2 files changed, 34 insertions, 22 deletions

diff --git a/clang/include/clang/AST/DeclTemplate.h b/clang/include/clang/AST/DeclTemplate.h
index a9109ef1142..7e6dfbba27c 100644
--- a/clang/include/clang/AST/DeclTemplate.h
+++ b/clang/include/clang/AST/DeclTemplate.h
@@ -332,24 +332,23 @@ class TemplateDecl : public NamedDecl {
   void anchor() override;
 protected:
   // This is probably never used.
-  TemplateDecl(Kind DK, DeclContext *DC, SourceLocation L,
-               DeclarationName Name)
-    : NamedDecl(DK, DC, L, Name), TemplatedDecl(nullptr),
-      TemplateParams(nullptr) {}
+  TemplateDecl(Kind DK, DeclContext *DC, SourceLocation L, DeclarationName Name)
+      : NamedDecl(DK, DC, L, Name), TemplatedDecl(nullptr, false),
+        TemplateParams(nullptr) {}
 
   // Construct a template decl with the given name and parameters.
   // Used when there is not templated element (tt-params).
-  TemplateDecl(Kind DK, DeclContext *DC, SourceLocation L,
-               DeclarationName Name, TemplateParameterList *Params)
-    : NamedDecl(DK, DC, L, Name), TemplatedDecl(nullptr),
-      TemplateParams(Params) {}
+  TemplateDecl(Kind DK, DeclContext *DC, SourceLocation L, DeclarationName Name,
+               TemplateParameterList *Params)
+      : NamedDecl(DK, DC, L, Name), TemplatedDecl(nullptr, false),
+        TemplateParams(Params) {}
 
   // Construct a template decl with name, parameters, and templated element.
-  TemplateDecl(Kind DK, DeclContext *DC, SourceLocation L,
-               DeclarationName Name, TemplateParameterList *Params,
-               NamedDecl *Decl)
-    : NamedDecl(DK, DC, L, Name), TemplatedDecl(Decl),
-      TemplateParams(Params) { }
+  TemplateDecl(Kind DK, DeclContext *DC, SourceLocation L, DeclarationName Name,
+               TemplateParameterList *Params, NamedDecl *Decl)
+      : NamedDecl(DK, DC, L, Name), TemplatedDecl(Decl, false),
+        TemplateParams(Params) {}
+
 public:
   /// Get the list of template parameters
   TemplateParameterList *getTemplateParameters() const {
@@ -357,7 +356,7 @@ public:
   }
 
   /// Get the underlying, templated declaration.
-  NamedDecl *getTemplatedDecl() const { return TemplatedDecl; }
+  NamedDecl *getTemplatedDecl() const { return TemplatedDecl.getPointer(); }
 
   // Implement isa/cast/dyncast/etc.
   static bool classof(const Decl *D) { return classofKind(D->getKind()); }
@@ -367,20 +366,30 @@ public:
 
   SourceRange getSourceRange() const override LLVM_READONLY {
     return SourceRange(TemplateParams->getTemplateLoc(),
-                       TemplatedDecl->getSourceRange().getEnd());
+                       TemplatedDecl.getPointer()->getSourceRange().getEnd());
   }
 
+  /// Whether this is a (C++ Concepts TS) function or variable concept.
+  bool isConcept() const { return TemplatedDecl.getInt(); }
+  void setConcept() { TemplatedDecl.setInt(true); }
+
 protected:
-  NamedDecl *TemplatedDecl;
+  /// \brief The named declaration from which this template was instantiated.
+  /// (or null).
+  ///
+  /// The boolean value will be true to indicate that this template
+  /// (function or variable) is a concept.
+  llvm::PointerIntPair<NamedDecl *, 1, bool> TemplatedDecl;
+
   TemplateParameterList* TemplateParams;
 
 public:
   /// \brief Initialize the underlying templated declaration and
   /// template parameters.
   void init(NamedDecl *templatedDecl, TemplateParameterList* templateParams) {
-    assert(!TemplatedDecl && "TemplatedDecl already set!");
+    assert(!TemplatedDecl.getPointer() && "TemplatedDecl already set!");
     assert(!TemplateParams && "TemplateParams already set!");
-    TemplatedDecl = templatedDecl;
+    TemplatedDecl.setPointer(templatedDecl);
     TemplateParams = templateParams;
   }
 };
@@ -889,7 +898,7 @@ public:
 
   /// Get the underlying function declaration of the template.
   FunctionDecl *getTemplatedDecl() const {
-    return static_cast<FunctionDecl*>(TemplatedDecl);
+    return static_cast<FunctionDecl *>(TemplatedDecl.getPointer());
   }
 
   /// Returns whether this template declaration defines the primary
@@ -1982,7 +1991,7 @@ public:
 
   /// \brief Get the underlying class declarations of the template.
   CXXRecordDecl *getTemplatedDecl() const {
-    return static_cast<CXXRecordDecl *>(TemplatedDecl);
+    return static_cast<CXXRecordDecl *>(TemplatedDecl.getPointer());
   }
 
   /// \brief Returns whether this template declaration defines the primary
@@ -2245,7 +2254,7 @@ protected:
 public:
   /// Get the underlying function declaration of the template.
   TypeAliasDecl *getTemplatedDecl() const {
-    return static_cast<TypeAliasDecl*>(TemplatedDecl);
+    return static_cast<TypeAliasDecl *>(TemplatedDecl.getPointer());
   }
 
 
@@ -2808,7 +2817,7 @@ public:
 
   /// \brief Get the underlying variable declarations of the template.
   VarDecl *getTemplatedDecl() const {
-    return static_cast<VarDecl *>(TemplatedDecl);
+    return static_cast<VarDecl *>(TemplatedDecl.getPointer());
   }
 
   /// \brief Returns whether this template declaration defines the primary
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index f176344486a..ca0d3834cd1 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2080,6 +2080,9 @@ def err_function_concept_bool_ret : Error<
   "declared return type of function concept must be 'bool'">;
 def err_variable_concept_bool_decl : Error<
   "declared type of variable concept must be 'bool'">;
+def err_concept_specified_specialization : Error<
+  "'concept' cannot be applied on an "
+  "%select{explicit instantiation|explicit specialization|partial specialization}0">;
 
 // C++11 char16_t/char32_t
 def warn_cxx98_compat_unicode_type : Warning<