JSONEncoder / Encodable: Floating point rounding error

Using Swift
36
But wait, am I still confused or does it actually have to do with SR-12312 after all?

On my machine (without the bug fix (despite having the latest Xcode (see comments in SR-12312))):

$ swiftc --version
Apple Swift version 5.3 (swiftlang-1200.0.29.2 clang-1200.0.30.1)
Target: x86_64-apple-darwin19.6.0 <---

I'll see this:

let someFloat = 7.038531e-26 as Float
print(someFloat == Float(Double(String(someFloat))!))
// Prints false <---
print(someFloat == Float._convert(from: Double(String(someFloat))!).value)
// Prints true <---

(Those should both print true if SR-12312 is fixed, shouldn't they? Ie, there is generics involved, behind the scenes.)

But (and now I'm guessing) on eg @xwu's machine (with the bug fix):

$ swiftc --version
Apple Swift version 5.3 (swiftlang-1200.0.29.2 clang-1200.0.30.1)
Target: x86_64-apple-darwin20.1.0 <---

I think they'll see this:

let someFloat = 7.038531e-26 as Float
print(someFloat == Float(Double(String(someFloat))!))
// Prints true <---
print(someFloat == Float._convert(from: Double(String(someFloat))!).value)
// Prints true

Would you mind checking this @xwu?