Skip to content

Latest commit

 

History

History
35 lines (30 loc) · 2.01 KB

README.md

File metadata and controls

35 lines (30 loc) · 2.01 KB
Raw

Swift Type Inference Bug

This project contains code the reproduces the Swift compiler bug described here. The bug involves the compiler not being able to efficiently perform type inference on semi-simple dictionary/array literals.

I have also written about this issue here, and it has been discussed on Reddit and Hacker News

The only code of interest in this project is in the AppDelegate, which contains the following

// remove employee's in the below literal to speed up compilation time
let myCompany = [
    "employees": [
        "employee 1": ["attribute": "value"],
        "employee 2": ["attribute": "value"],
        "employee 3": ["attribute": "value"],
        "employee 4": ["attribute": "value"],
        "employee 5": ["attribute": "value"],
        "employee 6": ["attribute": "value"],
        "employee 7": ["attribute": "value"],
        "employee 8": ["attribute": "value"],
        "employee 9": ["attribute": "value"],
        "employee 10": ["attribute": "value"],
        "employee 11": ["attribute": "value"],
        "employee 12": ["attribute": "value"],
        "employee 13": ["attribute": "value"],
        "employee 14": ["attribute": "value"],
        "employee 15": ["attribute": "value"],
        "employee 16": ["attribute": "value"],
        "employee 17": ["attribute": "value"],
        "employee 18": ["attribute": "value"],
        "employee 19": ["attribute": "value"],
        "employee 20": ["attribute": "value"]
    ]
]

This code takes a very long time to compile. My estimate is between 12 and 55 hours. The compilation time grows exponentially as each employee is added to the dictionary. Removing employee entries allows the code to build faster.