Remove -enable-protocol-typealiases staging flag

It looks like migration fixits are done, and this doesn't
expose any new bugs that were not possible before, because
you could already define typealiases inside protocol
extensions.

To prevent some compiler_crasher regressions, add a simple
circularity-breaking hack. I'll need to do a sweep to clean
these up some day soon.

Author: slavapestov

include/swift/AST/DiagnosticsParse.def

@@ -778,8 +778,6 @@ ERROR(expected_close_after_else_directive,none,
       "further conditions after #else are unreachable", ())
 
 /// Associatedtype Statement
-WARNING(typealias_in_protocol_deprecated,none,
-      "use of 'typealias' to declare associated types is deprecated; use 'associatedtype' instead", ())
 ERROR(typealias_inside_protocol_without_type,none,
       "typealias is missing an assigned type; use 'associatedtype' to define an associated type requirement", ())
 ERROR(associatedtype_outside_protocol,none,

include/swift/Basic/LangOptions.h

@@ -170,9 +170,6 @@ namespace swift {
     /// Enable the Swift 3 migration via Fix-Its.
     bool Swift3Migration = false;
 
-    /// Enable typealiases in protocols.
-    bool EnableProtocolTypealiases = false;
-
     /// Sets the target we are building for and updates platform conditions
     /// to match.
     ///

include/swift/Option/FrontendOptions.td

@@ -352,9 +352,6 @@ def enable_resilience : Flag<["-"], "enable-resilience">,
 def group_info_path : Separate<["-"], "group-info-path">,
   HelpText<"The path to collect the group information of the compiled module">;
 
-def enable_protocol_typealiases: Flag<["-"], "enable-protocol-typealiases">,
-  HelpText<"Enable typealiases inside protocol declarations">;
-  
 def enable_id_as_any: Flag<["-"], "enable-id-as-any">,
   HelpText<"Enable importing ObjC 'id' as Swift 'Any' type">;
 

lib/Frontend/CompilerInvocation.cpp

@@ -778,7 +778,6 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
   Opts.InferImportAsMember |= Args.hasArg(OPT_enable_infer_import_as_member);
 
   Opts.EnableThrowWithoutTry |= Args.hasArg(OPT_enable_throw_without_try);
-  Opts.EnableProtocolTypealiases |= Args.hasArg(OPT_enable_protocol_typealiases);
   Opts.EnableIdAsAny |= Args.hasArg(OPT_enable_id_as_any);
 
   if (auto A = Args.getLastArg(OPT_enable_objc_attr_requires_foundation_module,

lib/Parse/ParseDecl.cpp

@@ -2083,12 +2083,7 @@ ParserStatus Parser::parseDecl(ParseDeclOptions Flags,
       break;
     }
     case tok::kw_typealias:
-      if (Flags.contains(PD_InProtocol) &&
-          !Context.LangOpts.EnableProtocolTypealiases) {
-        DeclResult = parseDeclAssociatedType(Flags, Attributes);
-      } else {
-        DeclResult = parseDeclTypeAlias(Flags, Attributes);
-      }
+      DeclResult = parseDeclTypeAlias(Flags, Attributes);
       Status = DeclResult;
       break;
     case tok::kw_associatedtype:
@@ -2979,10 +2974,7 @@ ParserResult<TypeDecl> Parser::parseDeclAssociatedType(Parser::ParseDeclOptions
   // ask us to fix up leftover Swift 2 code intending to be an associatedtype.
   if (Tok.is(tok::kw_typealias)) {
     AssociatedTypeLoc = consumeToken(tok::kw_typealias);
-    auto diagnosis = Context.LangOpts.EnableProtocolTypealiases ?
-      diag::typealias_inside_protocol_without_type :
-      diag::typealias_in_protocol_deprecated;
-    diagnose(AssociatedTypeLoc, diagnosis)
+    diagnose(AssociatedTypeLoc, diag::typealias_inside_protocol_without_type)
         .fixItReplace(AssociatedTypeLoc, "associatedtype");
   } else {
     AssociatedTypeLoc = consumeToken(tok::kw_associatedtype);

lib/Sema/TypeCheckType.cpp

@@ -651,6 +651,10 @@ static Type resolveTypeDecl(TypeChecker &TC, TypeDecl *typeDecl, SourceLoc loc,
   } else {
     // Validate the declaration.
     TC.validateDecl(typeDecl);
+
+    // FIXME: More principled handling of circularity.
+    if (!isa<AssociatedTypeDecl>(typeDecl) && !typeDecl->hasType())
+      return ErrorType::get(TC.Context);
   }
 
   // Resolve the type declaration to a specific type. How this occurs

test/Generics/associated_types.swift

@@ -173,7 +173,7 @@ struct C<a : B> : B { // expected-error {{type 'C<a>' does not conform to protoc
 
 // SR-511
 protocol sr511 {
-  typealias Foo // expected-warning {{use of 'typealias' to declare associated types is deprecated; use 'associatedtype' instead}} 
+  typealias Foo // expected-error {{typealias is missing an assigned type; use 'associatedtype' to define an associated type requirement}}
 }
 
 associatedtype Foo = Int // expected-error {{associated types can only be defined in a protocol; define a type or introduce a 'typealias' to satisfy an associated type requirement}}

test/decl/typealias/protocol.swift

@@ -1,4 +1,4 @@
-// RUN: %target-parse-verify-swift -enable-protocol-typealiases
+// RUN: %target-parse-verify-swift
 
 // Tests for typealias inside protocols
 

validation-test/compiler_crashers/28268-swift-type-transform.swift renamed to validation-test/compiler_crashers_fixed/28268-swift-type-transform.swift

@@ -5,6 +5,6 @@
 // See http://swift.org/LICENSE.txt for license information
 // See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 
-// RUN: not --crash %target-swift-frontend %s -parse
+// RUN: not %target-swift-frontend %s -parse
 var:{protocol a{struct A:a
 typealias e=A.e

validation-test/compiler_crashers/28333-swift-typedecl-getdeclaredtype.swift renamed to validation-test/compiler_crashers_fixed/28333-swift-typedecl-getdeclaredtype.swift

@@ -5,7 +5,7 @@
 // See http://swift.org/LICENSE.txt for license information
 // See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 
-// RUN: not --crash %target-swift-frontend %s -parse
+// RUN: not %target-swift-frontend %s -parse
 // REQUIRES: asserts
 protocol c{{}
 func c:f.a

validation-test/compiler_crashers/28360-swift-archetypebuilder-maptypeoutofcontext.swift renamed to validation-test/compiler_crashers_fixed/28360-swift-archetypebuilder-maptypeoutofcontext.swift

@@ -5,6 +5,6 @@
 // See http://swift.org/LICENSE.txt for license information
 // See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 
-// RUN: not --crash %target-swift-frontend %s -parse
+// RUN: not %target-swift-frontend %s -parse
 // REQUIRES: asserts
 struct A<f{protocol a{typealias f=B}struct B{let c=A.a as a

validation-test/compiler_crashers/28364-swift-typechecker-addimplicitconstructors.swift renamed to validation-test/compiler_crashers_fixed/28364-swift-typechecker-addimplicitconstructors.swift

@@ -5,7 +5,7 @@
 // See http://swift.org/LICENSE.txt for license information
 // See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 
-// RUN: not --crash %target-swift-frontend %s -parse
+// RUN: not %target-swift-frontend %s -parse
 // REQUIRES: asserts
 {
 protocol d{