Tests: Add a typealias test case to lazy_typecheck.swift.

Author: tshortli

test/Inputs/lazy_typecheck.swift

@@ -242,3 +242,7 @@ extension PublicGenericStruct where T == InternalStructForConstraint {}
 
 extension PublicGenericStruct: EmptyPublicProto where T == InternalStructForConstraint {}
 
+// MARK: - Type aliases
+
+public typealias PublicStructAlias = PublicStruct
+typealias InternalTypeAlias = DoesNotExist // expected-error {{cannot find type 'DoesNotExist' in scope}}

test/Inputs/lazy_typecheck_client.swift

@@ -89,3 +89,7 @@ func takesEmptyProto<T: EmptyPublicProto>(_ t: T) {}
 func testConditionalConformance<T>(_ s: PublicGenericStruct<T>) {
   takesEmptyProto(s) // expected-error {{global function 'takesEmptyProto' requires}}
 }
+
+func testTypealiases() {
+  let _: PublicStruct = PublicStructAlias(x: 1)
+}

test/ModuleInterface/lazy-typecheck.swift

@@ -102,6 +102,7 @@
 // CHECK:         public func req() throws -> Swift.Int
 // CHECK:       }
 // CHECK:       #endif
+// CHECK:       public typealias PublicStructAlias = lazy_typecheck.PublicStruct
 // CHECK:       @available(*, unavailable)
 // CHECK-NEXT:  extension lazy_typecheck.PublicGenericStruct : lazy_typecheck.EmptyPublicProto where T : _ConstraintThatIsNotPartOfTheAPIOfThisLibrary {}
 // CHECK:       extension lazy_typecheck.PublicStructIndirectlyConformingToPublicProto : lazy_typecheck.PublicProto {}