How to Report a Bug to Microsoft

So you found a bug in one of Microsoft’s great works of software art. What do you do now? I realized that there isn’t a nice step-by-step guide online, so I will give you the low-down on how this process works. It’s not straightforward — Microsoft is a large company, and has probably thousands of calls or reports each day from people who don’t know how to open the File menu. Unfortunately, for those of us in the software development industry, there isn’t a quick or easy way to report actual bugs.

The Bug

My bug that I found has to do with Excel 2016. At my company, we have many spreadsheets that use a feature in Excel called “Web Queries“. These allow one to download a web page, or a table that is on the web page, into cells in your excel document.

In my particular case, I am using this feature to connect our internal job tracking system that I developed to spreadsheets that are used for calculating pricing and energy savings (our company makes energy savings updates to refrigeration systems), and upload that result back to the tracking system.

In Excel 2010, and Excel 2013, this works well. However, I have discovered recently that in Excel 2016 (at least for Office 365 version 16.0.8067.2115) the web query downloads the entire web page and not the selected table. This means lots of extra data is coming into the spreadsheet that is not expected, overwriting other cells in the sheet, and causing many things not to work.

Step 1: Search for Existing Reports, Reduce Use Case

The Internet is great for sharing misery of issues with applications that have known limitations. Look for any help on Excel, there’s usually a boatload of hits on google. However, in this case, I found surprisingly little online, maybe a few that could be related, but people have worked around it with VBA macros, and other things. I don’t have that luxury, since the sheer number of files I would have to update makes this very time consuming.

Any good software engineer knows, before reporting a bug to the organization that owns the software, the most helpful thing you can do is reduce it to the minimal case. In my case it is easy. I created an html page that had one table on it:

Using excel, I created a new document in 2016, and added the web query. The way this is done is to select the “From Web” button on the Data ribbon:

This will bring up a web browser (it’s actually Internet Explorer), allowing you to select both the page, and any sub-table you wish. Here I’ve pointed at the aforementioned web page, and selected the single table for import:

Finally, click the Import button at the bottom, and you get the error I was talking about:

The correct result should be to import only the table data, and not the “before” or “after” text. Here is how it looks on Office 2010:

Now that we have a very reduced, and obvious bug, we can proceed to the next level, which is contacting Microsoft directly.

Level 1: Microsoft Chatbot

Microsoft has a chat bot that will try to help you with answers to questions using some advanced AI. It doesn’t take long to defeat this foe, as this is your standard search of the knowledge base, and you can simply say “No, this doesn’t answer my question”. Eventually, it will attach you to a live agent in the chat window.

Note to Reader: I did not capture any of these sessions as screenshots or logs, unfortunately, so I will describe as best I can the interactions between me and the support staff.

Level 2: Installation Support

Regardless of what you have told the chatbot, or how technical you sound, the first level of Live human support is an installation technician. These are the people who can service the “I can’t find the File menu” support requests. Understandably, these people have much automation at their disposal, and training in how to deal with these kinds of issues. You will get responses to your questions such as “I understand that you are having problems with your web queries in Excel. I’m so sorry for your experience, I’ll be asking you a series of questions to assist you in fixing this issue” and “I understand that you think this is a bug in Excel. I’m so sorry you feel that way, I’ll ask you a few more questions to assist you in fixing this issue.”

The chinks in the armor of these combatants are plain to see — they have buttons to click that repeat what you say, and eventually show the nature of their game. After a few button clicks and repetition, you get something along the lines of “Your problem needs to be handled by the next level of support. Unfortunately, this cannot be done over a chat session. The best option is to call …” and so on. Congratulations, you have graduated to the next world of the Microsoft Support Infrastructure! Here is where you now need to come out of that computer and into the real world with real people.

Level 3: Office 365 Installation Technician

After being on hold for about 5 minutes, you finally get to show them that you actually have technical experience, and explain the real issue to a living breathing person, not augmented with automated responses. The technician in this case is not trained really on the underlying technology of Excel or any other Microsoft products. Finding the File menu is just about all they know. It doesn’t take long to KO this Glass Joe, and move on to the next level. What you are looking for here is “I’m not trained in this area, so I’m going to escalate you to Level 2 technical support.” Note that at Microsoft, even though we are on Level 3, the technicians are trained to attempt deception at every turn. Saying you were really only on Level 1 is a clever use of psychology to try and dampen your spirits. But cheer up, we will prevail!

Level 4: “Level 2” Technician

At this point, you are on hold, and your phone call is stretching past 30 minutes. This is another technique employed by the technicians. Usually you will hear some great news about Windows 10 on the hold line, “now that it is released”, and some of the amazing things you can accomplish. The message here is clear “Microsoft is huge, and you are just one lowly Office 365 licensee. You really should hang up if you know what’s good for you.” I know you have things to do, and it is tempting to give up, but patience is a virtue, and Windows 10 is pretty amazing1, so don’t give up yet!

Finally when you achieve a connection to the L2T, you will finally have the ear of a technical person. “Finally,” you think, “someone who will understand this issue.” This person will use a web applet to actually take over your Windows computer and allow you to show him exactly the issue. You use your minimal test case to prove beyond a doubt that the issue is definitely caused by Office 2016.

The truth is, this person does understand your issue, but his job is not to help you report it. His job is to find loopholes — Loopholes that allow Microsoft to defeat you and send you back to the File menu-finding engineers.

L2T: Can I have your microsoft id?

Me: Yes, it’s redacted@redacted.com

L2T: Let me look up your information. It shows here you have Office 365 Home. We are actually a support office for Commercial users of our product. We have a special division of support that can help you with your Office 365 issues. Let me connect you.

Level 5: The Deflection Specialist

At this point, you have been on the phone for about 45 minutes, and the impatience is growing inside you. You have suffered your first “defeat”, but really it was a victory. Again remember, Microsoft’s deception training is very prevalent in all their support staff. Even though it seems you have been shoved back to the File-menu engineers, you have actually been passed to a special department of Office 365 support called the “Deflection Department”. This department’s job is basically to lie. They make up any excuse or technical jargon to try and get you off the phone.

After you explain your bug2:

Deflection Specialist: OK, so you have a file that works with 2010, but not in 2016? Was this file created in Office 2010?

Me: Well, actually it’s probably older than that…

DS: Oh, sir, unfortunately, the software was completely rewritten in 2013, so files created before that version aren’t compatible with later versions.

Me: OK, so what is the upgrade path? How do I make the file work for 2016?

DS: You can’t, you need to recreate the file in 2016.

Me: But I have a brand new file I created with 2016, and it has the same issue.

DS: How many versions of office do you have installed on this computer?

Me: Well, I just installed 2016, but 2010 still is on there.

DS: That is probably the issue, it isn’t supported to run more than one version of Excel on the same system.

Me: But other users who only have 2016 also have this issue.

DS: By the way I wanted to let you know, this issue you are having is being widely reported right now, and our team is working on it. I suggest you wait 48 hours and see if any updates come out to fix the issue.

Me: OK, so you are telling me that many people are calling in to Microsoft to report this Web Query Issue?

DS: Do you know the exact version of office you are running? Here, let me log into your computer to see.

[At this point, the Deflection Specialist logs into my computer by having me download the same app that the Level 2 Technician had me download.]

DS: Yes, see, you have both office 2010 and 2016 installed, let me remove that.

At this point, she removes Office 2010. Note that I actually am running Windows 10 on a VM inside my Mac, and have created a snapshot from before I installed 2016 to work on this problem, so I’m not objecting at all to her removing the only working version of Excel from my system. It is wise to have a back up plan for when you start this whole bug reporting process.

The secret to defeating the Deflection Specialist is to keep talking. Keep asking questions, keep insisting that your problem is not solved, and that she needs to pay attention to the obvious bug. At this point, your call is over an hour, and irritation is noticeable in your voice. This is a good thing, she can sense this, and will then say:

DS: I’m actually not trained on this part of Excel, so I’m going to send you to a Level 2 technician…

Me [Interrupting]: But is it a Commercial Level 2 technician? Because I’ve already spent over 1 hour on the phone, and I’ve talked to Office 365 technicians and Level 2 commercial technicians, and they keep sending me back and forth.

DS: No sir, I assure you, this is a department that specializes in Office 365 issues, and will be able to solve your problem.

After the final lie, the DS has given up, and sends you to the next level.

Level 6: “Level 2” Technician, World Circuit

This enemy is just like the original Level 2, except she gets right to the chase. You don’t get to her unless you have an actual provable bug in the product, so she doesn’t waste any time going through the motions. She still asks for the details of your bug, but then immediately asks for your authorization:

L2T: Do you have a case number?

Me: I probably should by now, I’ve been on the phone for 70 minutes, and have been passed back and forth between level 1 and level 2 support, each claiming that they can’t help me.

L2T: So sorry to hear that. Are you using Office 365 Home edition, or Business.

Me: I’m pretty sure it doesn’t matter

L2T: I need to know which version, as we service commercial…

Me: The last person I spoke with said that you would be someone that was able to understand and fix this issue. Is there anyone at Microsoft that understands Office?

L2T: Why don’t you give me your Live ID and I can look up your product version.

[A few minutes later]

Me: I’ve been sent to them THREE TIMES, and they keep sending me back to your department, I don’t think they can help me.

L2T: Sorry sir, we only service Commercial customers here, and they will be able to help you with this…

Me [Interrupting]: You can’t keep sending me over there, I want to make sure that this person knows how to deal with this bug.

L2T: I will first conference this person in, and make sure they understand the issue before letting you go, is that OK?

Me: OK, we can try that.

If you have made it this far, congratulations! Your veins may be about to burst out of your forehead, and your polite manner has probably disintegrated into terse annoyance, but the paydirt is about to come. You will now face the final challenge in the Microsoft Support Infrastructure…

Level 7: The Link Engineer

Not going to sugar-coat this, this is the final stop in your phone call. I’ll just tell it like it happened:

L2T: I have confirmed that the technician understands your issue, and will be able to help, so are you OK with me dropping off the line?

Me: Yes, thank you. [L2T hangs up]

Link Engineer: Hi, can you please describe your problem

[Repeat same description]

LE: Thank you for telling me that. Unfortunately, our office is not trained to handle these types of questions, so I’m going to give you a link to go to…

Me: Are you freaking kidding me? Does ANYONE at Microsoft know how Office even freaking works???!!! I’ve been on the phone for 80 MINUTES, and you are going to send me to a Knowledge Base article???!

LE: Sorry sir, but if you go to answers.microsoft.com…

Me: I just want to report this bug! It’s a bug, confirmed it is in Office 2016!!! Do you care about having bugs fixed in your product?!! Some answers page isn’t going to help me! I’m sick of this, you have no clue what you are talking about.

Now, hang up the phone. Don’t just hang it up. Slam it down so they know you are pissed.

Final Level: Write an Angry Blog Post

Yep, that’s it. Write one just like this one. If there’s anything Microsoft or large companies like them understand, it’s that bad PR on the Internet, especially when written in a sassy, clever fashion with references to old video games, will get people’s attention. This will persuade them to immediately start working on the bug “reported”, and it should be fixed by the next version3.

Some questions you may have, and I’ll answer them:

1. Do I have to go through the entire Microsoft Support Infrastructure gauntlet to write an angry post about my bug?

Yes you do. If you don’t have a long horrible story about phone support, it’s not as interesting, and will not gain any attention.

2. Did you know that newer versions of Excel have “Power Query” capability, and that the “Web Query” feature is pretty much obsolete?

Yes, I know that. The Web Query feature is obviously meant to be supported in 2016, as it’s in the UI. And Microsoft is famous for not breaking backwards compatibility. I also have several hundred spreadsheets that would have to be updated. Not going to do it.

3. Why do you have hundreds of spreadsheets? Why not just merge them into one maintainable spreadsheet where you could fix the problem in one place?

Because shut up.

4. What if I have paid for support from Microsoft?

Then you can report my bug for me directly. Why haven’t you? It’s really obvious and straightforward. Please?

A Final Note: I know that there are some good people working at Microsoft (with the exception of the DS), and I took some creative license in the snark describing this phone support. I really do hope they find and fix the issue, and don’t mind this ribbing.

UPDATE: Since this has been posted on HackerNews and reddit, some very nice folks at Microsoft have chimed in with some helpful tips (and all of them polite). First, I want to thank one in particular who reproduced my issue and filed a bug in their internal system. So yes, it works!

Second, here is a collection of ways that are probably better than the approach I took:

  • Use the feedback button in your Office 2016 product (I hadn’t seen this before, but looks like a way to submit a pretty detailed bug report).
  • Use office365.uservoice.com, for which Microsoft has many places to suggest features. The news from the insiders is that the developers patrol those regularly.
  • Even though I was in a rotten mood and hung up, the last technician (the Link Engineer) was trying to send me to answers.microsoft.com. Apparently, this is also recommended as a way to get in touch with developers, but I have to say from my experience seeing some of the conversations on there, they aren’t always that good.
  • If you are working with an open source Microsoft product, try to find it on github and submit an actual bug there (or even better submit a pull request to fix it).

Thank you everyone with tips, it was actually very good to see all the genuine sympathy and offers of help, especially from MS employees. Cheers!

  1. When compared to Windows Vista or Windows 8 []
  2. Note: this isn’t verbatim, but I kid you not, this was the gist of our conversation []
  3. disclaimer: I have no idea if this is going to work, but it really should []

Have your Voldemort types, and keep your disk space too!

A recent issue I discovered (and no doubt has been encountered before) is that using Voldemort types in D can result in insane symbol bloat. However, at DConf 2016, a presentation by Vladimir Panteleev gave me an idea to help solve the problem. This allows one to create a Voldemort type, but cuts out most of the template bloat that can impede your project.

Voldemort Wrappers

Voldemort wrappers are a way to create chain constructed types — types where you wrap one type in another type, but the construction of the wrapper is done via an Implicit Function Template Instantiation (IFTI) factory function. The type itself is defined inside the function, and so is not able to be named by an external entity (hence the term Voldemort). This is a very nice encapsulation, because the type doesn’t interfere with any other symbols, and all creation of the type itself is funneled through the approved factory function.

An example of a Voldemort Wrapper is the chain function from Phobos. chain takes 2 ranges with the same element type and makes a range that will traverse the first, and then the second, as if they were one range (for more info on ranges, I recommend reading Ali Çehreli’s chapter on the subject). The full chain function gives us lots of niceties, such as implementing all the common features between the two ranges. However, for demonstration purposes, we will write an inputChain function that only works on like-typed input ranges:

Now, we can write a simple test that chains together ranges without any allocation!

And the result:

$ ./testchain
hello, world!

This is all pretty straightforward stuff, and isn’t groundbreaking. But what is hidden from you here is the alarming space-cost for Voldemort wrapper types.

Exponential Symbols

Let’s print out the name of the nameless type (yes, it does still have a name, even though you can’t access it). This is a bit tricky, because simply printing typeof(ch).stringof results in the name Chain. However, this isn’t what we want, what we want is the fully qualified and instantiated type name. The easiest way to get this is to create an exception with the type name in it:

The result of running this with our previous main file is a stack trace that starts with:

$ ./testchain
object.Exception@simplechain2.d(13)
----------------
4   testchain                           0x00000001063efa24 pure @safe dchar simplechain.inputChain!(immutable(char)[], immutable(char)[]).inputChain(immutable(char)[], immutable(char)[]).Chain.front() + 144
...

Here is the Chain type in a “nicer” format (I have replaced immutable(char)[] with the more commonly known alias string):

simplechain.inputChain!(string, string).inputChain(string, string).Chain

Here, we can see that the type of ch isn’t just Chain, it contains the full signature of the function Chain comes from1 . The reason you see inputChain twice, is because inputChain is a template function. There are two symbols, one for the template (denoted by the instantiation symbol ‘!‘), and one for the function itself, which we will cover later. While this in itself isn’t extremely troubling (and actually makes a lot of sense), the trouble becomes apparent when you try to chain 3 strings together (using UFCS):

Compiling and getting the exception, the type of ch is now:

simplechain.inputChain!(
    simplechain.inputChain!(string, string).inputChain(string, string).Chain,
    string)
 .inputChain(
    simplechain.inputChain!(string, string).inputChain(string, string).Chain,
    string)
.Chain

I’ve tried to use indents to show you the pieces of this. First, we have the template. The template takes two parameters (two different ranges in fact). The first template parameter is the resulting type of the first inputChain call (you should recognize this from before). Note that this contains not only the template instantation, but the full signature of the function call as well. The second parameter is simply another string. And we get the repeated information for the function parameters.

If you continue this pattern, perhaps with more inputChain calls tacked onto the end of the call (as one would do with range pipelines in Phobos), then you can see how this will get progressively worse. The first argument to each call is going to be a recursive expansion of each previous call. I believe the growth of the symbol name is on the order of O(2n), meaning we have exponential growth. However, for name mangling, the expansion is O(3n), because unshown here is the return type of each level of function.

Abandoning the Dark Lord

So with such growth, a small range pipeline of Voldemort wrappers can add up to megabyte-long symbol names. But notice that the type itself is dependent only on the template parameters, not the function parameters2.

We can solve the problem by moving the struct outside the function itself, to be included in the module namespace. Make this a private struct, and repeat all the template paraphernalia, and we have a “solution”:

And the resulting type:

simplechain.Chain!(simplechain.Chain!(string, string).Chain, string).Chain

Not too bad as a name, and this solves the exponential growth. But we have lost all the niceties that make Voldemort types so attractive — avoiding namespace pollution, avoiding repeating template specification, and encapsulation. This solution leaves a lot to be desired.

Using eponymous templates

So let’s look at a better way, that allows us to keep the benefits of Voldemort types, but without the baggage. In D, all templated functions, enums, types, etc. are actually a short form of a special type of template called an eponymous template. When you compile inputChain, the compiler really treats it as something that looks like this:

An eponymous template function still works with IFTI, so it’s equivalent to the original. However, now we have access to a namespace that we didn’t have before — the space inside the template, but outside the function itself. As shown by Vladimir Panteleev’s DConf 2016 talk, access to this space is forbidden by the compiler to outside functions and types because it always resolves to the eponymously named member.

So let’s put our struct there:

And the resulting type:

simplechain.inputChain!(simplechain.inputChain!(string, string).Chain, string).Chain

Note that the Chain type is safely buried inside the template namespace, without providing access to any outside callers. If you used the above type name, you would get a compiler error.

I call this the Horcrux3 method. If we compare this to Voldemort, it’s pretty much on par with all the features, except Horcrux wrappers do not support access to the function call stack or any definitions inside the function (unless you move them into Horcrux space as well), and the declaration is a little clunky. However, you may have some advantages. For example, if you had overloaded functions that return the same type, they could both be in the same template, and share the type externally, making them even less repetitive than the equivalent Voldemorts. You could also put unit tests inside that would now have access to the structs directly.

There is some effort to fix the compiler to avoid creating such huge symbols, but until this happens, I will be splitting my functions Horcrux style.


Here is the Github Gist with all the code included in the article.

  1. Note that yes, the mangled symbol name (the one actually stored in the object file) reflects all of these pieces. I’m using exceptions to print out the name because they are easier to read and understand, but the same problem exists with mangled names as well. []
  2. In D, there is such a thing as a nested struct. Such a struct can utilize the stack frame of the function itself, giving access to variables and other definitions inside the function []
  3. If you don’t get this, then you need to read more Harry Potter []

Import Changes in D 2.071 [Updated]

Note: This post has been updated on 8/29/2016 with new information on mixin template imports.

In the upcoming version of D, several changes have been made to the import system, including fixes for 2 of the oldest bugs in D history.

There’s bound to be a lot of confusion on this, so I wrote this to try and explain the rules, and the reasoning behind some of the changes. I’ll also explain how you can mitigate any issues you have in your code base.

Bugs 313 and 314

Links: 313 and 314

Description

Private imports are not supposed to infiltrate the modules they are imported in. If you import a, and a imports b privately, then you should not have any access to b‘s symbols. However, before this was fixed, you could access b symbols via the Fully Qualified Name. A FQN is where you list all packages, including subpackages, separated by dots, to access a symbol. For example std.stdio.writeln.

In addition, when importing a module using static, renamed, or selective imports, the imported symbols were incorrectly made public to importing modules.

An example:

With 2.070 and prior versions, compiling this works just fine. With 2.071 and above, you will get either a deprecation warning, or an error.

Note that the private qualifier is only for illustration. This is the default import protection for any imports.

For an example of how selective imports add public symbols:

With 2.070, this compiled just fine. However, printf is supposed to be a private symbol of module ex2_a. With 2.071 and above, this will trigger a deprecation warning. In the future, the code will trigger an error.

Selective imports and FQN

A combination of both 313 and 314 is when you use a selective import, and expect the Fully Qualified Name to also be imported. This is not what the selective import was supposed to do, it was only supposed to add the symbols requested.

An example:

In this example, std.stdio.writeln is not actually supposed to be imported, only write is supposed to be imported (and even the FQN std.stdio.write isn’t imported!). We have to import std.range, because otherwise this would not compile (ironically, the package std is not imported by the selective import unless there is another import of the FQN).

In 2.070, this produces no warning or error. In 2.071 and beyond, this will produce a deprecation warning, and eventually an error.

Fixing problematic code

In order to fix such code, you have to decide what was intended. If your code really was supposed to publicly import the symbols, prepend public to the import statement. This brings all the symbols imported into the namespace of the module, so any importing module also sees those symbols. In our example 2 above, this would mean adding public to the import statement in ex2_a.d

If the imported module was not supposed to publicly expose the symbols, then you need to fix all importing modules with this problem. In our example, this would mean adding import core.stdc.stdio; to the top of ex2_main.d.

In the case of accidentally exposing the FQN of symbols that were privately imported, this is typically an issue with the importing module, not the imported one. In this case, you need to add an import. In our example 1 case, this would mean adding an import for ex1_a module to ex1_main.d.

For example 3, you can achieve the original behavior by both selectively importing the symbol, and statically importing the module. Just add static import std.stdio; to your scoped imports. Alternatively, you can add writeln to the selectively imported symbols, and use the unqualified name instead of the FQN.

For an example of how Phobos was fixed for this problem (there were thousands of messages in every build with deprecation warnings), see the PR I created.

Bug 10378

Links: 10378 Pull Request

Description

Another import-related bug fix is to prevent unintentional hijacking of symbols inside a scoped import. Such imports are not at module level, and import inside a function or other scope. These imports are only valid within the scope. Prior to 2.071, such imports were equivalent to importing every symbol in the imported module into the namespace of that scope. This overrode any other symbol in that namespace, including local variables in outer scopes. An example:

In 2.070 and prior, the assert above used ex4_a‘s definition of foo, not the local variable. In 2.071 and beyond, the local foo has precedence. The precedence rules work like this:

  1. Any local symbols are examined first. This includes selective imports which are aliased into the local scope.
  2. Any module-level symbols are examined.
  3. Any symbols imported are examined, starting with the most derived scope imports, all the way to module-level imports.

Note that this may be a breaking change, as demonstrated by the example.

Why did we change this?

This was changed because any symbol added to an import can drastically affect any code that uses non-selective scoped imports, hijacking the symbol in ways that the author cannot predict. While there is still potential for hijacking, since scoped imports override any module-level or higher level scoped imports, at least symbols that are locally defined are not affected. These are the symbols under direct control of the author of the module, and they should always have precedence.

A common change to a module is to move imports inside the scope of functions or types that are the only users of that import. This helps avoid namespace pollution. However, given that local module functions had precedence over imported ones, but scoped imports would take precedence away, this move was not always what the user intended. For this reason, module functions now always have precedence over non-selective scoped imports.

Fixing problematic code

This one is a little more nuanced. It may be that you wished to override the local symbols! In this case, use a selective import. Selective imports alias the symbols selected into the local scope, overriding any other symbols defined at that point. In our example, if we expected foo to refer to ex4_a.foo, then we would use an import like this: import ex4_a: foo;

In addition, you can use the FQN instead of using the simple name. I would recommend using a static or renamed import in that case.

Imports from mixin templates1

Links: Forum discussion, issue 15925

Description

A somewhat controversial change with 2.071 is the effect mixins can have with imports. If you have a mixin template which imports a module, then use that template within a class or struct, the import is only considered while inside the mixin template. It is not considered when inside the class or struct. For example:

The previous version would allow the import to be considered where the mixin occurs. In order to have a mixin template add an imported symbol, you can selectively import the symbol. In this case, static import will not work:

Why did we change this?

The explanation seems to be that allowing such imports can create a form of hijacking. Since a class-level import would override a module-level import, a user may not realize that the mixed-in import is present, and therefore overriding a module-level import that is in the local module. The hijacking can come after the fact, in the imported module, without the user’s knowledge or any changes in his code.

Fixing problematic code

There isn’t a very easy way to rectify this problem. The only solution is to selectively import all the symbols you may need from that other module within the mixin.

Transitional Switches

The new version of the compiler comes with two new transitional switches that you can use to find or ignore these errors (note that these affect the mixin template imports as well):

-transition=checkimports: This switch will warn you if you have code that behaved differently prior to issue 10378 being fixed. Note that this may slow down compilation notably, hence it’s not the default2

-transition=import: This switch reverts behavior back to the import rules prior to 10378 being fixed. Only use this switch as a stop-gap measure until you can fix the code!

General Recommendations

Because importing external modules that are outside your control can lead to hijacking, I recommend never importing a module at a scoped level that isn’t selective, static, or renamed. This gives you full control over what invades your namespace. The compiler will protect you now a little bit better, but it’s always better to defend against namespace pollution from an uncontrolled module.

References

D programming language

D Import Spec

Issue 313

Issue 314

Issue 10378

issue 15925

D Compiler Download

  1. Thanks to captaindet for bringing this issue to my attention []
  2. Thanks to Dicebot for pointing this out []