[Issue 17909] New: Inherited aliases produce unlinkable objects in final classes

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=17909

          Issue ID: 17909
           Summary: Inherited aliases produce unlinkable objects in final
                    classes
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Mac OS X
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: jonathan at wilbur.space

In the following code, an alias is defined to allow all child classes to access
the member "beep" by the name "boop." The code below compiles just fine, links
just fine, and runs just fine.

abstract class Parent
{
    alias boop = beep;
    abstract string beep();
}

class Child : Parent
{
    override string beep() { return "BEEP"; }
}

void main ()
{
    import std.stdio : writeln;
    writeln((new Child()).boop);
}

However, if the Child class is made "final," the generated object(s) is(are)
unlinkable. From the command line, the error appears like so:

$ dmd ./sanity/test.d
Undefined symbols for architecture x86_64:
  "_D4test6Parent4beepMFZAya", referenced from:
      __Dmain in test.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Error: linker exited with status 1

This is all in the same file, so the fact that I even get a linker error in the
first place is pretty weird.

Is this expected behavior?

System information:

Uname -a: Darwin <hostname> 15.6.0 Darwin Kernel Version 15.6.0: Sun Jun  4
21:43:07 PDT 2017; root:xnu-3248.70.3~1/RELEASE_X86_64 x86_64
Operating System: Mac OS X El Capitan 10.11.6
Processor: 1.4 GHz Intel Core i5
DMD --version: DMD64 D Compiler v2.076.0-dirty
ld -v:
@(#)PROGRAM:ld  PROJECT:ld64-274.1
configured to support archs: armv6 armv7 armv7s arm64 i386 x86_64 x86_64h
armv6m armv7k armv7m armv7em (tvOS)
LTO support using: LLVM version 8.0.0, (clang-800.0.38)
TAPI support using: Apple TAPI version 1.30
clang --version:
Apple LLVM version 8.0.0 (clang-800.0.38)
Target: x86_64-apple-darwin15.6.0
Thread model: posix
InstalledDir:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

I may be able to test this on a Windows or a Linux machine soon, and I will
post the results if I do.

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