[Parse] Disallow use of actor as a declaration modifier

`actor` is a standalone contextual keyword now and should
be treated as such, `actor class` is no longer allowed
and results in a parse error.

Resolves: rdar://75753598

Author: xedin

lib/Parse/ParseDecl.cpp

@@ -3612,41 +3612,25 @@ bool Parser::parseDeclModifierList(DeclAttributes &Attributes,
         // that scope, so we have to store enough state to emit the diagnostics
         // outside of the scope.
         bool isActorModifier = false;
-        bool isClassNext = false;
         SourceLoc actorLoc = Tok.getLoc();
-        SourceLoc classLoc;
+
         {
           BacktrackingScope Scope(*this);
 
-          // Is this the class token before the identifier?
-          auto atClassDecl = [this]() -> bool {
-            return peekToken().is(tok::identifier) ||
-              Tok.is(tok::kw_class) ||
-              Tok.is(tok::kw_enum) ||
-              Tok.is(tok::kw_struct);
-          };
           consumeToken(); // consume actor
           isActorModifier = isStartOfSwiftDecl();
-          if (isActorModifier) {
-            isClassNext = atClassDecl();
-            while (!atClassDecl())
-              consumeToken();
-            classLoc = Tok.getLoc();
-          }
         }
 
         if (!isActorModifier)
           break;
 
-        auto diag = diagnose(actorLoc,
-            diag::renamed_platform_condition_argument, "actor class", "actor");
-        if (isClassNext)
-          diag.fixItRemove(classLoc);
-        else
-          diag.fixItReplace(classLoc, "actor")
-              .fixItRemove(actorLoc);
-        Attributes.add(new (Context) ActorAttr({}, Tok.getLoc()));
-        consumeToken();
+        // Actor is a standalone keyword now, so it can't be used
+        // as a modifier. Let's diagnose and recover.
+        isError = true;
+
+        consumeToken(); // consume 'actor'
+
+        diagnose(actorLoc, diag::keyword_cant_be_identifier, Tok.getText());
         continue;
       }
 

lib/Sema/TypeCheckConcurrency.cpp

@@ -107,8 +107,7 @@ bool IsActorRequest::evaluate(
   if (!classDecl)
     return false;
 
-  return classDecl->isExplicitActor() ||
-      classDecl->getAttrs().getAttribute<ActorAttr>();
+  return classDecl->isExplicitActor();
 }
 
 bool IsDefaultActorRequest::evaluate(

test/SourceKit/CursorInfo/cursor_info_concurrency.swift

@@ -7,14 +7,6 @@ func test(act: MyActor) async throws {
     try await act.asyncFunc {}
 }
 
-public actor class MyActorClass {
-  public func asyncFunc(fn: () async -> Void) async throws {}
-}
-
-func test(act: MyActorClass) async throws {
-    try await act.asyncFunc {}
-}
-
 // BEGIN App.swift
 import MyModule
 
@@ -35,15 +27,9 @@ func test(act: MyActor) async throws {
 // RUN: %sourcekitd-test -req=cursor -pos=5:16 %t/MyModule.swift -- %t/MyModule.swift -target %target-triple -Xfrontend -enable-experimental-concurrency | %FileCheck -check-prefix=ACTOR %s
 // RUN: %sourcekitd-test -req=cursor -pos=6:19  %t/MyModule.swift -- %t/MyModule.swift -target %target-triple -Xfrontend -enable-experimental-concurrency | %FileCheck -check-prefix=FUNC %s
 
-// RUN: %sourcekitd-test -req=cursor -pos=9:20  %t/MyModule.swift -- %t/MyModule.swift -target %target-triple -Xfrontend -enable-experimental-concurrency | %FileCheck -check-prefix=CLASSACTOR %s
-// RUN: %sourcekitd-test -req=cursor -pos=13:16  %t/MyModule.swift -- %t/MyModule.swift -target %target-triple -Xfrontend -enable-experimental-concurrency | %FileCheck -check-prefix=CLASSACTOR %s
-
 // ACTOR: <Declaration>public actor MyActor</Declaration>
 // ACTOR: <decl.class><syntaxtype.keyword>public</syntaxtype.keyword> <syntaxtype.keyword>actor</syntaxtype.keyword> <decl.name>MyActor</decl.name></decl.class>
 
-// CLASSACTOR: <Declaration>public actor class MyActorClass</Declaration>
-// CLASSACTOR: <decl.class><syntaxtype.keyword>public</syntaxtype.keyword> <syntaxtype.keyword>actor</syntaxtype.keyword> <syntaxtype.keyword>class</syntaxtype.keyword> <decl.name>MyActorClass</decl.name></decl.class>
-
 // FUNC: <Declaration>public func asyncFunc(fn: () async -&gt; <Type usr="s:s4Voida">Void</Type>) async throws</Declaration>
 // FUNC: <decl.function.method.instance><syntaxtype.keyword>public</syntaxtype.keyword> <syntaxtype.keyword>func</syntaxtype.keyword> <decl.name>asyncFunc</decl.name>(<decl.var.parameter><decl.var.parameter.argument_label>fn</decl.var.parameter.argument_label>: <decl.var.parameter.type>() <syntaxtype.keyword>async</syntaxtype.keyword> -&gt; <decl.function.returntype><ref.typealias usr="s:s4Voida">Void</ref.typealias></decl.function.returntype></decl.var.parameter.type></decl.var.parameter>) <syntaxtype.keyword>async</syntaxtype.keyword> <syntaxtype.keyword>throws</syntaxtype.keyword></decl.function.method.instance>
 

test/attr/attr_objc_async.swift

@@ -47,13 +47,11 @@ actor MyActor {
   @objc nonisolated func synchronousGood() { }
 }
 
-// CHECK: actor class MyActor2
 actor class MyActor2 { }
-// expected-warning@-1{{'actor class' has been renamed to 'actor'}}{{7-13=}}
+// expected-error@-1 {{keyword 'class' cannot be used as an identifier here}}
 
 // CHECK: @objc actor MyObjCActor
 @objc actor MyObjCActor: NSObject { }
 
-// CHECK: @objc actor class MyObjCActor2
 @objc actor class MyObjCActor2: NSObject {}
-// expected-warning@-1{{'actor class' has been renamed to 'actor'}}{{13-19=}}
+// expected-error@-1 {{keyword 'class' cannot be used as an identifier here}}

test/decl/class/actor/basic.swift

@@ -9,20 +9,18 @@ class MyActorSubclass1: MyActor { } // expected-error{{actor types do not suppor
 
 actor MyActorSubclass2: MyActor { } // expected-error{{actor types do not support inheritance}}
 
-// expected-warning@+1{{'actor class' has been renamed to 'actor'}}{{7-13=}}
+// expected-error@+1{{keyword 'class' cannot be used as an identifier here}}
 actor class MyActorClass { }
 
 class NonActor { }
 
 actor NonActorSubclass : NonActor { } // expected-error{{actor types do not support inheritance}}
 
-// expected-warning@+1{{'actor class' has been renamed to 'actor'}}{{14-20=}}
+// expected-error@+1{{keyword 'class' cannot be used as an identifier here}}
 public actor class BobHope {}
-// expected-warning@+1{{'actor class' has been renamed to 'actor'}}{{14-19=actor}}{{1-7=}}
+// expected-error@+1{{keyword 'public' cannot be used as an identifier here}}
 actor public class BarbraStreisand {}
-// expected-warning@+2{{'actor class' has been renamed to 'actor'}}{{14-21=}}
-// expected-error@+1{{'actor' may only be used on 'class' declarations}}
+// expected-error@+1{{keyword 'struct' cannot be used as an identifier here}}
 public actor struct JulieAndrews {}
-// expected-warning@+2{{'actor class' has been renamed to 'actor'}}{{14-18=actor}}{{1-7=}}
-// expected-error@+1{{'actor' may only be used on 'class' declarations}}
+// expected-error@+1{{keyword 'public' cannot be used as an identifier here}}
 actor public enum TomHanks {}