[Issue 14966] Comparing two std.xml.Document result in infinite recursion

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=14966

--- Comment #2 from Jacob Carlborg <doob at me.com> ---
It's so obvious, that's why I didn't provide a test case. The content of the
XML doesn't matter. I added a test case with a stack trace at the bottom.

I think the issue is that implementation of Document.opEquals:

override bool opEquals(Object o)
{
    const doc = toType!(const Document)(o);
    return
        (prolog != doc.prolog            ) ? false : (
        (super  != cast(const Element)doc) ? false : (
        (epilog != doc.epilog            ) ? false : (
    true )));
}

I suspect the issue is the super call. I'm guessing since the implementation of
==/!= was changed to call object.opEquals, which then calls opEquals on the
object. The object will be dynamically resolved to Document and then call
Document.opEquals again, resulting in infinite recursion. I was planning to ask
about this in the newsgroup if this is a regression but forgot about it.

Test case:

$ cat main.d
import std.xml;

void main()
{
    auto xml = `
        <?xml version="1.0" encoding="UTF-8"?>
        <foo></foo>
    `;

    auto a = new Document(xml);
    auto b = new Document(xml);
    auto c = a == b;
}
$ dmd main.d && lldb main
(lldb) target create "main"
Current executable set to 'main' (x86_64).
(lldb) r
Process 68379 launched: '/Users/jacob/development/d/main' (x86_64)
Process 68379 stopped
* thread #1: tid = 0x4ad39f, 0x00000001000156f4 main`_d_isbaseof2 + 8, queue =
'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=2,
address=0x7fff5f3fffa8)
    frame #0: 0x00000001000156f4 main`_d_isbaseof2 + 8
main`_d_isbaseof2:
->  0x1000156f4 <+8>:  pushq  %rbx
    0x1000156f5 <+9>:  pushq  %r12
    0x1000156f7 <+11>: pushq  %r13
    0x1000156f9 <+13>: pushq  %r14
(lldb) bt
* thread #1: tid = 0x4ad39f, 0x00000001000156f4 main`_d_isbaseof2 + 8, queue =
'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=2,
address=0x7fff5f3fffa8)
  * frame #0: 0x00000001000156f4 main`_d_isbaseof2 + 8
    frame #1: 0x00000001000156d1 main`_d_dynamic_cast + 45
    frame #2: 0x00000001000361b8
main`D3std3xml31__T6toTypeTxC3std3xml8DocumentZ6toTypeFC6ObjectZxC3std3xml8Document
+ 20
    frame #3: 0x00000001000322f9 main`D3std3xml8Document8opEqualsMxFC6ObjectZb
+ 21
    frame #4: 0x0000000100001a59 main`D6object8opEqualsFC6ObjectC6ObjectZb +
109
    frame #5: 0x00000001000019e5 main`D6object8opEqualsFxC6ObjectxC6ObjectZb +
13
    frame #6: 0x0000000100032334 main`D3std3xml8Document8opEqualsMxFC6ObjectZb
+ 80
    frame #7: 0x0000000100001a59 main`D6object8opEqualsFC6ObjectC6ObjectZb +
109
    frame #8: 0x00000001000019e5 main`D6object8opEqualsFxC6ObjectxC6ObjectZb +
13
    frame #9: 0x0000000100032334 main`D3std3xml8Document8opEqualsMxFC6ObjectZb
+ 80
    frame #10: 0x0000000100001a59 main`D6object8opEqualsFC6ObjectC6ObjectZb +
109
    .
    .
    .
    frame #196537: 0x0000000100001a59 main`D6object8opEqualsFC6ObjectC6ObjectZb
+ 109
    frame #196538: 0x0000000100001236 main`_Dmain + 102
    frame #196539: 0x0000000100016b1c
main`D2rt6dmain211_d_run_mainUiPPaPUAAaZiZ6runAllMFZ9__lambda1MFZv + 40
    frame #196540: 0x0000000100016a61
main`D2rt6dmain211_d_run_mainUiPPaPUAAaZiZ7tryExecMFMDFZvZv + 45
    frame #196541: 0x0000000100016ac1
main`D2rt6dmain211_d_run_mainUiPPaPUAAaZiZ6runAllMFZv + 45
    frame #196542: 0x0000000100016a61
main`D2rt6dmain211_d_run_mainUiPPaPUAAaZiZ7tryExecMFMDFZvZv + 45
    frame #196543: 0x00000001000169d4 main`_d_run_main + 504
    frame #196544: 0x0000000100001254 main`main + 20
    frame #196545: 0x00007fff9a0295c9 libdyld.dylib`start + 1
    frame #196546: 0x00007fff9a0295c9 libdyld.dylib`start + 1
(lldb)

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