[Frontend] Always output (some) additional files when allowing errors

lib/AST/Decl.cpp

@@ -6808,8 +6808,8 @@ const ParamDecl *swift::getParameterAt(const ValueDecl *source,
 Type AbstractFunctionDecl::getMethodInterfaceType() const {
   assert(getDeclContext()->isTypeContext());
   auto Ty = getInterfaceType();
-  if (Ty->hasError())
-    return ErrorType::get(getASTContext());
+  if (Ty->is<ErrorType>())
+    return Ty;
   return Ty->castTo<AnyFunctionType>()->getResult();
 }
 

lib/FrontendTool/FrontendTool.cpp

@@ -640,7 +640,10 @@ static void emitSwiftdepsForAllPrimaryInputsIfNeeded(
   //
   // FIXME: It seems more appropriate for the driver to notice the early-exit
   // and react by always enqueuing the jobs it dropped in the other waves.
-  if (Instance.getDiags().hadAnyError())
+  //
+  // We will output a module if allowing errors, so ignore that case.
+  if (Instance.getDiags().hadAnyError() &&
+      !Invocation.getFrontendOptions().AllowModuleWithCompilerErrors)
     return;
 
   for (auto *SF : Instance.getPrimarySourceFiles()) {
@@ -989,11 +992,12 @@ static void performEndOfPipelineActions(CompilerInstance &Instance) {
   if (!ctx.hadError()) {
     emitLoadedModuleTraceForAllPrimariesIfNeeded(
         Instance.getMainModule(), Instance.getDependencyTracker(), opts);
-
-    emitAnyWholeModulePostTypeCheckSupplementaryOutputs(Instance);
 
     dumpAPIIfNeeded(Instance);
   }
+  if (!ctx.hadError() || opts.AllowModuleWithCompilerErrors) {
+    emitAnyWholeModulePostTypeCheckSupplementaryOutputs(Instance);
+  }
 
   // Verify reference dependencies of the current compilation job. Note this
   // must be run *before* verifying diagnostics so that the former can be tested

lib/PrintAsObjC/DeclAndTypePrinter.cpp

@@ -1597,6 +1597,10 @@ class DeclAndTypePrinter::Implementation
     os << " */";
   }
 
+  void visitErrorType(ErrorType *Ty, Optional<OptionalTypeKind> optionalKind) {
+    os << "/* error */id";
+  }
+
   bool isClangPointerType(const clang::TypeDecl *clangTypeDecl) const {
     ASTContext &ctx = getASTContext();
     auto &clangASTContext = ctx.getClangModuleLoader()->getClangASTContext();

test/Frontend/allow-errors.swift

@@ -1,9 +1,12 @@
 // RUN: %empty-directory(%t)
 
 // The module should be generated regardless of errors and diagnostic should still be output
-// RUN: %target-swift-frontend -verify -emit-module -o %t/errors.swiftmodule -experimental-allow-module-with-compiler-errors -D ERROR_MODULE %s
+// RUN: %target-swift-frontend -verify -emit-module -o %t/errors.swiftmodule -emit-reference-dependencies-path %t/errors.swiftdeps -emit-dependencies-path %t/errors.d -experimental-allow-module-with-compiler-errors -D ERROR_MODULE -primary-file %s
 // RUN: llvm-bcanalyzer %t/errors.swiftmodule | %FileCheck -check-prefix=CHECK-BC %s
 // CHECK-BC-NOT: UnknownCode
+// RUN: ls %t/errors.swiftdeps
+// RUN: ls %t/errors.d
+
 #if ERROR_MODULE
 public struct ValidStructInvalidMember {
   public var member: String

test/PrintAsObjC/error.swift

@@ -0,0 +1,60 @@
+// RUN: %empty-directory(%t)
+// RdsagUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) %s -typecheck -emit-objc-header-path %t/error.h
+// RUadsgN: %FileCheck %s < %t/error.h
+
+// 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: %check-in-clang %t/error.h
+
+// REQUIRES: objc_interop
+
+import Foundation
+
+@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
+
+  @objc func method() {}
+  // CHECK: - (void)method;
+
+  @objc func methodParams(a: Int, b: Int) {}
+  // CHECK: - (void)methodParamsWithA:(NSInteger)a b:(NSInteger)b;
+
+  @objc class func classMethod() {}
+  // CHECK: + (void)classMethod;
+
+  @objc(objcMethod)
+  func renamedMethod() {}
+  // CHECK: - (void)objcMethod;
+
+  @objc func invalidBody() {
+  // CHECK: - (void)invalidBody;
+    undefined
+  }
+
+  @objc func invalidRet() -> undefined {}
+  // CHECK: - (/* error */id)invalidRet
+
+  @objc func invalidParams(a: undefined) {}
+  // TODO: Not output with invalid parameters
+
+  @objc(invalid::)
+  func invalidRenamedMethod() {}
+  // CHECK: - (void)invalidRenamedMethod;
+
+  @objc @undefined func invalidAttribute() {}
+  // CHECK: - (void)invalidAttribute;
+
+  @objc undefined func invalidModifier() {}
+  // TODO: Not output with invalid modifier
+
+  @objc @available
+  func invalidAvailability() {}
+  // CHECK: - (void)invalidAvailability;
+}
+
+@objc class InvalidParent: undefined {}
+// CHECK: @interface InvalidParent