Allow package(set) at the top level decl site

Treat `package` as a non-contextual keyword when applicable
Add tests
Resolves rdar://105978922, rdar://104931420

Author: elsh

lib/Parse/ParseDecl.cpp

@@ -4886,6 +4886,50 @@ bool Parser::isStartOfSwiftDecl(bool allowPoundIfAttributes) {
   if (Tok.isContextualKeyword("macro") && Tok2.is(tok::identifier))
     return true;
 
+  if (Tok.isContextualKeyword("package")) {
+    // If `case` is the next token after `return package` statement,
+    // E.g.
+    // switch package {
+    //   case .x: return package
+    //   case .y: return nil
+    // }
+    // currently it errors (this is also true for `open`).
+    //
+    // If a non-contextual keyword was used in the above example, this
+    // function hits the line from above:
+    // ```
+    // if (!Tok.isContextualDeclKeyword())
+    //   return false;
+    // ```
+    // thus we return false here as well, i.e. treat it as a non-contextual
+    // keyword.
+    if (Tok2.getKind() == tok::kw_case)
+      return false;
+    
+    // Handle 'package(set)' access modifier
+    auto DAK = DeclAttribute::getAttrKindFromString(Tok.getText());
+    if (DAK != DAK_Count && DeclAttribute::isDeclModifier(DAK)) {
+      BacktrackingScope backtrack(*this);
+      // First consume `package`
+      consumeToken();
+      // Eat paren after modifier name; e.g. `package(set)`, similar to
+      // `private(set)` described above in the `if (Tok.isKeyword())` block
+      if (consumeIf(tok::l_paren)) {
+        while (Tok.isNot(tok::r_brace, tok::eof, tok::pound_endif)) {
+          if (consumeIf(tok::r_paren))
+            break;
+          // If we found the start of a decl while trying to skip over the
+          // paren, then we have something incomplete like 'package('. Return
+          // true for better recovery.
+          if (isStartOfSwiftDecl(/*allowPoundIfAttributes=*/false))
+            return true;
+          skipSingle();
+        }
+      }
+      return isStartOfSwiftDecl(/*allowPoundIfAttributes=*/false);
+    }
+  }
+
   // If the next token is obviously not the start of a decl, bail early.
   if (!isKeywordPossibleDeclStart(Context.LangOpts, Tok2))
     return false;

test/Sema/accessibility_package_contextual_keyword.swift

@@ -0,0 +1,64 @@
+// RUN: %empty-directory(%t)
+// RUN: %{python} %utils/split_file.py -o %t %s
+
+// RUN: %target-swift-frontend-typecheck -verify -disable-availability-checking %t/main.swift -package-name myPkg
+// RUN: %target-swift-frontend-typecheck -verify -disable-availability-checking %t/A.swift -package-name myPkg
+// RUN: %target-swift-frontend-typecheck -verify -disable-availability-checking %t/B.swift -package-name myPkg
+// RUN: %target-swift-frontend-typecheck -verify -disable-availability-checking %t/D.swift -package-name myPkg
+// RUN: not %target-swift-frontend-typecheck -verify -disable-availability-checking %t/C.swift -package-name myPkg 2>&1 | %FileCheck %s
+
+// BEGIN main.swift
+package(set) public var a: String // should pass when `package` modifier is used at top level decls
+public package(set) var b: String
+package let c: Int
+package var d: Int
+package func f() {}
+
+// BEGIN A.swift
+package class package { // package can be a type name
+  package init() {}
+  package var package: String?  // package can be a var name
+}
+
+package class pkg {
+  package init() {}
+  package func package() {} // package can be a func name
+  package func package(arg: Int) {}
+  package func package(_ arg: Double) {}
+}
+
+public class MyClass {
+  var myVar1: package = package()
+  var myVar2: pkg = pkg()
+  func myFunc() {
+    _ = myVar1.package
+    myVar2.package()
+    myVar2.package(arg: 1)
+    myVar2.package(2.0)
+  }
+}
+
+// BEGIN B.swift
+public class Foo {
+  package(set) public var x: String?
+  public package(set) var y: Int?
+}
+
+// BEGIN C.swift
+public class Bar {
+  package package(set) package: String? // CHECK: warning: 'package(set)' modifier is redundant for a package var
+  package(set) package package: String? // CHECK: warning: 'package(set)' modifier is redundant for a package var
+}
+
+// BEGIN D.swift
+enum MyColor {
+  case red, green, blue
+}
+let packages: [MyColor] = [MyColor.red, MyColor.blue].compactMap { package in
+  switch package {
+    case .blue: return package // Should not error when `case` follows the `package` contextual keyword
+    case .red: return package
+    default: return nil
+  }
+}
+

test/attr/accessibility.swift

@@ -35,15 +35,10 @@ fileprivate(set)
 public
 var customSetter2 = 0
 
-// FIXME: rdar://104931420 folowing should not error
-// expected-error @+2{{cannot find 'package' in scope}}{{none}}
-// expected-error @+1{{cannot find 'set' in scope; did you mean 'Set'?}}{{9-12=Set}}
 package(set)
 public
 var customSetter3 = 0
 
-// FIXME: rdar://104931420 folowing should not error
-// expected-error @+1{{expected expression}}
 public
 package(set)
 var customSetter4 = 0
@@ -66,6 +61,14 @@ public(set) // expected-error {{duplicate modifier}}
 private // expected-error {{duplicate modifier}}
 var customSetterDuplicateAttrsAllAround = 0
 
+private(set) // expected-note {{modifier already specified here}}
+package(set) // expected-error {{duplicate modifier}}
+var customSetterDuplicateAttr2 = 0
+
+package(set) // expected-note {{modifier already specified here}}
+public(set) // expected-error {{duplicate modifier}}
+public var customSetterDuplicateAttr3 = 0
+
 private(get) // expected-error{{expected 'set' as subject of 'private' modifier}}
 var invalidSubject = 0
 
@@ -75,6 +78,13 @@ var invalidSubject2 = 0
 private(a bunch of random tokens) // expected-error{{expected 'set' as subject of 'private' modifier}} expected-error{{expected declaration}}
 var invalidSubject3 = 0
 
+
+package(get) // expected-error{{expected 'set' as subject of 'package' modifier}}
+var invalidSubject4 = 0
+
+package(42) // expected-error{{expected 'set' as subject of 'package' modifier}}
+var invalidSubject5 = 0
+
 private(set // expected-error{{expected ')' in 'private' modifier}}
 var unterminatedSubject = 0
 
@@ -132,7 +142,9 @@ private protocol TestProtocol {
 public(set) func publicSetFunc() {} // expected-error {{'public' modifier cannot be applied to this declaration}} {{1-13=}}
 
 public(set) var defaultVis = 0 // expected-error {{internal variable cannot have a public setter}}
-
+package(set) var defaultVisPkg = 0 // expected-error {{internal variable cannot have a package setter}}
+package(set) package var defaultVisPkgPkg = 0 // expected-warning {{'package(set)' modifier is redundant for a package var}}
+package(set) public var defaultVisPkgOK = 0 // OK
 internal(set) private var privateVis = 0 // expected-error {{private variable cannot have an internal setter}}
 private(set) var defaultVisOK = 0
 private(set) public var publicVis = 0
@@ -144,8 +156,15 @@ private(set) var computedRW: Int {
   get { return 42 }
   set { }
 }
+
+package(set) public var computedPkg: Int { // expected-error {{'package(set)' modifier cannot be applied to read-only variables}} {{1-14=}}
+  return 42
+}
+
 private(set) let constant = 42 // expected-error {{'private(set)' modifier cannot be applied to constants}} {{1-14=}}
 
+package(set) public let constantPkg = 42 // expected-error {{'package(set)' modifier cannot be applied to constants}} {{1-14=}}
+
 public struct Properties {
   private(set) var stored = 42
   private(set) var computed: Int { // expected-error {{'private(set)' modifier cannot be applied to read-only properties}} {{3-16=}}
@@ -155,14 +174,30 @@ public struct Properties {
     get { return 42 }
     set { }
   }
+
+  package(set) public var computedRWPkg: Int {
+    get { return 42 }
+    set { }
+  }
+
+  public package(set) var computedR: Int { // expected-error {{'package(set)' modifier cannot be applied to read-only properties}} {{10-23=}}
+    return 42
+  }
+
   private(set) let constant = 42 // expected-error {{'private(set)' modifier cannot be applied to read-only properties}} {{3-16=}}
+  package(set) public let constantPkg = 42 // expected-error {{'package(set)' modifier cannot be applied to read-only properties}} {{3-16=}}
+  package(set) var defaultVisPkg = 42 // expected-error {{internal property cannot have a package setter}}
   public(set) var defaultVis = 0 // expected-error {{internal property cannot have a public setter}}
   open(set) var defaultVis2 = 0 // expected-error {{internal property cannot have an open setter}}
 
   public(set) subscript(a a: Int) -> Int { // expected-error {{internal subscript cannot have a public setter}}
     get { return 0 }
     set {}
   }
+  package(set) subscript(p p: Int) -> Int { // expected-error {{internal subscript cannot have a package setter}}
+    get { return 0 }
+    set {}
+  }
   internal(set) private subscript(b b: Int) -> Int { // expected-error {{private subscript cannot have an internal setter}}
     get { return 0 }
     set {}
@@ -180,6 +215,10 @@ public struct Properties {
 }
 
 private extension Properties {
+  package(set) var extPropPkg: Int { // expected-error {{private property cannot have a package setter}}
+    get { return 42 }
+    set { }
+  }
   public(set) var extProp: Int { // expected-error {{private property cannot have a public setter}}
     get { return 42 }
     set { }
@@ -198,11 +237,13 @@ private(set) extension Properties : EmptyProto2 {} // expected-error {{'private'
 package protocol EmptyProto3 {}
 package protocol EmptyProto4 {}
 public protocol EmptyProto5 {}
+public protocol EmptyProto6 {}
 
 private extension Properties : EmptyProto3 {} // expected-error {{'private' modifier cannot be used with extensions that declare protocol conformances}} {{1-9=}}
 private(set) extension Properties : EmptyProto4 {} // expected-error {{'private' modifier cannot be applied to this declaration}} {{1-14=}}
 
 package extension Properties : EmptyProto5 {} // expected-error {{'package' modifier cannot be used with extensions that declare protocol conformances}} {{1-9=}}
+package(set) extension Properties : EmptyProto6 {} // expected-error {{'package' modifier cannot be applied to this declaration}} {{1-14=}}
 
 public struct PublicStruct {}
 package struct PackageStruct {} // expected-note * {{declared here}}