[SR-6910] Swift 4.1: Dictionary<HashableType1, HashableType2> is not Hashable

[NachoSoto]

Previous ID	SR-6910
Radar	rdar://problem/38970262
Original Reporter	@NachoSoto
Type	Bug
Status	Resolved
Resolution	Done

Environment

Swift version 4.1 (swiftlang-902.0.34 clang-902.0.30)

Additional Detail from JIRA

Votes	0
Component/s	Compiler, Standard Library
Labels	Bug
Assignee	@lorentey
Priority	Medium

md5: 90d47260fa73af573e9d156feeab6a94

Issue Description:

Because of SR-6801, I spent an hour trying to understand why my type would not get automatic synthesis of Hashable. I narrowed it down to this:

func f<T: Hashable>(_ t: T) {}
let a: [String: String] = [:]

f(a)

Equatable.swift:4:3: error: argument type '[String : String]' does not conform to expected type 'Hashable'
f(a)
  ^

[NachoSoto]

Oooh @jckarter points out that this is still WIP: #14247

[lorentey]

@swift-ci create

[lorentey]

SE-0143 has been amended to explicitly allow Hashable conformances for Optional, Array, ContiguousArray, ArraySlice, Dictionary, Range, and ClosedRange.

We've implemented these changes in PR #15382; it has now landed on the master branch.