1 files changed, 27 insertions, 50 deletions

diff --git a/clang/include/clang/AST/DeclTemplate.h b/clang/include/clang/AST/DeclTemplate.h
index e70b29e53a2..10ec5aa9fce 100644
--- a/clang/include/clang/AST/DeclTemplate.h
+++ b/clang/include/clang/AST/DeclTemplate.h
@@ -46,8 +46,7 @@ typedef llvm::PointerUnion3<TemplateTypeParmDecl*, NonTypeTemplateParmDecl*,
 /// \brief Stores a list of template parameters for a TemplateDecl and its
 /// derived classes.
 class TemplateParameterList final
-    : private llvm::TrailingObjects<TemplateParameterList, NamedDecl *,
-                                    Expr *> {
+    : private llvm::TrailingObjects<TemplateParameterList, NamedDecl *> {
 
   /// The location of the 'template' keyword.
   SourceLocation TemplateLoc;
@@ -57,36 +56,26 @@ class TemplateParameterList final
 
   /// The number of template parameters in this template
   /// parameter list.
-  unsigned NumParams : 30;
+  unsigned NumParams : 31;
 
   /// Whether this template parameter list contains an unexpanded parameter
   /// pack.
   unsigned ContainsUnexpandedParameterPack : 1;
 
-  /// Whether this template parameter list has an associated requires-clause
-  unsigned HasRequiresClause : 1;
-
 protected:
   size_t numTrailingObjects(OverloadToken<NamedDecl *>) const {
     return NumParams;
   }
 
-  size_t numTrailingObjects(OverloadToken<Expr *>) const {
-    return HasRequiresClause;
-  }
-
   TemplateParameterList(SourceLocation TemplateLoc, SourceLocation LAngleLoc,
-                        ArrayRef<NamedDecl *> Params, SourceLocation RAngleLoc,
-                        Expr *RequiresClause);
+                        ArrayRef<NamedDecl *> Params, SourceLocation RAngleLoc);
 
 public:
-  // FIXME: remove default argument for RequiresClause
   static TemplateParameterList *Create(const ASTContext &C,
                                        SourceLocation TemplateLoc,
                                        SourceLocation LAngleLoc,
                                        ArrayRef<NamedDecl *> Params,
-                                       SourceLocation RAngleLoc,
-                                       Expr *RequiresClause = nullptr);
+                                       SourceLocation RAngleLoc);
 
   /// \brief Iterates through the template parameters in this list.
   typedef NamedDecl** iterator;
@@ -138,16 +127,6 @@ public:
     return ContainsUnexpandedParameterPack;
   }
 
-  /// \brief The constraint-expression of the associated requires-clause.
-  Expr *getRequiresClause() {
-    return HasRequiresClause ? *getTrailingObjects<Expr *>() : nullptr;
-  }
-
-  /// \brief The constraint-expression of the associated requires-clause.
-  const Expr *getRequiresClause() const {
-    return HasRequiresClause ? *getTrailingObjects<Expr *>() : nullptr;
-  }
-
   SourceLocation getTemplateLoc() const { return TemplateLoc; }
   SourceLocation getLAngleLoc() const { return LAngleLoc; }
   SourceLocation getRAngleLoc() const { return RAngleLoc; }
@@ -157,33 +136,36 @@ public:
   }
 
   friend TrailingObjects;
-
-  template <size_t N, bool HasRequiresClause>
-  friend class FixedSizeTemplateParameterListStorage;
+  template <size_t N> friend class FixedSizeTemplateParameterListStorage;
 };
 
-/// \brief Stores a list of template parameters and the associated
-/// requires-clause (if any) for a TemplateDecl and its derived classes.
-/// Suitable for creating on the stack.
-template <size_t N, bool HasRequiresClause>
-class FixedSizeTemplateParameterListStorage
-    : public TemplateParameterList::FixedSizeStorageOwner {
-  typename TemplateParameterList::FixedSizeStorage<
-      NamedDecl *, Expr *>::with_counts<
-      N, HasRequiresClause ? 1u : 0u
-      >::type storage;
+/// \brief Stores a list of template parameters for a TemplateDecl and its
+/// derived classes. Suitable for creating on the stack.
+template <size_t N> class FixedSizeTemplateParameterListStorage {
+  // This is kinda ugly: TemplateParameterList usually gets allocated
+  // in a block of memory with NamedDecls appended to it. Here, to get
+  // it stack allocated, we include the params as a separate
+  // variable. After allocation, the TemplateParameterList object
+  // treats them as part of itself.
+  TemplateParameterList List;
+  NamedDecl *Params[N];
 
 public:
   FixedSizeTemplateParameterListStorage(SourceLocation TemplateLoc,
                                         SourceLocation LAngleLoc,
                                         ArrayRef<NamedDecl *> Params,
-                                        SourceLocation RAngleLoc,
-                                        Expr *RequiresClause)
-      : FixedSizeStorageOwner(
-            (assert(N == Params.size()),
-             assert(HasRequiresClause == static_cast<bool>(RequiresClause)),
-             new (static_cast<void *>(&storage)) TemplateParameterList(
-                 TemplateLoc, LAngleLoc, Params, RAngleLoc, RequiresClause))) {}
+                                        SourceLocation RAngleLoc)
+      : List(TemplateLoc, LAngleLoc, Params, RAngleLoc) {
+    // Because we're doing an evil layout hack above, have some
+    // asserts, just to double-check everything is laid out like
+    // expected.
+    assert(sizeof(*this) ==
+               TemplateParameterList::totalSizeToAlloc<NamedDecl *>(N) &&
+           "Object layout not as expected");
+    assert(this->Params == List.getTrailingObjects<NamedDecl *>() &&
+           "Object layout not as expected");
+  }
+  TemplateParameterList *get() { return &List; }
 };
 
 /// \brief A template argument list.
@@ -371,11 +353,6 @@ public:
     return TemplateParams;
   }
 
-  /// Get the constraint-expression from the associated requires-clause (if any)
-  const Expr *getRequiresClause() const {
-    return TemplateParams ? TemplateParams->getRequiresClause() : nullptr;
-  }
-
   /// Get the underlying, templated declaration.
   NamedDecl *getTemplatedDecl() const { return TemplatedDecl.getPointer(); }