[ClangImporter] Preserve the names of imported ObjC properties. (#6182)

This is necessary for proper working of #keyPath, as well as improving
the experience of PrintAsObjC.

rdar://problem/28543037

Author: jrose-apple

lib/ClangImporter/ImportDecl.cpp

@@ -4265,7 +4265,7 @@ namespace {
       // Turn this into a computed property.
       // FIXME: Fake locations for '{' and '}'?
       result->makeComputed(SourceLoc(), getter, setter, nullptr, SourceLoc());
-      addObjCAttribute(result, None);
+      addObjCAttribute(result, Impl.importIdentifier(decl->getIdentifier()));
       applyPropertyOwnership(result, decl->getPropertyAttributesAsWritten());
 
       // Handle attributes.

test/PrintAsObjC/Inputs/custom-modules/override.h

@@ -6,6 +6,7 @@
 - (NSUInteger)foo:(NSUInteger)x y:(NSUInteger)y;
 
 @property(readonly,getter=getProp) NSUInteger prop;
+@property(readonly) NSInteger originalName __attribute__((swift_name("renamedProp")));
 
 - (id)objectAtIndexedSubscript:(NSUInteger)idx;
 

test/PrintAsObjC/override.swift

@@ -23,6 +23,8 @@ import OverrideBase
 class A_Child : Base {
   // CHECK-NEXT: @property (nonatomic, readonly, getter=getProp) NSUInteger prop;
   override var prop: Int { return 0 }
+  // CHECK-NEXT: @property (nonatomic, readonly) NSInteger originalName;
+  override var renamedProp: Int { return 0 }
   // CHECK-NEXT: - (id _Nullable)objectAtIndexedSubscript:(NSUInteger)x SWIFT_WARN_UNUSED_RESULT;
   override subscript(x: Int) -> Any? { return nil }
 

test/SILGen/Inputs/usr/include/Gizmo.h

@@ -65,6 +65,8 @@ typedef long NSInteger;
 + (Gizmo*)nonNilGizmo __attribute__((swift_name("nonNilGizmo()")));
 @property Gizmo* nonNilGizmoProperty;
 @property (unsafe_unretained) Gizmo* unownedNonNilGizmoProperty;
+
+@property id originalName __attribute__((swift_name("renamedProp")));
 @end
 
 @interface Guisemeau : Gizmo

test/SILGen/objc_keypath.swift

@@ -4,6 +4,7 @@
 
 import ObjectiveC
 import Foundation
+import gizmo
 
 @objc class Foo : NSObject {
   @objc(firstProp) var fooProp: Foo?
@@ -14,4 +15,10 @@ import Foundation
 func createKeyPath() -> String {
   // CHECK: string_literal utf8 "firstProp.secondProp"
   return #keyPath(Foo.fooProp.stringProp)
-}
+} // CHECK: } // end sil function '_TF12objc_keypath13createKeyPathFT_SS'
+
+// CHECK-LABEL: sil hidden @_TF12objc_keypath21createKeyPathImportedFT_SS
+func createKeyPathImported() -> String {
+  // CHECK: string_literal utf8 "originalName"
+  return #keyPath(Gizmo.renamedProp)
+} // CHECK: } // end sil function '_TF12objc_keypath21createKeyPathImportedFT_SS'