Tests: Add a MemberImportVisibility test case for rdar://162130647.

Author: tshortli

test/NameLookup/Inputs/MemberImportVisibility/members_A.swift

@@ -79,3 +79,9 @@ public protocol ProtocolInA {
 extension ProtocolInA {
   public func defaultedRequirementInA() { }
 }
+
+public struct EquatableInA: Equatable {
+  public static func ==(_: Self, _: Self) -> Bool {
+    false
+  }
+}

test/NameLookup/Inputs/MemberImportVisibility/members_B.swift

@@ -59,3 +59,9 @@ open class DerivedClassInB: BaseClassInA {
 extension ProtocolInA {
   public func defaultedRequirementInB() { }
 }
+
+public struct EquatableInB: Equatable {
+  public static func ==(_: EquatableInB, _: EquatableInB) -> Bool {
+    false
+  }
+}

test/NameLookup/Inputs/MemberImportVisibility/members_C.swift

@@ -52,3 +52,15 @@ open class DerivedClassInC: DerivedClassInB {
 extension ProtocolInA {
   public func defaultedRequirementInC() { }
 }
+
+public struct EquatableInC: Equatable {
+  public static func ==(_: EquatableInC, _: EquatableInC) -> Bool {
+    false
+  }
+}
+
+public struct HasEquatableMembers {
+  public var a: EquatableInA
+  public var b: EquatableInB
+  public var c: EquatableInC
+}

test/NameLookup/member_import_visibility.swift

@@ -167,3 +167,14 @@ func testLeadingDotSyntax() {
   takesP(.zInC)
   takesP(.zAmbiguous)
 }
+
+func testConformanceMember(_ h1: HasEquatableMembers, _ h2: HasEquatableMembers) {
+  _ = h1.a == h2.a
+  // Technically, this references the EquatableInB.== member that hasn't been
+  // imported. However, the conformance of EquatableInB: Equatable is visible
+  // here because conformances are not yet subject to import visibility rules.
+  // As a result, the == requirement is technically visible and therefore there
+  // should be no diagnostic with MemberImportVisibility enabled.
+  _ = h1.b == h2.b
+  _ = h1.c == h2.c
+}