Jared Parsons
@jaredpar
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Work on compilers and languages. Creator of VsVim. He/Him #BlackLivesMatter
Redmond, WA
Joined December 2008
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I'm the C# compiler lead and at least twice a week I forget whether 'class' must come first or last in a constraint clause.
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Step 1: buy cake
Step 2: send email saying “cake in room ...”
Step 3: “now that you’re all here let’s talk about our build files”
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Confession: I've worked on the C# team for ~10 years now and I still have to look up array creation syntax on a semi-regular basis.
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Old Hotness: !string.IsNullOrEmpty(x)
New Hotness: x is { Length: > 0}
C# 9.0 FTW
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.NET exception advice:
Q: What should I throw?
A: System.Exception
Q: What should I catch?
A: System.Exception
The .NET exception model is a Pokémon based system. Gotta catch them all.
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Levels of software ownership:
1. Actively developed
2. Maintained
3. Servicing only
4. Last one who touched it owns it
5. Last one who looked at it owns it
6. Pray nothing needs fixing
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Today marks 17 years at Microsoft. In that time:
- 12 different bosses
- ~11 different offices
- 4 different product groups
- Countless friends made along the way
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My coworkers decided to turn on captions for my Span<T> talk. Turns out they use automated translation for that. The result: Manatee Memory
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C# compiler now a pure .NET Core application inside the .NET SDK. Before our DLLs, where all compiler logic lives, were netstandard2.0 with a tiny netcoreapp3.1 exe on top. Now it's netcoreapp3.1 through and through.
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Developer fallacy: we're going to rewrite this established product from scratch and fix all the bugs in the current implementation. It will be awesome!
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The .NET Community Stand up was fun today. Got to show viewers the evolution of code that leads us to the following being legal
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Think developers should embrace `is object` as the canonical non-null test in C#. It works in every version, won't compile when the expression type is a struct, logical opposite of `is null`, emits efficient IL, ... the only fault you can say is the name isn't obvious.
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Law of Microsoft: never stop a meeting organizer who's trying to end a meeting early
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The most under appreciated part of Visual Studio over the last three major releases is the Installer. I comfortably run and manage 3-5 versions of Visual Studio with different configurations on most of my boxes. Upgrades, installs and uninstalls are so smooth.
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Removed some truly ancient code from roslyn today (code targeting .NET Framework 2.0). The change had no push back, every test passed, test insertions into VS passed ... green all across the board.
I could not be more terrified.
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Career advice for younger developers: make sure always spend part of your time becoming a better writer. Code is only going to take you so far. At some point you need to be able to effectively communicate your ideas with other people.
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Just hit my 20 year anniversary at Microsoft. It's pretty daunting to look back at all the products and features I've worked on over the years and where they are now. The good news though is I'm still having fun ;)
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Me as a junior dev: why don't people trust me more and believe in my designs?
Me as a senior dev: why on earth do these people trust me and my designs? Haven't they seen the mistakes I've made before?
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Committing a C# coding sin today: putting more than one type in a single file.
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In case you are feeling evil this is potentially legal C# code
public class C {
async async await(await async) => await async;
}
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"The best thing about UDP jokes is that I don’t care if you get them or not."
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Every thing you teach your kids will come back to haunt you. Recently got an egg timer so my toddler can visualize what "5 more minutes" looks like. Today I said "5 more min and I'll be done". He said okay, walked over to the egg timer, set it for 5 minutes and said "only 5 min"
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Today's evil creation:
class await {
async async async(async async) => await async(async(async));
}
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C# language design is
10% exploring cool ideas
75% overload resolution
15% being sad at past decisions we made
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Wanted to share the steps I use when attempting to establish a coding style in a software project. Seen a number of people struggle with this over the years and wanted to share a strategy I've had some success with.
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Reminder that dotnet/runtime is now open for contribution. This will be the repository for the .NET 5 runtime.
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The design proposal for init properties in C# 9 is up on csharplang now.
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After a year of previews and betas, time to get that sweet sweet RTM install of .NET 5
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Absolutely terrible advice. The proper advice here is stop adding comments about "what" but keep adding comments about "why". Code tells you what it does, the comments tell you why that was necessary
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I think developers often lose sight of the fact that the C# type system is not the .NET type system. Instead the C# type system is merely a layer on top of the .NET type system providing both additional capabilities and additional restrictions.
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This aged well
Tweet why you’re leaving Netflix. The top three most creative tweets using
#GoodbyeNetflix
will win a 1-year subscription to Blockbuster!
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Good: After an hour of debugging finally figured out my tests weren't hanging instead the virus checker was blocking them from running.
Bad: Found this out during a meeting when I was unmuted and chose to tell the virus checker how I felt about the wasted time.
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C# pattern matching making for some really nice changes in the compiler
if (member is IMethodSymbol
{
DeclaredAccessibility: Accessibility.Public,
IsStatic: false,
Parameters: { Length: 0 },
Arity: 0
} method)
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After some consideration decided we should make semicolons optional in C#
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Got a core dump for a .NET 5 process running on Linux today. Opened it in Visual Studio, attached the debugger and it just worked. Zero friction. Basically magic.
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Don’t understand why so many of my coworkers have an uncountable number of tabs open in the browser. How do you find anything useful with that setup? After 10 tabs I just get annoyed and start closing things.
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Blog: why C# 11 is issuing warnings about lower case type names
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When C# local function shipped pretty much immediately got a bug report where a user had a 10,000 line program with only a Main method and ~50 local functions inside it. At the time I thought "okay ... but why???". Now though I must confess: I am that user.
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ref struct can now implement interfaces and participate in generics. Excited to see all of the ways the community finds to use this
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The more I WFH the more I think I need two keyboards:
1. Mechanical keyboard for coding and email
2. Quiet keyboard for stealth typing in Teams meetings
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Span<T> work now merged into the C# master branch. Next stop is the 7.2 release!
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Another developer converted to "x is object" as the canonical null check in C#. If I have to go dev by dev to achieve correctness then so be it.
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Junior Dev: Really excited cause my change passed CI on first try.
Senior Dev: Really worried cause my change passed CI on first try.
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Me 5 years ago: Dad you really google facebook to get to ?
Me yesterday: google "azure portal", click, login OMG I'M MY FATHER
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Me: tall strawberry refresher
Starbucks: with or without lemonade
Me: ... i'm just gonna be honest, my wife did not prepare me to answer that question.
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When’s the last time you emailed a junior coworker and told them: hey that was really well written email, nice PR for a weird bug, great issue write up, etc ...?
I got a few of these when I was a junior dev. Meant the world to me and my confidence.
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Really excited about what's happening our low level hackathon this year ...
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This PR is essentially a farewell to Jenkins. It's been our CI system since we originally went OSS on GitHub. This PR though completes the transition of dotnet/roslyn to
@AzureDevOps
.
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These days I start most PR reviews by looking at the tests first. If that doesn't tell me what the change is doing then I've found the first problem.
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Long time coming but in C# 11 method group to delegate conversions will be cached just as lambdas are today
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Now that C# supports module initializers, the ability to run code when your library is loaded, how do you plan on abusing them ... I mean using them in your apps?
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What type of talks would you like to see from the .NET Compilers / Language design team?
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In dotnet/runtime a test runs on average 50 times in CI. There about 100 CI / PR builds a day. That means a given test runs on about 25,000 times in a work week. At that scale a test passing 99.99% of the time isn't good enough
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The biggest problem with ITestOutputHelper in xUnit is that most developers don't know about it and how much value it can add to tests.
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We're very nearly at the finish line now for C# 9 and earlier this week I was asked essentially: what has surprised you the most with C# 9 so far in terms of how customers have received it?
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Can't remember the last time I defined or used an event in C#.
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Windows Key + Shift + S. This will change your life if you ever do screen captures.
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This is why I start all my C# programs with ManyFiles.cs. That way even though I put all my code in one file I can confidently tell people "All my code is not in a SingleFile, it's in ManyFiles"
"If we have minimal APIs, everything will end up in a single file".
Me: Don't put everything in a single file......
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The irony of a change for the C# nullable reference types feature introducing a null reference exception into the compiler.
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@bradwilson
@maoni0
@jonskeet
When
@jonskeet
sends a "found a bug" email then it's a bug. When he sends a "can you help me understand why this is happening" email then it's a panic attack.
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Wife: about to start a meeting
Me: can I eat down here?
Wife: yes, just don’t be too loud
Me: how loud is too loud
Wife: you should leave
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C# feature just merged for preview 4: ability to have arbitrary Task-like returns in async methods. In other words: async ValueTask<T> Go()
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Question: Do u love or hate COM?
Answer when thinking about COM: it's a really elegant spec that is so complete and well thought out.
Answer when working on a COM bug: this is the devil incarnate
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Remote presenting is just like in person presenting. When I tell jokes I can only hear myself laughing.
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Deleting this ancient type of code must break something. Everything about my experience as a dev tells me this is true.
So now I've broken something and I have no idea what it is.
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@kateward
Microsoft is a company you can have multiple different careers at. It's a big company, if you feel stale in one area there are lots of opportunities to shift to another very different area but still maintain all the social connections you had before.
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C# work on default interfaces officially begins
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Initial proposal for allowing ref fields in C# is available for review. This also covers structs returning ref to their fields as well as safe fixed sized buffers
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New first. Texting my wife’s coworker to get her to send my wife a teams message to come unlock the back door so I can get back into the house. Why not text my wife? Cause she left her phone outside next to me.
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C# 8.0 default interface methods now passing on Mono as well as CoreClr.
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Module initailizers are merging into C# 9 main branch. Try not to abuse them ... too much ;)
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Also helps if you take the seat nearest the door to prevent rapid escape attempts
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The dotnet/roslyn repository now has nullability checks on by default. Just merged the PR that flipped the default for us and simultaneously changed ~10,000 files to keep the current semantics the same.
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Just spent an embarrassingly long amount of time searching for the VS 2022 installation on my hard drive before I realized I was searching in "Program Files (x86)" and not "Program Files". Going to take my brain a few years to adjust to this new world :)
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Code review tip: review tests first. If you can't tell from the test changes alone what is being fixed then it's a sign there aren't enough tests.
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It's common for members of the C# compiler team, even those with 10+ years experience, to learn new things about the language. It's a bit rarer when the new thing surprises the entire team room.
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@mkristensen
This is what the C# compiler team uses to troll the C# IDE team with perf issues.
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Time to sit down and finish my proposal for init only fields and properties for tomorrow's C# LDM. This should make it easier to declare and consume immutable data in C#.
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The answer to "is this thread safe?" is either a) no or b) it's immutable. Any other answer lacks necessary context and is at best a guess
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Today as I return from parental leave I'm reflecting on just how awesome this benefit is at
@microsoft
. For the last eight weeks I've been at home bonding with my daughter, watching her grow, eat and become aware of her world.
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<jaredpar enters .NET API design />
Should we use SecureString there?
<jaredpar was removed from .NET API design />
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Q: who owns this test?
A: send a PR to delete the test. The person who blocks the PR is the owner.
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One of my really simple but really satisfying uses of pattern matching
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"I'm just gonna let my hair grow until this COVID thing is over". That was a really fun thought four months ago but now it's getting problematic.
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The change to make Roslyn target netstandard2.0 is now merged
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Tend to jump around between VS and VS Code and one of the more frustrating gaps is being able to type "code ." but not "devenv ."
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