[AST] NFC: Introduce PatternBindingInitializer::create

Author: hamishknight

include/swift/AST/Initializer.h

@@ -84,13 +84,16 @@ class PatternBindingInitializer : public Initializer {
     SelfParam = nullptr;
   }
 
-public:
   explicit PatternBindingInitializer(DeclContext *parent)
     : Initializer(InitializerKind::PatternBinding, parent),
       Binding(nullptr), SelfParam(nullptr) {
     SpareBits = 0;
   }
- 
+
+public:
+  static PatternBindingInitializer *create(DeclContext *parent) {
+    return new (parent->getASTContext()) PatternBindingInitializer(parent);
+  }
 
   void setBinding(PatternBindingDecl *binding, unsigned bindingIndex) {
     setParent(binding->getDeclContext());

lib/AST/ASTBridging.cpp

@@ -343,8 +343,7 @@ bool BridgedDeclContext_isLocalContext(BridgedDeclContext cDeclContext) {
 
 BridgedPatternBindingInitializer
 BridgedPatternBindingInitializer_create(BridgedDeclContext cDeclContext) {
-  auto *dc = cDeclContext.unbridged();
-  return new (dc->getASTContext()) PatternBindingInitializer(dc);
+  return PatternBindingInitializer::create(cDeclContext.unbridged());
 }
 
 BridgedDeclContext BridgedPatternBindingInitializer_asDeclContext(

lib/AST/Decl.cpp

@@ -1931,7 +1931,7 @@ PatternBindingDecl::create(ASTContext &Ctx, SourceLoc StaticLoc,
     // closures/decls present in the initialization expr. This currently should
     // only affect implicit code though.
     if (!initContext && !Parent->isLocalContext())
-      initContext = new (Ctx) PatternBindingInitializer(Parent);
+      initContext = PatternBindingInitializer::create(Parent);
 
     if (initContext)
       initContext->setBinding(PBD, idx);

lib/Parse/ParseDecl.cpp

@@ -4173,10 +4173,8 @@ ParserResult<CustomAttr> Parser::parseCustomAttribute(
       // initializers.
       llvm::Optional<ParseFunctionBody> initParser;
       if (!CurDeclContext->isLocalContext()) {
-        if (!initContext) {
-          initContext =
-              new (Context) PatternBindingInitializer(CurDeclContext);
-        }
+        if (!initContext)
+          initContext = PatternBindingInitializer::create(CurDeclContext);
 
         initParser.emplace(*this, initContext);
       }
@@ -8339,7 +8337,7 @@ Parser::parseDeclVar(ParseDeclOptions Flags,
       // for the PBD we'll eventually create.  This allows us to have reasonable
       // DeclContexts for any closures that may live inside of initializers.
       if (!CurDeclContext->isLocalContext() && !topLevelDecl && !initContext)
-        initContext = new (Context) PatternBindingInitializer(CurDeclContext);
+        initContext = PatternBindingInitializer::create(CurDeclContext);
 
       // If we're using a local context (either a TopLevelCodeDecl or a
       // PatternBindingContext) install it now so that CurDeclContext is set