[PrintAsObjC] Do not output invalid decls when allowing errors

We still want the ObjectiveC header when allowing errors, but make sure
to skip printing out any invalid declarations that may be caused because
of those errors.

In particular, duplicate declarations were causing a crash when sorting
declarations where various assumptions would end up casting a
non-ExtensionDecl to an ExtensionDecl.

Resolves rdar://78023656

Author: bnbarham

lib/PrintAsObjC/DeclAndTypePrinter.cpp

@@ -2017,7 +2017,7 @@ auto DeclAndTypePrinter::getImpl() -> Implementation {
 }
 
 bool DeclAndTypePrinter::shouldInclude(const ValueDecl *VD) {
-  return isVisibleToObjC(VD, minRequiredAccess) &&
+  return !VD->isInvalid() && isVisibleToObjC(VD, minRequiredAccess) &&
          !VD->getAttrs().hasAttribute<ImplementationOnlyAttr>();
 }
 

test/PrintAsObjC/error.swift

@@ -1,18 +1,23 @@
 // RUN: %empty-directory(%t)
 // RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -emit-module-path %t/error.swiftmodule -emit-objc-header-path %t/error.h -experimental-allow-module-with-compiler-errors %s
-// RUN: %FileCheck %s < %t/error.h
+// RUN: %FileCheck --input-file %t/error.h %s
 // RUN: %check-in-clang %t/error.h
 
 // REQUIRES: objc_interop
 
 import Foundation
 
+// TODO: Ideally we'd output invalid decls regardless (so that they could eg. be used in code
+// completion), but we avoid doing so for now to prevent crashes. Revisit later to handle a possibly
+// invalid AST while printing the ObjectiveC header.
+
 @objc class ErrorClass: NSObject {
 // CHECK: @interface ErrorClass
   @objc let member: Int
   // CHECK: @property {{.*}} NSInteger member;
+
   @objc let invalidMember: undefined
-  // TODO: Not output on invalid type
+  // TODO: Missing
 
   @objc func method() {}
   // CHECK: - (void)method;
@@ -33,10 +38,10 @@ import Foundation
   }
 
   @objc func invalidRet() -> undefined {}
-  // CHECK: - (/* error */id)invalidRet
+  // TODO: Missing
 
   @objc func invalidParams(a: undefined) {}
-  // TODO: Not output with invalid parameters
+  // TODO: Missing
 
   @objc(invalid::)
   func invalidRenamedMethod() {}
@@ -55,3 +60,6 @@ import Foundation
 
 @objc class InvalidParent: undefined {}
 // CHECK: @interface InvalidParent
+
+// Used to crash during sorting due to assumptions regarding the Decl kind
+@objc class ErrorClass: NSObject {}