AST: Remove ProtocolConformanceState::CheckingTypeWitnesses

Author: slavapestov

include/swift/AST/ProtocolConformance.h

@@ -86,8 +86,6 @@ enum class ProtocolConformanceState {
   Complete = 0,
   /// The conformance is known but is not yet complete.
   Incomplete,
-  /// The conformance's type witnesses are currently being resolved.
-  CheckingTypeWitnesses,
   /// The conformance is being checked.
   Checking,
 
@@ -225,7 +223,6 @@ class alignas(1 << DeclAlignInBits) ProtocolConformance
   /// Determine whether this conformance is incomplete.
   bool isIncomplete() const {
     return getState() == ProtocolConformanceState::Incomplete ||
-           getState() == ProtocolConformanceState::CheckingTypeWitnesses ||
            getState() == ProtocolConformanceState::Checking;
   }
 

lib/AST/ASTVerifier.cpp

@@ -2803,7 +2803,6 @@ class Verifier : public ASTWalker {
         // Ignore incomplete conformances; we didn't need them.
         return;
 
-      case ProtocolConformanceState::CheckingTypeWitnesses:
       case ProtocolConformanceState::Checking:
         dumpRef(decl);
         Out << " has a protocol conformance that is still being checked "

lib/AST/ProtocolConformance.cpp

@@ -479,7 +479,12 @@ NormalProtocolConformance::getTypeWitnessAndDecl(AssociatedTypeDecl *assocType,
 
   // If this conformance is in a state where it is inferring type witnesses but
   // we didn't find anything, fail.
-  if (getState() == ProtocolConformanceState::CheckingTypeWitnesses) {
+  //
+  // FIXME: This is unsound, because we may not have diagnosed anything but
+  // still end up with an ErrorType in the AST.
+  if (getDeclContext()->getASTContext().evaluator.hasActiveRequest(
+         ResolveTypeWitnessesRequest{
+             const_cast<NormalProtocolConformance *>(this)})) {
     return { Type(), nullptr };
   }
 

lib/AST/SubstitutionMap.cpp

@@ -436,10 +436,13 @@ SubstitutionMap::lookupConformance(CanType type, ProtocolDecl *proto) const {
     if (!normal->hasComputedAssociatedConformances()) {
       // If we're in the process of checking the type witnesses, fail
       // gracefully.
-      // FIXME: Seems like we should be able to get at the intermediate state
-      // to use that.
-      if (normal->getState() == ProtocolConformanceState::CheckingTypeWitnesses)
+      //
+      // FIXME: This is unsound, because we may not have diagnosed anything but
+      // still end up with an ErrorType in the AST.
+      if (proto->getASTContext().evaluator.hasActiveRequest(
+            ResolveTypeWitnessesRequest{normal})) {
         return ProtocolConformanceRef::forInvalid();
+      }
     }
 
     // Get the associated conformance.

lib/Sema/AssociatedTypeInference.cpp

@@ -3515,12 +3515,7 @@ auto AssociatedTypeInference::solve()
                           << ": " << conformance->getProtocol()->getName()
                           << " ============\n";);
 
-  // Track when we are checking type witnesses.
-  ProtocolConformanceState initialState = conformance->getState();
-  conformance->setState(ProtocolConformanceState::CheckingTypeWitnesses);
   SWIFT_DEFER {
-    conformance->setState(initialState);
-
     LLVM_DEBUG(llvm::dbgs() << "============ Finish " << conformance->getType()
                             << ": " << conformance->getProtocol()->getName()
                             << " ============\n";);

lib/Sema/TypeCheckNameLookup.cpp

@@ -22,6 +22,7 @@
 #include "swift/AST/NameLookup.h"
 #include "swift/AST/NameLookupRequests.h"
 #include "swift/AST/ProtocolConformance.h"
+#include "swift/AST/TypeCheckRequests.h"
 #include "swift/Basic/TopCollection.h"
 #include <algorithm>
 
@@ -496,13 +497,15 @@ LookupTypeResult TypeChecker::lookupMemberType(DeclContext *dc,
       }
 
       // Use the type witness.
-      auto concrete = conformance.getConcrete();
+      auto *concrete = conformance.getConcrete();
+      auto *normal = concrete->getRootNormalConformance();
 
       // This is the only case where NormalProtocolConformance::
       // getTypeWitnessAndDecl() returns a null type.
-      if (concrete->getState() ==
-          ProtocolConformanceState::CheckingTypeWitnesses)
+      if (dc->getASTContext().evaluator.hasActiveRequest(
+            ResolveTypeWitnessesRequest{normal})) {
         continue;
+      }
 
       auto *typeDecl =
         concrete->getTypeWitnessAndDecl(assocType).getWitnessDecl();

lib/Sema/TypeCheckProtocol.cpp

@@ -2178,7 +2178,6 @@ checkIndividualConformance(NormalProtocolConformance *conformance) {
       // Check the rest of the conformance below.
       break;
 
-    case ProtocolConformanceState::CheckingTypeWitnesses:
     case ProtocolConformanceState::Checking:
     case ProtocolConformanceState::Complete:
       // Nothing to do.