[Issue 19091] __traits(compiles) and error in templated structs leads to missing symbol

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19091

--- Comment #12 from FeepingCreature <default_357-line at yahoo.de> ---
I have found a whole new manifestation of this bug!

struct Inner()
{
    bool opEquals(Inner) { }
}

struct Outer()
{
    Inner!() field;
    bool opEquals(Outer) { return field == field; }
}

void main()
{
    void nested()() { cast(void) Outer!()(); }

    static assert(__traits(compiles, nested()) == false);

    nested();
}

In 2.097.1, this results in an illegal instruction!

Building with master reveals that this is a compiled-out assert; it actually
errors with

core.exception.AssertError at src/dmd/e2ir.d(529): Assertion failure
----------------
??:? _d_assertp [0x55a6c3d0d8bd]
src/dmd/e2ir.d:529 _ZN13ToElemVisitor5visitEP10Expression [0x55a6c3bbe899]
src/dmd/visitor.d:66 _ZN7Visitor5visitEP8ErrorExp [0x55a6c3baf006]
src/dmd/expression.d:2026 _ZN8ErrorExp6acceptEP7Visitor [0x55a6c3aca97d]
src/dmd/e2ir.d:504 _Z6toElemP10ExpressionP7IRState [0x55a6c3bbe7d3]
src/dmd/e2ir.d:411 _Z10toElemDtorP10ExpressionP7IRState [0x55a6c3bbe41c]
src/dmd/s2ir.d:728 _ZN11S2irVisitor5visitEP15ReturnStatement [0x55a6c3be9ee3]
src/dmd/statement.d:1430 _ZN15ReturnStatement6acceptEP7Visitor [0x55a6c3b7e1b1]
src/dmd/s2ir.d:1537
_ZN11S2irVisitor14Statement_toIREP9StatementP7IRStateP9StmtStateI5blockE
[0x55a6c3bec1c3]
src/dmd/s2ir.d:786 _ZN11S2irVisitor5visitEP17CompoundStatement [0x55a6c3bea127]
src/dmd/statement.d:620 _ZN17CompoundStatement6acceptEP7Visitor
[0x55a6c3b7c815]
src/dmd/s2ir.d:1557 _Z14Statement_toIRP9StatementP7IRState [0x55a6c3bec2bf]
src/dmd/glue.d:1100 _Z25FuncDeclaration_toObjFileP15FuncDeclarationb
[0x55a6c3be1430]
src/dmd/toobj.d:311 _ZN9toObjFile9ToObjFile5visitEP15FuncDeclaration
[0x55a6c3bf6a64]
src/dmd/func.d:2817 _ZN15FuncDeclaration6acceptEP7Visitor [0x55a6c3b09cdd]
src/dmd/toobj.d:534 void dmd.toobj.toObjFile(dmd.dsymbol.Dsymbol,
bool).ToObjFile.visit(dmd.dstruct.StructDeclaration).__lambda2!(dmd.dsymbol.Dsymbol).__lambda2(dmd.dsymbol.Dsymbol)
[0x55a6c3bf7251]
src/dmd/dsymbol.d:105 void
dmd.dsymbol.foreachDsymbol(dmd.root.array.Array!(dmd.dsymbol.Dsymbol).Array*,
void delegate(dmd.dsymbol.Dsymbol)) [0x55a6c3a8739f]
src/dmd/toobj.d:534 _ZN9toObjFile9ToObjFile5visitEP17StructDeclaration
[0x55a6c3bf719e]
src/dmd/dstruct.d:451 _ZN17StructDeclaration6acceptEP7Visitor [0x55a6c3a86c6d]
src/dmd/toobj.d:827 void dmd.toobj.toObjFile(dmd.dsymbol.Dsymbol,
bool).ToObjFile.visit(dmd.dtemplate.TemplateInstance).__lambda2!(dmd.dsymbol.Dsymbol).__lambda2(dmd.dsymbol.Dsymbol)
[0x55a6c3bf7b35]
src/dmd/dsymbol.d:105 void
dmd.dsymbol.foreachDsymbol(dmd.root.array.Array!(dmd.dsymbol.Dsymbol).Array*,
void delegate(dmd.dsymbol.Dsymbol)) [0x55a6c3a8739f]
src/dmd/toobj.d:827 _ZN9toObjFile9ToObjFile5visitEP16TemplateInstance
[0x55a6c3bf7b0e]
src/dmd/dtemplate.d:7504 _ZN16TemplateInstance6acceptEP7Visitor
[0x55a6c3ab4cd1]
src/dmd/toobj.d:1008 _Z9toObjFileP7Dsymbolb [0x55a6c3bf69ca]
src/dmd/glue.d:522 _Z10genObjFileP6Moduleb [0x55a6c3bdf9d3]
src/dmd/glue.d:137 void dmd.glue.generateCodeAndWrite(dmd.dmodule.Module[],
const(char)*[], const(char)[], const(char)[], bool, bool, bool, bool, bool)
[0x55a6c3bde396]
src/dmd/mars.d:571 int dmd.mars.tryMain(ulong, const(char)**, ref
dmd.globals.Param) [0x55a6c39f92a5]
src/dmd/mars.d:953 _Dmain [0x55a6c39fa851]

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