reference, so the instantiation should succeed.
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Therefore, the gagged failure should be overridden by the ungagged success.
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+/
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