Regarding Swift type inference compile-time performance

Using Swift
3

We can measure it. :slight_smile:

I've multiplied it by a 1000 to get a better signal.

Benchmark #1: xcrun swiftc -typecheck a.swift
  Time (mean ± σ):     175.7 ms ±   3.5 ms    [User: 82.9 ms, System: 81.9 ms]
  Range (min … max):   171.0 ms … 182.8 ms    16 runs

Benchmark #1: xcrun swiftc -typecheck b.swift
  Time (mean ± σ):     224.8 ms ±   2.8 ms    [User: 131.1 ms, System: 81.7 ms]
  Range (min … max):   220.2 ms … 228.2 ms    13 runs

Benchmark #1: xcrun swiftc -typecheck c.swift
  Time (mean ± σ):     672.3 ms ±   8.0 ms    [User: 568.3 ms, System: 93.7 ms]
  Range (min … max):   662.4 ms … 685.1 ms    10 runs

Benchmark #1: xcrun swiftc -typecheck d.swift
  Time (mean ± σ):     213.3 ms ±   2.0 ms    [User: 119.8 ms, System: 81.6 ms]
  Range (min … max):   210.2 ms … 216.5 ms    13 runs

Here's the test script using the hyperfine utility.

#!/usr/bin/env python3
import os

filenames = ["a", "b", "c", "d"]
code = [
  'let a{} = "hello, world!"',
  'let b{} = String("hello, world!")',
  'let c{}: String = .init("hello, world!")',
  'let d{}: String = "hello, world!"'
]

for (i, filename) in enumerate(filenames):
    with open(filename + ".swift", "w") as f:
        s = ""
        for j in range(1000):
            s += (code[i] + '\n').format(j)
        f.write(s)
    os.system("hyperfine 'xcrun swiftc -typecheck {}'".format(filename + ".swift"))
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