Merge pull request #76846 from swiftlang/egorzhdan/std-map-by-literal

[cxx-interop] Conform `std::map` to `ExpressibleByDictionaryLiteral`

Author: egorzhdan

stdlib/public/Cxx/CxxDictionary.swift

@@ -14,9 +14,9 @@
 ///
 /// C++ standard library types such as `std::map` and `std::unordered_map`
 /// conform to this protocol.
-public protocol CxxDictionary<Key, Value> {
-  associatedtype Key
-  associatedtype Value
+public protocol CxxDictionary<Key, Value>: ExpressibleByDictionaryLiteral {
+  override associatedtype Key
+  override associatedtype Value
   associatedtype Element: CxxPair<Key, Value>
   associatedtype RawIterator: UnsafeCxxInputIterator
     where RawIterator.Pointee == Element
@@ -65,6 +65,14 @@ extension CxxDictionary {
     }
   }
 
+  @inlinable
+  public init(dictionaryLiteral elements: (Key, Value)...) {
+    self.init()
+    for (key, value) in elements {
+      self[key] = value
+    }
+  }
+
   @inlinable
   public subscript(key: Key) -> Value? {
     get {

test/Interop/Cxx/stdlib/use-std-map.swift

@@ -71,6 +71,35 @@ StdMapTestSuite.test("MapStrings.init(_: Dictionary<std.string, std.string>)") {
   expectEqual(emptyM.size(), 0)
 }
 
+StdMapTestSuite.test("Map as ExpressibleByDictionaryLiteral") {
+  let m: Map = [-1 : 2, 2 : 3, 33 : 44]
+  expectEqual(m.size(), 3)
+
+  func takesMap(_ m: Map) {
+    expectEqual(m[-1], 2)
+    expectEqual(m[2], 3)
+    expectEqual(m[33], 44)
+  }
+
+  takesMap(m)
+  takesMap([-1 : 2, 2 : 3, 33 : 44])
+}
+
+/// Same as above, but for std::unordered_map.
+StdMapTestSuite.test("UnorderedMap as ExpressibleByDictionaryLiteral") {
+  let m: UnorderedMap = [-1 : 2, 2 : 3, 33 : 44]
+  expectEqual(m.size(), 3)
+
+  func takesUnorderedMap(_ m: UnorderedMap) {
+    expectEqual(m[-1], 2)
+    expectEqual(m[2], 3)
+    expectEqual(m[33], 44)
+  }
+
+  takesUnorderedMap(m)
+  takesUnorderedMap([-1 : 2, 2 : 3, 33 : 44])
+}
+
 StdMapTestSuite.test("Map.subscript") {
   // This relies on the `std::map` conformance to `CxxDictionary` protocol.
   var m = initMap()