Fix crash checking objcImpl block property

lib/Sema/TypeCheckDeclObjC.cpp

@@ -3283,17 +3283,25 @@ class ObjCImplementationChecker {
           if (reqParams.size() != implParams.size())
             return false;
 
-          auto implParamList =
-              cast<AbstractFunctionDecl>(implDecl)->getParameters();
+          ParameterList *implParamList = nullptr;
+          if (auto afd = dyn_cast<AbstractFunctionDecl>(implDecl))
+            implParamList = afd->getParameters();
 
           for (auto i : indices(reqParams)) {
             const auto &reqParam = reqParams[i];
             const auto &implParam = implParams[i];
-            ParamDecl *implParamDecl = implParamList->get(i);
-
-            if (!matchParamTypes(reqParam.getOldType(), implParam.getOldType(),
-                                 implParamDecl))
-              return false;
+            if (implParamList) {
+              // Some of the parameters may be IUOs; apply special logic.
+              if (!matchParamTypes(reqParam.getOldType(),
+                                   implParam.getOldType(),
+                                   implParamList->get(i)))
+                return false;
+            } else {
+              // IUOs not allowed here; apply ordinary logic.
+              if (!reqParam.getOldType()->matchesParameter(
+                      implParam.getOldType(), matchOpts))
+                return false;
+            }
           }
 
           return matchTypes(funcReqTy->getResult(), funcImplTy->getResult(),

test/decl/ext/Inputs/objc_implementation.h

@@ -57,6 +57,9 @@
 - (void)instanceMethod1:(int)param;
 - (void)instanceMethod2:(int)param;
 
+// rdar://122280735 - crash when the parameter of a block property needs @escaping
+@property (nonatomic, readonly) void (^ _Nonnull rdar122280735)(void (^_Nonnull completion)());
+
 @end
 
 @interface ObjCClass () <NSCopying>

test/decl/ext/objc_implementation.swift

@@ -225,6 +225,10 @@ protocol EmptySwiftProto {}
     // OK
     return self
   }
+
+  // rdar://122280735 - crash when the parameter of a block property needs @escaping
+  let rdar122280735: (() -> ()) -> Void = { _ in }
+  // expected-warning@-1 {{property 'rdar122280735' of type '(() -> ()) -> Void' does not match type '(@escaping () -> Void) -> Void' declared by the header}}
 }
 
 @_objcImplementation(PresentAdditions) extension ObjCClass {

test/decl/ext/objc_implementation_conflicts.swift

@@ -175,6 +175,8 @@ import objc_implementation_private
   @objc func extensionMethod(fromHeader2: CInt) {}
 
   @objc(copyWithZone:) func copy(with zone: NSZone?) -> Any { self }
+
+  let rdar122280735: (@escaping () -> ()) -> Void = { _ in }
 }
 
 @_objcImplementation(PresentAdditions) extension ObjCClass {