Open Radar

 
Summary:
Trying to implement equality over an Equatable struct with a dictionary of ints to arrays of ints crashes the compiler.


Steps to Reproduce:
1. Attempt to compile this code:

struct A: Equatable {
	var v: [Int: [Int]]
}

func == <T> (left: A, right: A) -> Bool {
	return reduce(map(Set(left.v.keys).union(right.v.keys)) {
			(left.v[$0] ?? []) == (right.v[$0] ?? [])
		}, true) { $0 && $1 }
}



Expected Results:
“Build succeeded”


Actual Results:
S̢҉̴̢͍̤̬͙͔̝̮̳̱̻̪͕͍̱̟́ͅĮ̫̲̯͓̦̥͙̦̝̗̘̝͘͜G̩̤̻̪̤̭͕̠̹̩͚͙͔̀͘ͅS̶̢̳͎̻̗̠̥̖͓͚̼̘̟̟͈̜̗̳̺͍̀E̶̴̴͓̝͈̪̻̠̣̮̣͓̲̘̣̱̳͈̤̝͖͘͜G̛̺̖͓̥̟̦͓̭͎̲͉͘͘V̷̢̻̮̝̩̺̻̟͖̰̮̼̥̼





(Compiler crash in swift::irgen::emitPolymorphicArguments.)

Regression:
It doesn’t crash if you remove the struct’s conformance to Equatable.


Notes:
This is a blocker for me at present and I don’t have a good workaround yet. I am writing this struct at all (vs. using raw dictionaries) because I need the thing to be Equatable, and it can’t be Equatable because Swift can’t express constrained extensions.