[AST] Remove trailing pack elements from PackExpansionExpr.

This wasn't used, and callers can instead use getExpandedPacks, which
also includes TypeReprs.

Author: hborla

include/swift/AST/Expr.h

@@ -350,11 +350,6 @@ class alignas(8) Expr : public ASTAllocated<Expr> {
     IsObjC : 1
   );
 
-  SWIFT_INLINE_BITFIELD_FULL(PackExpansionExpr, Expr, 32,
-    : NumPadBits,
-    NumBindings : 32
-  );
-
   SWIFT_INLINE_BITFIELD_FULL(SequenceExpr, Expr, 32,
     : NumPadBits,
     NumElements : 32
@@ -3599,38 +3594,21 @@ class PackElementExpr final : public Expr {
 /// that naturally accept a comma-separated list of values, including
 /// call argument lists, the elements of a tuple value, and the source
 /// of a for-in loop.
-class PackExpansionExpr final : public Expr,
-    private llvm::TrailingObjects<PackExpansionExpr, PackElementExpr *> {
-  friend TrailingObjects;
-
+class PackExpansionExpr final : public Expr {
   Expr *PatternExpr;
   SourceLoc DotsLoc;
   GenericEnvironment *Environment;
 
   PackExpansionExpr(Expr *patternExpr,
-                    ArrayRef<PackElementExpr *> packElements,
                     SourceLoc dotsLoc,
                     GenericEnvironment *environment,
                     bool implicit, Type type)
     : Expr(ExprKind::PackExpansion, implicit, type),
-      PatternExpr(patternExpr), DotsLoc(dotsLoc), Environment(environment) {
-    Bits.PackExpansionExpr.NumBindings = packElements.size();
-    std::uninitialized_copy(packElements.begin(), packElements.end(),
-                            getTrailingObjects<PackElementExpr *>());
-  }
-
-  size_t numTrailingObjects(OverloadToken<PackElementExpr *>) const {
-    return getNumBindings();
-  }
-
-  MutableArrayRef<PackElementExpr *> getMutableBindings() {
-    return {getTrailingObjects<PackElementExpr *>(), getNumBindings()};
-  }
+      PatternExpr(patternExpr), DotsLoc(dotsLoc), Environment(environment) {}
 
 public:
   static PackExpansionExpr *create(ASTContext &ctx,
                                    Expr *patternExpr,
-                                   ArrayRef<PackElementExpr *> packElements,
                                    SourceLoc dotsLoc,
                                    GenericEnvironment *environment,
                                    bool implicit = false,
@@ -3642,14 +3620,6 @@ class PackExpansionExpr final : public Expr,
     PatternExpr = patternExpr;
   }
 
-  unsigned getNumBindings() const {
-    return Bits.PackExpansionExpr.NumBindings;
-  }
-
-  ArrayRef<PackElementExpr *> getPackElements() {
-    return {getTrailingObjects<PackElementExpr *>(), getNumBindings()};
-  }
-
   void getExpandedPacks(SmallVectorImpl<ASTNode> &packs);
 
   GenericEnvironment *getGenericEnvironment() {

lib/AST/Expr.cpp

@@ -1251,15 +1251,10 @@ VarargExpansionExpr *VarargExpansionExpr::createArrayExpansion(ASTContext &ctx,
 
 PackExpansionExpr *
 PackExpansionExpr::create(ASTContext &ctx, Expr *patternExpr,
-                          ArrayRef<PackElementExpr *> packElements,
                           SourceLoc dotsLoc, GenericEnvironment *environment,
                           bool implicit, Type type) {
-  size_t size =
-      totalSizeToAlloc<PackElementExpr *>(packElements.size());
-  void *mem = ctx.Allocate(size, alignof(PackExpansionExpr));
-  return ::new (mem) PackExpansionExpr(patternExpr, packElements,
-                                       dotsLoc, environment,
-                                       implicit, type);
+  return new (ctx) PackExpansionExpr(patternExpr, dotsLoc, environment,
+                                     implicit, type);
 }
 
 void PackExpansionExpr::getExpandedPacks(SmallVectorImpl<ASTNode> &packs) {

lib/Sema/PreCheckExpr.cpp

@@ -406,7 +406,6 @@ static Expr *getPackExpansion(DeclContext *dc, Expr *expr, SourceLoc opLoc) {
   // PackElementOf constraints.
   struct PackReferenceFinder : public ASTWalker {
     DeclContext *dc;
-    llvm::SmallVector<PackElementExpr *, 2> packElements;
     GenericEnvironment *environment;
 
     PackReferenceFinder(DeclContext *dc)
@@ -431,7 +430,6 @@ static Expr *getPackExpansion(DeclContext *dc, Expr *expr, SourceLoc opLoc) {
         return Action::Continue(E);
 
       createElementEnvironment();
-      packElements.push_back(packElement);
       return Action::Continue(packElement);
     }
 
@@ -448,7 +446,6 @@ static Expr *getPackExpansion(DeclContext *dc, Expr *expr, SourceLoc opLoc) {
 
   if (packReferenceFinder.environment != nullptr) {
     return PackExpansionExpr::create(dc->getASTContext(), pattern,
-                                     packReferenceFinder.packElements,
                                      opLoc, packReferenceFinder.environment);
   }