Stub fix-its for missing objcImpl requirements

Changes the diagnostics emitted when an `@objc @implementation` extension is missing some of the members required by the extension:

• We now emit one error on the extension, plus a note for each missing member.
• Where possible, the notes have a fix-it adding a stub.

For example:

```
  9 | @objc @implementation extension ObjCClass {
    |                       |- error: extension for main class interface does not provide all required implementations
    |                       |- note: missing instance method 'method(fromHeader3:)'
    |                       |- note: missing instance method 'method(fromHeader4:)'
    |                       |- note: missing property 'propertyFromHeader7'
    |                       |- note: missing property 'propertyFromHeader8'
    |                       |- note: missing property 'propertyFromHeader9'
    |                       |- note: missing instance method 'extensionMethod(fromHeader2:)'
    |                       `- note: add stubs for missing '@implementation' requirements
```

With a fix-it on the last note to insert the following after the open brace:

```

  @objc(methodFromHeader3:)
  open func method(fromHeader3 param: Int32) {
      <#code#>
  }

  @objc(methodFromHeader4:)
  open func method(fromHeader4 param: Int32) {
      <#code#>
  }

  @objc(propertyFromHeader7)
  open var propertyFromHeader7: Int32 {
      get {
          <#code#>
      }
      set(propertyFromHeader7) {
          <#code#>
      }
  }

  @objc(propertyFromHeader8)
  open var propertyFromHeader8: Int32 {
      get {
          <#code#>
      }
      set(propertyFromHeader8) {
          <#code#>
      }
  }

  @objc(propertyFromHeader9)
  open var propertyFromHeader9: Int32 {
      get {
          <#code#>
      }
      set(propertyFromHeader9) {
          <#code#>
      }
  }

  @objc(extensionMethodFromHeader2:)
  open func extensionMethod(fromHeader2 param: Int32) {
      <#code#>
  }

```

Fixes rdar://130038221.

Author: beccadax

include/swift/AST/ASTPrinter.h

@@ -413,7 +413,8 @@ class ExtraIndentStreamPrinter : public StreamPrinter {
 void printContext(raw_ostream &os, DeclContext *dc);
 
 bool printRequirementStub(ValueDecl *Requirement, DeclContext *Adopter,
-                          Type AdopterTy, SourceLoc TypeLoc, raw_ostream &OS);
+                          Type AdopterTy, SourceLoc TypeLoc, raw_ostream &OS,
+                          bool withExplicitObjCAttr = false);
 
 /// Print a keyword or punctuator directly by its kind.
 llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, tok keyword);

include/swift/AST/DiagnosticsSema.def

@@ -1976,10 +1976,16 @@ ERROR(objc_implementation_wrong_swift_name,none,
       "you mean %1?",
       (ObjCSelector, const ValueDecl *))
 
-ERROR(objc_implementation_missing_impl,none,
-      "extension for %select{main class interface|category %0}0 should "
-      "provide implementation for %kind1",
-      (Identifier, ValueDecl *))
+ERROR(objc_implementation_missing_impls,none,
+      "extension for %select{main class interface|category %0}0 does not "
+      "provide all required implementations",
+      (Identifier))
+NOTE(objc_implementation_missing_impls_fixit,none,
+     "add stub%s0 for missing '@implementation' requirement%s0",
+     (unsigned))
+NOTE(objc_implementation_missing_impl,none,
+     "missing %kind0",
+     (ValueDecl *))
 
 ERROR(objc_implementation_class_or_instance_mismatch,none,
       "%kind0 does not match %1 declared in header",

lib/Sema/TypeCheckDeclObjC.cpp

@@ -19,6 +19,7 @@
 #include "TypeCheckProtocol.h"
 #include "TypeChecker.h"
 #include "swift/AST/ASTContext.h"
+#include "swift/AST/ASTPrinter.h"
 #include "swift/AST/AvailabilityInference.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/ExistentialLayout.h"
@@ -4048,18 +4049,38 @@ class ObjCImplementationChecker {
 
 public:
   void diagnoseUnmatchedRequirements() {
+    auto ext = dyn_cast<ExtensionDecl>(decl);
+    if (!ext)
+      return;
+
+    llvm::SmallString<128> stubs;
+    llvm::raw_svector_ostream stubStream(stubs);
+
+    unsigned numEmitted = 0;
+
     for (auto req : unmatchedRequirements) {
       // Ignore `@optional` protocol requirements.
       if (isOptionalObjCProtocolRequirement(req))
         continue;
 
-      auto ext = cast<IterableDeclContext>(req->getDeclContext()->getAsDecl())
-                        ->getImplementationContext();
+      if (numEmitted == 0) {
+        // Emit overall diagnostic for all the notes to attach to.
+        diagnose(ext, diag::objc_implementation_missing_impls,
+                 getCategoryName(req->getDeclContext()));
+      }
+
+      numEmitted += 1;
+      diagnose(ext, diag::objc_implementation_missing_impl, req);
 
-      diagnose(ext->getDecl(), diag::objc_implementation_missing_impl,
-               getCategoryName(req->getDeclContext()), req);
+      // Append stub for this requirement into eventual fix-it.
+      swift::printRequirementStub(req, ext, ext->getSelfInterfaceType(),
+                                  ext->getStartLoc(), stubStream,
+                                  /*objCAttr=*/true);
+    }
 
-      // FIXME: Should give fix-it to add stub implementation
+    if (!stubs.empty()) {
+      diagnose(ext, diag::objc_implementation_missing_impls_fixit, numEmitted)
+        .fixItInsertAfter(ext->getBraces().Start, stubs);
     }
   }
 

lib/Sema/TypeCheckProtocol.cpp

@@ -3694,7 +3694,8 @@ static Type getTupleConformanceTypeWitness(DeclContext *dc,
 
 bool swift::
 printRequirementStub(ValueDecl *Requirement, DeclContext *Adopter,
-                     Type AdopterTy, SourceLoc TypeLoc, raw_ostream &OS) {
+                     Type AdopterTy, SourceLoc TypeLoc, raw_ostream &OS,
+                     bool withExplicitObjCAttr) {
   if (isa<ConstructorDecl>(Requirement)) {
     if (auto CD = Adopter->getSelfClassDecl()) {
       if (!CD->isSemanticallyFinal() && isa<ExtensionDecl>(Adopter)) {
@@ -3721,15 +3722,34 @@ printRequirementStub(ValueDecl *Requirement, DeclContext *Adopter,
   ExtraIndentStreamPrinter Printer(OS, StubIndent);
   Printer.printNewline();
 
+  PrintOptions Options = PrintOptions::printForDiagnostics(
+      AccessLevel::Private, Ctx.TypeCheckerOpts.PrintFullConvention);
+  Options.PrintDocumentationComments = false;
+  Options.PrintAccess = false;
+  Options.SkipAttributes = true;
+  Options.FunctionDefinitions = true;
+  Options.PrintAccessorBodiesInProtocols = true;
+  Options.FullyQualifiedTypesIfAmbiguous = true;
+
+  if (withExplicitObjCAttr) {
+    if (auto runtimeName = Requirement->getObjCRuntimeName()) {
+      llvm::SmallString<32> scratch;
+      Printer.printAttrName("@objc");
+      Printer << "(" << runtimeName->getString(scratch) << ")";
+      Printer.printNewline();
+      Options.ExcludeAttrList.push_back(DeclAttrKind::ObjC);
+    }
+  }
+
   AccessLevel Access =
     std::min(
       /* Access of the context */
       Adopter->getSelfNominalTypeDecl()->getFormalAccess(),
       /* Access of the protocol */
-      Requirement->getDeclContext()->getSelfProtocolDecl()->
-        getFormalAccess());
-  if (Access == AccessLevel::Public)
-    Printer << "public ";
+      Requirement->getDeclContext()->getSelfNominalTypeDecl()
+                      ->getFormalAccess());
+  if (Access > AccessLevel::Internal)
+    Printer.printKeyword(getAccessLevelSpelling(Access), Options, " ");
 
   if (auto MissingTypeWitness = dyn_cast<AssociatedTypeDecl>(Requirement)) {
     Printer << "typealias " << MissingTypeWitness->getName() << " = ";
@@ -3753,15 +3773,6 @@ printRequirementStub(ValueDecl *Requirement, DeclContext *Adopter,
       }
     }
 
-    PrintOptions Options = PrintOptions::printForDiagnostics(
-        AccessLevel::Private, Ctx.TypeCheckerOpts.PrintFullConvention);
-    Options.PrintDocumentationComments = false;
-    Options.PrintAccess = false;
-    Options.SkipAttributes = true;
-    Options.FunctionDefinitions = true;
-    Options.PrintAccessorBodiesInProtocols = true;
-    Options.FullyQualifiedTypesIfAmbiguous = true;
-
     bool AdopterIsClass = Adopter->getSelfClassDecl() != nullptr;
     // Skip 'mutating' only inside classes: mutating methods usually
     // don't have a sensible non-mutating implementation.

test/ClangImporter/rdar123543707.swift

@@ -7,8 +7,10 @@ import Module
 import Module_Private.Sub4
 
 @_objcImplementation extension Module {
-  // expected-warning@-1 {{extension for main class interface should provide implementation for class method 'version()'}}
-  // expected-warning@-2 {{extension for main class interface should provide implementation for class method 'alloc()'}}
+  // expected-warning@-1 {{extension for main class interface does not provide all required implementations}}
+  // expected-note@-2 {{missing class method 'version()'}}
+  // expected-note@-3 {{missing class method 'alloc()'}}
+  // expected-note@-4 {{add stubs for missing '@implementation' requirements}} {{40-40=\n    @objc(version)\n    open class func version() -> UnsafePointer<CChar>! {\n        <#code#>\n    \}\n\n    @objc(alloc)\n    open class func alloc() -> Self! {\n        <#code#>\n    \}\n}}
 }
 
 extension Module: @retroactive ModuleProto {} // no-error

test/decl/ext/objc_implementation.swift

@@ -5,16 +5,18 @@
 
 protocol EmptySwiftProto {}
 
+// expected-note@+1 {{previously implemented here}}
 @objc @implementation extension ObjCClass: EmptySwiftProto, EmptyObjCProto {
-  // expected-note@-1 {{previously implemented here}}
-  // expected-error@-2 {{extension for main class interface should provide implementation for instance method 'method(fromHeader4:)'}}
-  // expected-error@-3 {{extension for main class interface should provide implementation for property 'propertyFromHeader9'}}
-  // FIXME: give better diagnostic expected-error@-4 {{extension for main class interface should provide implementation for property 'propertyFromHeader8'}}
-  // FIXME: give better diagnostic expected-error@-5 {{extension for main class interface should provide implementation for property 'propertyFromHeader7'}}
-  // FIXME: give better diagnostic expected-error@-6 {{extension for main class interface should provide implementation for instance method 'method(fromHeader3:)'}}
-  // expected-error@-7 {{'@objc @implementation' extension cannot add conformance to 'EmptySwiftProto'; add this conformance with an ordinary extension}}
-  // expected-error@-8 {{'@objc @implementation' extension cannot add conformance to 'EmptyObjCProto'; add this conformance in the Objective-C header}}
-  // expected-error@-9 {{extension for main class interface should provide implementation for instance method 'extensionMethod(fromHeader2:)'}}
+  // expected-error@-1 {{extension for main class interface does not provide all required implementations}}
+  // expected-note@-2 {{missing instance method 'method(fromHeader4:)'}} {{none}}
+  // expected-note@-3 {{missing property 'propertyFromHeader9'}} {{none}}
+  // FIXME: give better diagnostic expected-note@-4 {{missing property 'propertyFromHeader8'}} {{none}}
+  // FIXME: give better diagnostic expected-note@-5 {{missing property 'propertyFromHeader7'}} {{none}}
+  // FIXME: give better diagnostic expected-note@-6 {{missing instance method 'method(fromHeader3:)'}} {{none}}
+  // expected-note@-7 {{missing instance method 'extensionMethod(fromHeader2:)'}} {{none}}
+  // expected-note@-8 {{add stubs for missing '@implementation' requirements}} {{77-77=\n    @objc(methodFromHeader3:)\n    open func method(fromHeader3 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(methodFromHeader4:)\n    open func method(fromHeader4 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(propertyFromHeader7)\n    open var propertyFromHeader7: Int32 {\n        get {\n            <#code#>\n        \}\n        set(propertyFromHeader7) {\n            <#code#>\n        \}\n    \}\n\n    @objc(propertyFromHeader8)\n    open var propertyFromHeader8: Int32 {\n        get {\n            <#code#>\n        \}\n        set(propertyFromHeader8) {\n            <#code#>\n        \}\n    \}\n\n    @objc(propertyFromHeader9)\n    open var propertyFromHeader9: Int32 {\n        get {\n            <#code#>\n        \}\n        set(propertyFromHeader9) {\n            <#code#>\n        \}\n    \}\n\n    @objc(extensionMethodFromHeader2:)\n    open func extensionMethod(fromHeader2 param: Int32) {\n        <#code#>\n    \}\n}}
+  // expected-error@-9 {{'@objc @implementation' extension cannot add conformance to 'EmptySwiftProto'; add this conformance with an ordinary extension}}
+  // expected-error@-10 {{'@objc @implementation' extension cannot add conformance to 'EmptyObjCProto'; add this conformance in the Objective-C header}}
 
   func method(fromHeader1: CInt) {
     // OK, provides an implementation for the header's method.
@@ -233,10 +235,12 @@ protocol EmptySwiftProto {}
   // expected-error@-1 {{property 'rdar122280735' of type '(() -> ()) -> Void' does not match type '(@escaping () -> Void) -> Void' declared by the header}}
 }
 
+// expected-note@+1 {{'PresentAdditions' previously declared here}}
 @objc(PresentAdditions) @implementation extension ObjCClass {
-  // expected-note@-1 {{'PresentAdditions' previously declared here}}
-  // expected-error@-2 {{extension for category 'PresentAdditions' should provide implementation for instance method 'categoryMethod(fromHeader4:)'}}
-  // FIXME: give better diagnostic expected-error@-3 {{extension for category 'PresentAdditions' should provide implementation for instance method 'categoryMethod(fromHeader3:)'}}
+  // expected-error@-1 {{extension for category 'PresentAdditions' does not provide all required implementations}}
+  // expected-note@-2 {{missing instance method 'categoryMethod(fromHeader4:)'}} {{none}}
+  // FIXME: give better diagnostic expected-note@-3 {{missing instance method 'categoryMethod(fromHeader3:)'}} {{none}}
+  // expected-note@-4 {{add stubs for missing '@implementation' requirements}} {{62-62=\n    @objc(categoryMethodFromHeader3:)\n    open func categoryMethod(fromHeader3 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(categoryMethodFromHeader4:)\n    open func categoryMethod(fromHeader4 param: Int32) {\n        <#code#>\n    \}\n}}
 
   func method(fromHeader3: CInt) {
     // FIXME: should emit expected-DISABLED-error@-1 {{instance method 'method(fromHeader3:)' should be implemented in extension for main class interface, not category 'PresentAdditions'}}
@@ -295,7 +299,9 @@ protocol EmptySwiftProto {}
 }
 
 @objc(SwiftNameTests) @implementation extension ObjCClass {
-  // expected-error@-1 {{extension for category 'SwiftNameTests' should provide implementation for instance method 'methodSwiftName6B()'}}
+  // expected-error@-1 {{extension for category 'SwiftNameTests' does not provide all required implementations}}
+  // expected-note@-2 {{missing instance method 'methodSwiftName6B()'}} {{none}}
+  // expected-note@-3 {{add stub for missing '@implementation' requirement}} {{60-60=\n    @objc(methodObjCName6B)\n    open func methodSwiftName6B() {\n        <#code#>\n    \}\n}}
 
   func methodSwiftName1() {
     // expected-error@-1 {{selector 'methodSwiftName1' for instance method 'methodSwiftName1()' not found in header; did you mean 'methodObjCName1'?}} {{3-3=@objc(methodObjCName1) }}
@@ -406,7 +412,9 @@ protocol EmptySwiftProto {}
 }
 
 @objc(Conformance) @implementation extension ObjCClass {
-  // expected-error@-1 {{extension for category 'Conformance' should provide implementation for instance method 'requiredMethod2()'}}
+  // expected-error@-1 {{extension for category 'Conformance' does not provide all required implementations}}
+  // expected-note@-2 {{missing instance method 'requiredMethod2()'}} {{none}}
+  // expected-note@-3 {{add stub for missing '@implementation' requirement}} {{57-57=\n    @objc(requiredMethod2)\n    open func requiredMethod2() {\n        <#code#>\n    \}\n}}
   // no-error concerning 'optionalMethod2()'
 
   func requiredMethod1() {}
@@ -437,7 +445,9 @@ protocol EmptySwiftProto {}
 }
 
 @objc(InvalidMembers) @implementation extension ObjCClass {
-  // expected-error@-1 {{extension for category 'InvalidMembers' should provide implementation for instance method 'unimplementedMember()'}}
+  // expected-error@-1 {{extension for category 'InvalidMembers' does not provide all required implementations}}
+  // expected-note@-2 {{missing instance method 'unimplementedMember()'}} {{none}}
+  // expected-note@-3 {{add stub for missing '@implementation' requirement}} {{60-60=\n    @objc(unimplementedMember)\n    open func unimplementedMember() {\n        <#code#>\n    \}\n}}
 
   func nonObjCMethod(_: EmptySwiftProto) {
     // expected-error@-1 {{method cannot be in an @objc @implementation extension of a class (without final or @nonobjc) because the type of the parameter cannot be represented in Objective-C}}

test/decl/ext/objc_implementation_class_extension.swift

@@ -4,12 +4,14 @@
 @_implementationOnly import objc_implementation_class_extension_internal
 
 @_objcImplementation extension ObjCClass {
-  // expected-warning@-1 {{extension for main class interface should provide implementation for instance method 'method(fromHeader2:)'}}
-  // expected-warning@-2 {{extension for main class interface should provide implementation for property 'propertyFromHeader2'}}
-  // expected-warning@-3 {{extension for main class interface should provide implementation for instance method 'otherModuleExtensionMethod(fromHeader2:)'}}
-  // expected-warning@-4 {{extension for main class interface should provide implementation for property 'otherModuleExtensionPropertyFromHeader2'}}
-  // expected-warning@-5 {{extension for main class interface should provide implementation for instance method 'extensionMethod(fromHeader2:)'}}
-  // expected-warning@-6 {{extension for main class interface should provide implementation for property 'extensionPropertyFromHeader2'}}
+  // expected-warning@-1 {{extension for main class interface does not provide all required implementations}}
+  // expected-note@-2 {{missing instance method 'method(fromHeader2:)'}} {{none}}
+  // expected-note@-3 {{missing property 'propertyFromHeader2'}} {{none}}
+  // expected-note@-4 {{missing instance method 'otherModuleExtensionMethod(fromHeader2:)'}} {{none}}
+  // expected-note@-5 {{missing property 'otherModuleExtensionPropertyFromHeader2'}} {{none}}
+  // expected-note@-6 {{missing instance method 'extensionMethod(fromHeader2:)'}} {{none}}
+  // expected-note@-7 {{missing property 'extensionPropertyFromHeader2'}} {{none}}
+  // expected-note@-8 {{add stubs for missing '@implementation' requirements}} {{43-43=\n    @objc(methodFromHeader2:)\n    open func method(fromHeader2 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(propertyFromHeader2)\n    open var propertyFromHeader2: Int32 {\n        get {\n            <#code#>\n        \}\n        set(propertyFromHeader2) {\n            <#code#>\n        \}\n    \}\n\n    @objc(otherModuleExtensionMethodFromHeader2:)\n    open func otherModuleExtensionMethod(fromHeader2 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(otherModuleExtensionPropertyFromHeader2)\n    open var otherModuleExtensionPropertyFromHeader2: Int32 {\n        get {\n            <#code#>\n        \}\n        set(otherModuleExtensionPropertyFromHeader2) {\n            <#code#>\n        \}\n    \}\n\n    @objc(extensionMethodFromHeader2:)\n    open func extensionMethod(fromHeader2 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(extensionPropertyFromHeader2)\n    open var extensionPropertyFromHeader2: Int32 {\n        get {\n            <#code#>\n        \}\n        set(extensionPropertyFromHeader2) {\n            <#code#>\n        \}\n    \}\n}}
 
   @objc func method(fromHeader1: CInt) {}
   @objc private func method(fromHeader2: CInt) {}