Revert "[GSB] SE-0157: Reprocess delayed requirements when we need a complete PA."

This reverts commit ded45a6.

This seems to slow down type checking of Swift.o by more than 3x.

Author: rudkx

lib/AST/GenericSignatureBuilder.cpp

@@ -90,13 +90,6 @@ struct GenericSignatureBuilder::Implementation {
   /// The set of requirements that have been delayed for some reason.
   SmallVector<DelayedRequirement, 4> DelayedRequirements;
 
-  /// The generation number, which is incremented whenever we successfully
-  /// introduce a new constraint.
-  unsigned Generation = 0;
-
-  /// The generation at which we last processed all of the delayed requirements.
-  unsigned LastProcessedGeneration = 0;
-
 #ifndef NDEBUG
   /// Whether we've already finalized the builder.
   bool finalized = false;
@@ -1406,9 +1399,6 @@ bool PotentialArchetype::addConformance(ProtocolDecl *proto,
     return false;
   }
 
-  // Bump the generation.
-  ++builder.Impl->Generation;
-
   // Add the conformance along with this constraint.
   equivClass->conformsTo[proto].push_back({this, proto, source});
   ++NumConformanceConstraints;
@@ -1876,12 +1866,6 @@ PotentialArchetype *PotentialArchetype::updateNestedTypeForConformance(
   if (!assocType && !concreteDecl)
     return nullptr;
 
-  // If we were asked for a complete, well-formed archetype, make sure we
-  // process delayed requirements if anything changed.
-  SWIFT_DEFER {
-    getBuilder()->processDelayedRequirements();
-  };
-
   Identifier name = assocType ? assocType->getName() : concreteDecl->getName();
   ProtocolDecl *proto =
     assocType ? assocType->getProtocol()
@@ -1916,9 +1900,6 @@ PotentialArchetype *PotentialArchetype::updateNestedTypeForConformance(
     switch (kind) {
     case ArchetypeResolutionKind::CompleteWellFormed:
     case ArchetypeResolutionKind::WellFormed: {
-      // Bump the generation count, because we created a new archetype.
-      ++getBuilder()->Impl->Generation;
-
       if (assocType)
         resultPA = new PotentialArchetype(this, assocType);
       else
@@ -2837,9 +2818,6 @@ ConstraintResult GenericSignatureBuilder::addLayoutRequirement(
     return ConstraintResult::Resolved;
   }
 
-  // Bump the generation.
-  ++Impl->Generation;
-
   auto pa = resolvedSubject->getPotentialArchetype();
   return addLayoutRequirementDirect(pa, layout, source.getSource(pa));
 }
@@ -2924,9 +2902,6 @@ ConstraintResult GenericSignatureBuilder::addSuperclassRequirementDirect(
     .push_back(ConcreteConstraint{T, superclass, source});
   ++NumSuperclassConstraints;
 
-  // Bump the generation.
-  ++Impl->Generation;
-
   // Update the equivalence class with the constraint.
   updateSuperclass(T, superclass, source);
   return ConstraintResult::Resolved;
@@ -3086,9 +3061,6 @@ GenericSignatureBuilder::addSameTypeRequirementBetweenArchetypes(
   if (T1 == T2)
     return ConstraintResult::Resolved;
 
-  // Bump the generation.
-  ++Impl->Generation;
-
   unsigned nestingDepth1 = T1->getNestingDepth();
   unsigned nestingDepth2 = T2->getNestingDepth();
 
@@ -3224,9 +3196,6 @@ ConstraintResult GenericSignatureBuilder::addSameTypeRequirementToConcrete(
                                       ConcreteConstraint{T, Concrete, Source});
   ++NumConcreteTypeConstraints;
 
-  // Bump the generation.
-  ++Impl->Generation;
-
   // If we've already been bound to a type, match that type.
   if (equivClass->concreteType) {
     return addSameTypeRequirement(equivClass->concreteType, Concrete, Source,
@@ -4009,13 +3978,6 @@ static GenericSignatureBuilder::UnresolvedType asUnresolvedType(
 }
 
 void GenericSignatureBuilder::processDelayedRequirements() {
-  // If we're already up-to-date, do nothing.
-  if (Impl->Generation == Impl->LastProcessedGeneration) return;
-
-  SWIFT_DEFER {
-    Impl->LastProcessedGeneration = Impl->Generation;
-  };
-
   bool anySolved = !Impl->DelayedRequirements.empty();
   while (anySolved) {
     // Steal the delayed requirements so we can reprocess them.

test/decl/protocol/recursive_requirement_ok.swift

@@ -9,6 +9,5 @@ protocol P {
 func testP<T: P>(_ t: T) {
   testP(t.assoc)
   testP(t.assoc.assoc)
-  testP(t.assoc.assoc.assoc)
-  testP(t.assoc.assoc.assoc.assoc.assoc.assoc.assoc)
+  testP(t.assoc.assoc.assoc) // FIXME: expected-error{{argument type 'T.Assoc.Assoc.Assoc' does not conform to expected type 'P'}}
 }