https://github.com/protonull/bonkersvarargscompiletest

Turns out, type inference in varargs is REALLY BAD
https://github.com/protonull/bonkersvarargscompiletest

Last synced: 27 days ago
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Turns out, type inference in varargs is REALLY BAD

• Host: GitHub
• URL: https://github.com/protonull/bonkersvarargscompiletest
• Owner: Protonull
• License: gpl-3.0
• Created: 2023-11-25T11:00:26.000Z (about 1 year ago)
• Default Branch: master
• Last Pushed: 2023-11-27T18:55:46.000Z (about 1 year ago)
• Last Synced: 2024-04-24T07:44:05.757Z (8 months ago)
• Language: Java
• Size: 32.2 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# BonkersVarargsCompileTest

Came across this issue while working on a project fork. There was a class with

ostensibly static data, but were just exposed HashMaps and HashSets, so I used

Java's Map and Set [ofEntries() methods](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/Map.html#ofEntries%28java.util.Map.Entry...%29) 

that were added in Java 9, but this turned out to increase compilation from

around 10 seconds to around 11 minutes, a 66x increase.

After some asking around and testing, we narrowed it down to vararg type

inference.

- **ColourConstantsVarargs.java:** This is a direct copy-paste of my edit that

  ruined my life for two hours.

- **ColourConstantsPremadeVarargs.java:** This was a hacky test to determine

  whether the auto-generated varargs-array was the problem. (It was.)

- **ColourConstantsCopyOf.java:** This is what the class looked like before my

  edit, except I've wrapped it in a Map.copyOf() just to see whether there's

  some issue with Map APIs.

- **ColourConstantsTypedVarargs.java:** This was to test whether removing type

  inference by making it explicit removes the problem. (It does.)

There's something in particular about type-inference within an auto-generated

varargs array that the compiler just does not like, and causes compilation time

to massively suffer.

## How to run

Clone this repo and execute `sh run.sh`

## Results

```

openjdk 17.0.9 2023-10-17 LTS

OpenJDK Runtime Environment Corretto-17.0.9.8.1 (build 17.0.9+8-LTS)

OpenJDK 64-Bit Server VM Corretto-17.0.9.8.1 (build 17.0.9+8-LTS, mixed mode, sharing)

Compiling Varargs

Time: 4:52.91

Compiling Premade Varargs

Time: 0:00.65

Compiling Copy Of

Time: 0:00.53

Compiling Typed Varargs

Time: 0:00.60

```

How did you do?