From http://stackoverflow.com/q/33553013/21501: ///////////// test.d //////////// import std.typecons; struct Node { int value; NullableRef!Node left, right; } void main() { Node n; } ///////////////////////////////// Introduced in https://github.com/D-Programming-Language/dmd/pull/4820
Reduced: //////// test.d //////// struct NullableRef(T) { inout(T) get() inout { assert(false); } alias get this; } struct Node { NullableRef!Node n; } ////////////////////////
(In reply to Vladimir Panteleev from comment #1) > Reduced: > > //////// test.d //////// > struct NullableRef(T) > { > inout(T) get() inout > { > assert(false); > } > > alias get this; > } > > struct Node > { > NullableRef!Node n; > } > //////////////////////// An infinite recursive analysis happens in the implicitly generated member function: bool Node.__xopEquals(ref const Node p, ref const Node q) { return p == q; } The equality test p == q is expanded to p.tupleof == q.tupleof, and it's equivalent with p.n == q.n. Because of the alias-this definition in NuallbeRef!Node, the comparison is delegated to the return of get member function, then it's rewritten to p.n.get() == q.n.get(). Finally, we'll go into an endless circle. Now I have a local patch to detect the circle. But I'm yet not sure how compiler should work for the following code. void main() { Node node; assert(node == node); // ? } I think the Node equality should be either: 1. make an error 2. implicitly fallback to bitwise comparison
https://github.com/D-Programming-Language/dmd/pull/5274
Commits pushed to stable at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/2f0cc57aa71a6ff67f27ec3727841ec756c843fb fix Issue 15292 - Segmentation fault with self-referencing struct / inout / alias this If you read the `expr.aliasthis` to `expr.tupleof`, you could understand that the mechanism to detect recursive tupleof expansion is same with for alias-this'es. https://github.com/D-Programming-Language/dmd/commit/dff37b9526d154f844f7a35340015ef3e93975d3 Merge pull request #5274 from 9rnsr/fix15292 [REG2.068.0] Issue 15292 - Segmentation fault with self-referencing struct / inout / alias this
Commits pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/2f0cc57aa71a6ff67f27ec3727841ec756c843fb fix Issue 15292 - Segmentation fault with self-referencing struct / inout / alias this https://github.com/D-Programming-Language/dmd/commit/dff37b9526d154f844f7a35340015ef3e93975d3 Merge pull request #5274 from 9rnsr/fix15292