AST: Rework AbstractFunctionDecl construction away from multiple parameter lists

There are two general constructor forms here:

- One took the number of parameter lists, to be filled in later.
  Now, this takes a boolean indicating if there is an implicit
  'self'.

- The other one took the actual parameter lists and filled them
  in right away. This now takes a separate 'self' ParamDecl and
  ParameterList.

Instead of storing the number of parameter lists, an
AbstractFunctionDecl now only needs to store if there is a 'self'
or not.

I've updated most places that construct AbstractFunctionDecls to
properly use these new forms. In the ClangImporter, there is
more code that remains to be untangled, so we continue to build
multiple ParameterLists and unpack them into a ParamDecl and
ParameterList at the last minute.

Author: slavapestov

include/swift/AST/Decl.h

@@ -380,15 +380,15 @@ class alignas(1 << DeclAlignInBits) Decl {
     DefaultArgumentResilienceExpansion : 1
   );
 
-  SWIFT_INLINE_BITFIELD(AbstractFunctionDecl, ValueDecl, 3+8+5+1+1+1+1+1+1,
+  SWIFT_INLINE_BITFIELD(AbstractFunctionDecl, ValueDecl, 3+8+1+1+1+1+1+1+1,
     /// \see AbstractFunctionDecl::BodyKind
     BodyKind : 3,
 
     /// Import as member status.
     IAMStatus : 8,
 
-    /// Number of curried parameter lists.
-    NumParameterLists : 5,
+    /// Whether the function has an implicit 'self' parameter.
+    HasImplicitSelfDecl : 1,
 
     /// Whether we are overridden later.
     Overridden : 1,
@@ -5001,24 +5001,21 @@ class AbstractFunctionDecl : public GenericContext, public ValueDecl {
 
   AbstractFunctionDecl(DeclKind Kind, DeclContext *Parent, DeclName Name,
                        SourceLoc NameLoc, bool Throws, SourceLoc ThrowsLoc,
-                       unsigned NumParameterLists,
+                       bool HasImplicitSelfDecl,
                        GenericParamList *GenericParams)
       : GenericContext(DeclContextKind::AbstractFunctionDecl, Parent),
         ValueDecl(Kind, Parent, Name, NameLoc),
         Body(nullptr), ThrowsLoc(ThrowsLoc) {
     setBodyKind(BodyKind::None);
     setGenericParams(GenericParams);
-    Bits.AbstractFunctionDecl.NumParameterLists = NumParameterLists;
+    Bits.AbstractFunctionDecl.HasImplicitSelfDecl = HasImplicitSelfDecl;
     Bits.AbstractFunctionDecl.Overridden = false;
     Bits.AbstractFunctionDecl.Throws = Throws;
     Bits.AbstractFunctionDecl.NeedsNewVTableEntry = false;
     Bits.AbstractFunctionDecl.HasComputedNeedsNewVTableEntry = false;
     Bits.AbstractFunctionDecl.DefaultArgumentResilienceExpansion =
         unsigned(ResilienceExpansion::Maximal);
     Bits.AbstractFunctionDecl.Synthesized = false;
-
-    // Verify no bitfield truncation.
-    assert(Bits.AbstractFunctionDecl.NumParameterLists == NumParameterLists);
   }
 
   void setBodyKind(BodyKind K) {
@@ -5064,7 +5061,6 @@ class AbstractFunctionDecl : public GenericContext, public ValueDecl {
     Bits.AbstractFunctionDecl.IAMStatus = newValue.getRawValue();
   }
 
-public:
   /// Retrieve the location of the 'throws' keyword, if present.
   SourceLoc getThrowsLoc() const { return ThrowsLoc; }
 
@@ -5200,7 +5196,7 @@ class AbstractFunctionDecl : public GenericContext, public ValueDecl {
   /// function.  This value is one for free-standing functions, and two for
   /// methods.
   unsigned getNumParameterLists() const {
-    return Bits.AbstractFunctionDecl.NumParameterLists;
+    return Bits.AbstractFunctionDecl.HasImplicitSelfDecl ? 2 : 1;
   }
 
   /// \brief Returns the parameter pattern(s) for the function definition that
@@ -5227,6 +5223,9 @@ class AbstractFunctionDecl : public GenericContext, public ValueDecl {
     return getParameterLists().back();
   }
 
+  void setParameters(ParamDecl *SelfDecl,
+                     ParameterList *Params);
+
   /// \brief This method returns the implicit 'self' decl.
   ///
   /// Note that some functions don't have an implicit 'self' decl, for example,
@@ -5341,19 +5340,18 @@ class FuncDecl : public AbstractFunctionDecl {
            SourceLoc FuncLoc,
            DeclName Name, SourceLoc NameLoc,
            bool Throws, SourceLoc ThrowsLoc,
-           unsigned NumParameterLists,
+           bool HasImplicitSelfDecl,
            GenericParamList *GenericParams, DeclContext *Parent)
     : AbstractFunctionDecl(Kind, Parent,
                            Name, NameLoc,
                            Throws, ThrowsLoc,
-                           NumParameterLists, GenericParams),
+                           HasImplicitSelfDecl, GenericParams),
       StaticLoc(StaticLoc), FuncLoc(FuncLoc) {
     assert(!Name.getBaseName().isSpecial());
 
     Bits.FuncDecl.IsStatic =
       StaticLoc.isValid() || StaticSpelling != StaticSpellingKind::None;
     Bits.FuncDecl.StaticSpelling = static_cast<unsigned>(StaticSpelling);
-    assert(NumParameterLists > 0 && "Must have at least an empty tuple arg");
 
     Bits.FuncDecl.HasDynamicSelf = false;
     Bits.FuncDecl.ForcedStaticDispatch = false;
@@ -5367,7 +5365,7 @@ class FuncDecl : public AbstractFunctionDecl {
                               DeclName Name, SourceLoc NameLoc,
                               bool Throws, SourceLoc ThrowsLoc,
                               GenericParamList *GenericParams,
-                              unsigned NumParameterLists,
+                              bool HasImplicitSelfDecl,
                               DeclContext *Parent,
                               ClangNode ClangN);
 
@@ -5379,7 +5377,7 @@ class FuncDecl : public AbstractFunctionDecl {
                                       DeclName Name, SourceLoc NameLoc,
                                       bool Throws, SourceLoc ThrowsLoc,
                                       GenericParamList *GenericParams,
-                                      unsigned NumParameterLists,
+                                      bool HasImplicitSelfDecl,
                                       DeclContext *Parent);
 
   static FuncDecl *create(ASTContext &Context, SourceLoc StaticLoc,
@@ -5388,7 +5386,8 @@ class FuncDecl : public AbstractFunctionDecl {
                           DeclName Name, SourceLoc NameLoc,
                           bool Throws, SourceLoc ThrowsLoc,
                           GenericParamList *GenericParams,
-                          ArrayRef<ParameterList *> ParameterLists,
+                          ParamDecl *SelfDecl,
+                          ParameterList *ParameterList,
                           TypeLoc FnRetType, DeclContext *Parent,
                           ClangNode ClangN = ClangNode());
 
@@ -5455,9 +5454,6 @@ class FuncDecl : public AbstractFunctionDecl {
   /// attribute. For example a "mutating set" accessor.
   bool isExplicitNonMutating() const;
 
-  void setDeserializedSignature(ArrayRef<ParameterList *> ParameterLists,
-                                TypeLoc FnRetType);
-
   SourceLoc getStaticLoc() const { return StaticLoc; }
   SourceLoc getFuncLoc() const { return FuncLoc; }
 
@@ -5594,7 +5590,7 @@ class AccessorDecl final : public FuncDecl {
                                   SourceLoc staticLoc,
                                   StaticSpellingKind staticSpelling,
                                   bool throws, SourceLoc throwsLoc,
-                                  unsigned numParameterLists,
+                                  bool hasImplicitSelfDecl,
                                   GenericParamList *genericParams,
                                   DeclContext *parent,
                                   ClangNode clangNode);
@@ -5610,7 +5606,7 @@ class AccessorDecl final : public FuncDecl {
                               StaticSpellingKind staticSpelling,
                               bool throws, SourceLoc throwsLoc,
                               GenericParamList *genericParams,
-                              unsigned numParameterLists,
+                              bool hasImplicitSelfDecl,
                               DeclContext *parent);
 
   static AccessorDecl *create(ASTContext &ctx, SourceLoc declLoc,
@@ -5622,7 +5618,8 @@ class AccessorDecl final : public FuncDecl {
                               StaticSpellingKind staticSpelling,
                               bool throws, SourceLoc throwsLoc,
                               GenericParamList *genericParams,
-                              ArrayRef<ParameterList *> parameterLists,
+                              ParamDecl *selfDecl,
+                              ParameterList *parameterList,
                               TypeLoc fnRetType, DeclContext *parent,
                               ClangNode clangNode = ClangNode());
 
@@ -5923,8 +5920,6 @@ class ConstructorDecl : public AbstractFunctionDecl {
                   GenericParamList *GenericParams, 
                   DeclContext *Parent);
 
-  void setParameterLists(ParamDecl *selfParam, ParameterList *bodyParams);
-
   SourceLoc getConstructorLoc() const { return getNameLoc(); }
   SourceLoc getStartLoc() const { return getConstructorLoc(); }
   SourceRange getSourceRange() const;
@@ -6114,8 +6109,6 @@ class DestructorDecl : public AbstractFunctionDecl {
   DestructorDecl(SourceLoc DestructorLoc, ParamDecl *selfDecl,
                  DeclContext *Parent);
 
-  void setSelfDecl(ParamDecl *selfDecl);
-
   MutableArrayRef<ParameterList *> getParameterLists() {
     return { ParameterLists, 2 };
   }

include/swift/AST/ParameterList.h

@@ -65,25 +65,6 @@ class alignas(ParamDecl *) ParameterList final :
   static ParameterList *createWithoutLoc(ParamDecl *decl) {
     return create(decl->getASTContext(), decl);
   }
-  
-  /// Create an implicit 'self' decl for a method in the specified decl context.
-  /// If 'static' is true, then this is self for a static method in the type.
-  ///
-  /// Note that this decl is created, but it is returned with an incorrect
-  /// DeclContext that needs to be set correctly.  This is automatically handled
-  /// when a function is created with this as part of its argument list.
-  ///
-  static ParameterList *createUnboundSelf(SourceLoc loc, DeclContext *DC);
-
-  /// Create an implicit 'self' decl for a method in the specified decl context.
-  /// If 'static' is true, then this is self for a static method in the type.
-  ///
-  /// Note that this decl is created, but it is returned with an incorrect
-  /// DeclContext that needs to be set correctly.  This is automatically handled
-  /// when a function is created with this as part of its argument list.
-  static ParameterList *createSelf(SourceLoc loc, DeclContext *DC,
-                                   bool isStatic = false,
-                                   bool isInOut = false);
 
   SourceLoc getLParenLoc() const { return LParenLoc; }
   SourceLoc getRParenLoc() const { return RParenLoc; }

include/swift/Parse/Parser.h

@@ -1102,12 +1102,12 @@ class Parser {
                           DefaultArgumentInfo *defaultArgs = nullptr);
 
   ParserStatus parseFunctionArguments(SmallVectorImpl<Identifier> &NamePieces,
-                                    SmallVectorImpl<ParameterList*> &BodyParams,
+                                      ParameterList *&BodyParams,
                                       ParameterContextKind paramContext,
                                       DefaultArgumentInfo &defaultArgs);
   ParserStatus parseFunctionSignature(Identifier functionName,
                                       DeclName &fullName,
-                              SmallVectorImpl<ParameterList *> &bodyParams,
+                                      ParameterList *&bodyParams,
                                       DefaultArgumentInfo &defaultArgs,
                                       SourceLoc &throws,
                                       bool &rethrows,

lib/AST/Builtins.cpp

@@ -178,6 +178,7 @@ getBuiltinFunction(Identifier Id, ArrayRef<Type> argTypes, Type ResType,
                              Name, /*NameLoc=*/SourceLoc(),
                              /*Throws=*/false, /*ThrowsLoc=*/SourceLoc(),
                              /*GenericParams=*/nullptr,
+                             /*SelfDecl=*/nullptr,
                              paramList,
                              TypeLoc::withoutLoc(ResType), DC);
   FD->setInterfaceType(FnType);
@@ -242,7 +243,9 @@ getBuiltinGenericFunction(Identifier Id,
                                /*FuncLoc=*/SourceLoc(),
                                Name, /*NameLoc=*/SourceLoc(),
                                /*Throws=*/false, /*ThrowsLoc=*/SourceLoc(),
-                               GenericParams, paramList,
+                               GenericParams,
+                               /*SelfDecl=*/nullptr,
+                               paramList,
                                TypeLoc::withoutLoc(ResBodyType), DC);
 
   func->setInterfaceType(InterfaceType);