[AST] Eliminate the HasValidatedLayout bit.

We handle layout through finalization of the declaration,
which already has its own approach to eliminating redundant work.
We don’t need an extra bit getting in the way.

Author: DougGregor

include/swift/AST/Decl.h

@@ -480,17 +480,13 @@ class alignas(1 << DeclAlignInBits) Decl {
     IsDebuggerAlias : 1
   );
 
-  SWIFT_INLINE_BITFIELD(NominalTypeDecl, GenericTypeDecl, 1+1+1,
+  SWIFT_INLINE_BITFIELD(NominalTypeDecl, GenericTypeDecl, 1+1,
     /// Whether we have already added implicitly-defined initializers
     /// to this declaration.
     AddedImplicitInitializers : 1,
 
     /// Whether there is are lazily-loaded conformances for this nominal type.
-    HasLazyConformances : 1,
-
-    /// Whether we have already validated all members of the type that
-    /// affect layout.
-    HasValidatedLayout : 1
+    HasLazyConformances : 1
   );
 
   SWIFT_INLINE_BITFIELD_FULL(ProtocolDecl, NominalTypeDecl, 1+1+1+1+1+1+1+1+2+8+16,
@@ -3036,7 +3032,6 @@ class NominalTypeDecl : public GenericTypeDecl, public IterableDeclContext {
     Bits.NominalTypeDecl.AddedImplicitInitializers = false;
     ExtensionGeneration = 0;
     Bits.NominalTypeDecl.HasLazyConformances = false;
-    Bits.NominalTypeDecl.HasValidatedLayout = false;
   }
 
   friend class ProtocolType;
@@ -3074,18 +3069,6 @@ class NominalTypeDecl : public GenericTypeDecl, public IterableDeclContext {
     Bits.NominalTypeDecl.AddedImplicitInitializers = true;
   }
 
-  /// Determine whether we have already validated any members
-  /// which affect layout.
-  bool hasValidatedLayout() const {
-    return Bits.NominalTypeDecl.HasValidatedLayout;
-  }
-
-  /// Note that we have attempted to validate any members
-  /// which affect layout.
-  void setHasValidatedLayout() {
-    Bits.NominalTypeDecl.HasValidatedLayout = true;
-  }
-
   /// Set the interface type of this nominal type to the metatype of the
   /// declared interface type.
   void computeType();

lib/Sema/TypeCheckDecl.cpp

@@ -2723,7 +2723,6 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
 
     checkUnsupportedNestedType(ED);
     TC.validateDecl(ED);
-    ED->setHasValidatedLayout();
 
     {
       // Check for circular inheritance of the raw type.
@@ -2761,7 +2760,6 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     checkUnsupportedNestedType(SD);
 
     TC.validateDecl(SD);
-    SD->setHasValidatedLayout();
 
     TC.addImplicitConstructors(SD);
 
@@ -2891,7 +2889,6 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
 
     TC.validateDecl(CD);
     TC.requestSuperclassLayout(CD);
-    CD->setHasValidatedLayout();
 
     {
       // Check for circular inheritance.
@@ -4649,11 +4646,6 @@ void TypeChecker::requestMemberLayout(ValueDecl *member) {
 }
 
 void TypeChecker::requestNominalLayout(NominalTypeDecl *nominalDecl) {
-  if (nominalDecl->hasValidatedLayout())
-    return;
-
-  nominalDecl->setHasValidatedLayout();
-
   if (isa<SourceFile>(nominalDecl->getModuleScopeContext()))
     DeclsToFinalize.insert(nominalDecl);
 }