Reimplement function builders as statement transformations.

include/swift/AST/ASTTypeIDZone.def

@@ -17,7 +17,7 @@
 
 SWIFT_TYPEID(AncestryFlags)
 SWIFT_TYPEID(CtorInitializerKind)
-SWIFT_TYPEID(FunctionBuilderClosurePreCheck)
+SWIFT_TYPEID(FunctionBuilderBodyPreCheck)
 SWIFT_TYPEID(GenericSignature)
 SWIFT_TYPEID(ImplicitMemberAction)
 SWIFT_TYPEID(ParamSpecifier)

include/swift/AST/ASTTypeIDs.h

@@ -28,7 +28,7 @@ class ConstructorDecl;
 class CustomAttr;
 class Decl;
 class EnumDecl;
-enum class FunctionBuilderClosurePreCheck : uint8_t;
+enum class FunctionBuilderBodyPreCheck : uint8_t;
 class GenericParamList;
 class GenericSignature;
 class GenericTypeParamType;

include/swift/AST/Expr.h

@@ -3599,7 +3599,10 @@ class ClosureExpr : public AbstractClosureExpr {
   /// the CaptureListExpr which would normally maintain this sort of
   /// information about captured variables), we need to have some way to access
   /// this information directly on the ClosureExpr.
-  VarDecl *CapturedSelfDecl;
+  ///
+  /// The bit indicates whether this closure has had a function builder
+  /// applied to it.
+  llvm::PointerIntPair<VarDecl *, 1, bool> CapturedSelfDeclAndAppliedBuilder;
 
   /// The location of the "throws", if present.
   SourceLoc ThrowsLoc;
@@ -3624,7 +3627,8 @@ class ClosureExpr : public AbstractClosureExpr {
               unsigned discriminator, DeclContext *parent)
     : AbstractClosureExpr(ExprKind::Closure, Type(), /*Implicit=*/false,
                           discriminator, parent),
-      BracketRange(bracketRange), CapturedSelfDecl(capturedSelfDecl),
+      BracketRange(bracketRange),
+      CapturedSelfDeclAndAppliedBuilder(capturedSelfDecl, false),
       ThrowsLoc(throwsLoc), ArrowLoc(arrowLoc), InLoc(inLoc),
       ExplicitResultType(explicitResultType), Body(nullptr) {
     setParameterList(params);
@@ -3726,13 +3730,23 @@ class ClosureExpr : public AbstractClosureExpr {
   bool hasEmptyBody() const;
 
   /// VarDecl captured by this closure under the literal name \c self , if any.
-  VarDecl *getCapturedSelfDecl() const { return CapturedSelfDecl; }
+  VarDecl *getCapturedSelfDecl() const {
+    return CapturedSelfDeclAndAppliedBuilder.getPointer();
+  }
 
   /// Whether this closure captures the \c self param in its body in such a
   /// way that implicit \c self is enabled within its body (i.e. \c self is
   /// captured non-weakly).
   bool capturesSelfEnablingImplictSelf() const;
 
+  bool hasAppliedFunctionBuilder() const {
+    return CapturedSelfDeclAndAppliedBuilder.getInt();
+  }
+
+  void setAppliedFunctionBuilder(bool flag = true) {
+    CapturedSelfDeclAndAppliedBuilder.setInt(flag);
+  }
+
   static bool classof(const Expr *E) {
     return E->getKind() == ExprKind::Closure;
   }

include/swift/AST/TypeCheckRequests.h

@@ -1750,7 +1750,7 @@ class ValueWitnessRequest
   void cacheResult(Witness value) const;
 };
 
-enum class FunctionBuilderClosurePreCheck : uint8_t {
+enum class FunctionBuilderBodyPreCheck : uint8_t {
   /// There were no problems pre-checking the closure.
   Okay,
 
@@ -1763,7 +1763,7 @@ enum class FunctionBuilderClosurePreCheck : uint8_t {
 
 class PreCheckFunctionBuilderRequest
     : public SimpleRequest<PreCheckFunctionBuilderRequest,
-                           FunctionBuilderClosurePreCheck(AnyFunctionRef),
+                           FunctionBuilderBodyPreCheck(AnyFunctionRef),
                            CacheKind::Cached> {
 public:
   using SimpleRequest::SimpleRequest;
@@ -1772,7 +1772,7 @@ class PreCheckFunctionBuilderRequest
   friend SimpleRequest;
 
   // Evaluation.
-  llvm::Expected<FunctionBuilderClosurePreCheck>
+  llvm::Expected<FunctionBuilderBodyPreCheck>
   evaluate(Evaluator &evaluator, AnyFunctionRef fn) const;
 
 public:
@@ -2044,7 +2044,7 @@ AnyValue::Holder<GenericSignature>::equals(const HolderBase &other) const {
 void simple_display(llvm::raw_ostream &out, Type value);
 void simple_display(llvm::raw_ostream &out, const TypeRepr *TyR);
 void simple_display(llvm::raw_ostream &out, ImplicitMemberAction action);
-void simple_display(llvm::raw_ostream &out, FunctionBuilderClosurePreCheck pck);
+void simple_display(llvm::raw_ostream &out, FunctionBuilderBodyPreCheck pck);
 
 #define SWIFT_TYPEID_ZONE TypeChecker
 #define SWIFT_TYPEID_HEADER "swift/AST/TypeCheckerTypeIDZone.def"

lib/AST/TypeCheckRequests.cpp

@@ -1122,15 +1122,15 @@ void ValueWitnessRequest::cacheResult(Witness type) const {
 //----------------------------------------------------------------------------//
 
 void swift::simple_display(llvm::raw_ostream &out,
-                           FunctionBuilderClosurePreCheck value) {
+                           FunctionBuilderBodyPreCheck value) {
   switch (value) {
-  case FunctionBuilderClosurePreCheck::Okay:
+  case FunctionBuilderBodyPreCheck::Okay:
     out << "okay";
     break;
-  case FunctionBuilderClosurePreCheck::HasReturnStmt:
+  case FunctionBuilderBodyPreCheck::HasReturnStmt:
     out << "has return statement";
     break;
-  case FunctionBuilderClosurePreCheck::Error:
+  case FunctionBuilderBodyPreCheck::Error:
     out << "error";
     break;
   }