ahatanak updated this revision to Diff 72356.
ahatanak added a comment.

I agree that extending the logic of getTemplateInstantiationArgs seems like a 
better approach. I changed Sema::getTemplateInstantiationArgs to search for the 
template arguments twice, first for the initializer's template arguments and 
then for the VarTemplateSpecializationDecl. This should enable handling cases 
where a variable template is declared inside a class/struct.

I wonder whether VarTemplateSpecializationDecl can be made a subclass of 
DeclContext and have it contain the lambda class of the initializer. I think 
that will simplify the logic of getTemplateInstantiationArgs.


https://reviews.llvm.org/D23096

Files:
  include/clang/Sema/Sema.h
  lib/Sema/Sema.cpp
  lib/Sema/SemaTemplate.cpp
  lib/Sema/SemaTemplateInstantiate.cpp
  lib/Sema/SemaTemplateInstantiateDecl.cpp
  test/SemaCXX/vartemplate-lambda.cpp
  test/SemaTemplate/default-expr-arguments-3.cpp

Index: test/SemaTemplate/default-expr-arguments-3.cpp
===================================================================
--- /dev/null
+++ test/SemaTemplate/default-expr-arguments-3.cpp
@@ -0,0 +1,52 @@
+// RUN: %clang_cc1 -std=c++14 -ast-dump %s 2>&1 | FileCheck %s
+
+namespace PR28795 {
+  // CHECK: FunctionDecl{{.*}}func 'void (void)'
+  // CHECK:  LambdaExpr
+  // CHECK:   CXXMethodDecl{{.*}}operator() 'enum foo (enum foo) const' inline
+  // CHECK:    ParmVarDecl{{.*}}f 'enum foo' cinit
+  // CHECK:     DeclRefExpr{{.*}}'enum foo' EnumConstant{{.*}}'a' 'enum foo'
+
+  template<typename T>
+  void func() {
+    enum class foo { a, b };
+    auto bar = [](foo f = foo::a) { return f; };
+    bar();
+  }
+
+  void foo() {
+    func<int>();
+  }
+}
+
+// Template struct case:
+
+// CHECK: ClassTemplateSpecializationDecl{{.*}}struct class2 definition
+// CHECK:  LambdaExpr
+// CHECK:   CXXMethodDecl{{.*}}used operator() 'enum foo (enum foo) const' inline
+// CHECK:    ParmVarDecl{{.*}}f 'enum foo' cinit
+// CHECK:     DeclRefExpr{{.*}}'enum foo' EnumConstant{{.*}}'a' 'enum foo'
+
+template <class T> struct class2 {
+  void bar() {
+    enum class foo { a, b };
+    [](foo f = foo::a) { return f; }();
+  }
+};
+
+template struct class2<int>;
+
+// CHECK: FunctionDecl{{.*}}f1 'void (void)'
+// CHECK:  CXXMethodDecl{{.*}}g1 'int (enum foo)'
+// CHECK:   ParmVarDecl{{.*}}n 'enum foo' cinit
+// CHECK:    DeclRefExpr{{.*}}'enum foo' EnumConstant{{.*}}'a' 'enum foo'
+
+template<typename T>
+void f1() {
+  enum class foo { a, b };
+  struct S {
+    int g1(foo n = foo::a);
+  };
+}
+
+template void f1<int>();
Index: test/SemaCXX/vartemplate-lambda.cpp
===================================================================
--- test/SemaCXX/vartemplate-lambda.cpp
+++ test/SemaCXX/vartemplate-lambda.cpp
@@ -1,15 +1,22 @@
 // RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify %s
-// expected-no-diagnostics
 
 template <class> auto fn0 = [] {};
 template <typename> void foo0() { fn0<char>(); }
 
 template<typename T> auto fn1 = [](auto a) { return a + T(1); };
+template<typename T> auto v1 = [](int a = T(1)) { return a; }();
+
+struct S {
+  template<class T>
+  static constexpr T t = [](int f = T(7)){return f;}(); // expected-error{{constexpr variable 't<int>' must be initialized by a constant expression}} expected-error{{a lambda expression may not appear inside of a constant expression}} expected-note{{cannot be used in a constant expression}}
+};
 
 template <typename X>
 int foo2() {
   X a = 0x61;
   fn1<char>(a);
+  (void)v1<int>;
+  (void)S::t<int>; // expected-note{{in instantiation of static data member 'S::t<int>' requested here}}
   return 0;
 }
 
Index: lib/Sema/SemaTemplateInstantiateDecl.cpp
===================================================================
--- lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -3932,6 +3932,7 @@
 
     {
       ContextRAII SwitchContext(*this, Var->getDeclContext());
+      VarTemplateSpecializationRAII V(*this, Var);
       Init = SubstInitializer(OldVar->getInit(), TemplateArgs,
                               OldVar->getInitStyle() == VarDecl::CallInit);
     }
Index: lib/Sema/SemaTemplateInstantiate.cpp
===================================================================
--- lib/Sema/SemaTemplateInstantiate.cpp
+++ lib/Sema/SemaTemplateInstantiate.cpp
@@ -33,34 +33,10 @@
 // Template Instantiation Support
 //===----------------------------------------------------------------------===/
 
-/// \brief Retrieve the template argument list(s) that should be used to
-/// instantiate the definition of the given declaration.
-///
-/// \param D the declaration for which we are computing template instantiation
-/// arguments.
-///
-/// \param Innermost if non-NULL, the innermost template argument list.
-///
-/// \param RelativeToPrimary true if we should get the template
-/// arguments relative to the primary template, even when we're
-/// dealing with a specialization. This is only relevant for function
-/// template specializations.
-///
-/// \param Pattern If non-NULL, indicates the pattern from which we will be
-/// instantiating the definition of the given declaration, \p D. This is
-/// used to determine the proper set of template instantiation arguments for
-/// friend function template specializations.
-MultiLevelTemplateArgumentList
-Sema::getTemplateInstantiationArgs(NamedDecl *D, 
-                                   const TemplateArgumentList *Innermost,
-                                   bool RelativeToPrimary,
-                                   const FunctionDecl *Pattern) {
-  // Accumulate the set of template argument lists in this structure.
-  MultiLevelTemplateArgumentList Result;
-
-  if (Innermost)
-    Result.addOuterTemplateArguments(Innermost);
-  
+static void
+getTemplateInstantiationArgs(Sema &S, NamedDecl *D, bool RelativeToPrimary,
+                             const FunctionDecl *Pattern,
+                             MultiLevelTemplateArgumentList &Result) {
   DeclContext *Ctx = dyn_cast<DeclContext>(D);
   if (!Ctx) {
     Ctx = D->getDeclContext();
@@ -71,7 +47,7 @@
       // We're done when we hit an explicit specialization.
       if (Spec->getSpecializationKind() == TSK_ExplicitSpecialization &&
           !isa<VarTemplatePartialSpecializationDecl>(Spec))
-        return Result;
+        return;
 
       Result.addOuterTemplateArguments(&Spec->getTemplateInstantiationArgs());
 
@@ -84,11 +60,11 @@
       if (VarTemplatePartialSpecializationDecl *Partial =
               Specialized.dyn_cast<VarTemplatePartialSpecializationDecl *>()) {
         if (Partial->isMemberSpecialization())
-          return Result;
+          return;
       } else {
         VarTemplateDecl *Tmpl = Specialized.get<VarTemplateDecl *>();
         if (Tmpl->isMemberSpecialization())
-          return Result;
+          return;
       }
     }
 
@@ -103,7 +79,7 @@
                                       = dyn_cast<TemplateTemplateParmDecl>(D)) {
         for (unsigned I = 0, N = TTP->getDepth() + 1; I != N; ++I)
           Result.addOuterTemplateArguments(None);
-        return Result;
+        return;
       }
     }
   }
@@ -165,11 +141,21 @@
         RelativeToPrimary = false;
         continue;
       }
+
+      // Break if this function is a lambda call operator used to initialize
+      // a variable template specialization. The template arguments of the
+      // variable template specialization will be added later in
+      // Sema::getTemplateInstantiationArgs.
+      if (isLambdaCallOperator(Function))
+        if (auto *VT = S.getVarTemplateSpecDecl())
+          if (VT->getDeclContext() ==
+              cast<CXXMethodDecl>(Function)->getParent()->getDeclContext())
+        break;
     } else if (CXXRecordDecl *Rec = dyn_cast<CXXRecordDecl>(Ctx)) {
       if (ClassTemplateDecl *ClassTemplate = Rec->getDescribedClassTemplate()) {
         QualType T = ClassTemplate->getInjectedClassNameSpecialization();
         const TemplateSpecializationType *TST =
-            cast<TemplateSpecializationType>(Context.getCanonicalType(T));
+            cast<TemplateSpecializationType>(S.Context.getCanonicalType(T));
         Result.addOuterTemplateArguments(
             llvm::makeArrayRef(TST->getArgs(), TST->getNumArgs()));
         if (ClassTemplate->isMemberSpecialization())
@@ -180,6 +166,43 @@
     Ctx = Ctx->getParent();
     RelativeToPrimary = false;
   }
+}
+
+/// \brief Retrieve the template argument list(s) that should be used to
+/// instantiate the definition of the given declaration.
+///
+/// \param D the declaration for which we are computing template instantiation
+/// arguments.
+///
+/// \param Innermost if non-NULL, the innermost template argument list.
+///
+/// \param RelativeToPrimary true if we should get the template
+/// arguments relative to the primary template, even when we're
+/// dealing with a specialization. This is only relevant for function
+/// template specializations.
+///
+/// \param Pattern If non-NULL, indicates the pattern from which we will be
+/// instantiating the definition of the given declaration, \p D. This is
+/// used to determine the proper set of template instantiation arguments for
+/// friend function template specializations.
+MultiLevelTemplateArgumentList
+Sema::getTemplateInstantiationArgs(NamedDecl *D,
+                                   const TemplateArgumentList *Innermost,
+                                   bool RelativeToPrimary,
+                                   const FunctionDecl *Pattern) {
+  // Accumulate the set of template argument lists in this structure.
+  MultiLevelTemplateArgumentList Result;
+
+  if (Innermost)
+    Result.addOuterTemplateArguments(Innermost);
+
+  ::getTemplateInstantiationArgs(*this, D, RelativeToPrimary, Pattern, Result);
+
+  // If we are instantiating the initializer of a variable template, add the
+  // template argument lists of the variable template specialization.
+  if ((D = getVarTemplateSpecDecl()))
+    ::getTemplateInstantiationArgs(*this, D, RelativeToPrimary, Pattern,
+                                   Result);
 
   return Result;
 }
@@ -1685,7 +1708,7 @@
       // Instantiate default arguments for methods of local classes (DR1484)
       // and non-defining declarations.
       Sema::ContextRAII SavedContext(*this, OwningFunc);
-      LocalInstantiationScope Local(*this);
+      LocalInstantiationScope Local(*this, true);
       ExprResult NewArg = SubstExpr(Arg, TemplateArgs);
       if (NewArg.isUsable()) {
         // It would be nice if we still had this.
Index: lib/Sema/SemaTemplate.cpp
===================================================================
--- lib/Sema/SemaTemplate.cpp
+++ lib/Sema/SemaTemplate.cpp
@@ -429,7 +429,12 @@
   bool MightBeCxx11UnevalField =
       getLangOpts().CPlusPlus11 && isUnevaluatedContext();
 
-  if (!MightBeCxx11UnevalField && !isAddressOfOperand &&
+  // Check if the nested name specifier is an enum type.
+  bool IsEnum = false;
+  if (NestedNameSpecifier *NNS = SS.getScopeRep())
+    IsEnum = dyn_cast_or_null<EnumType>(NNS->getAsType());
+
+  if (!MightBeCxx11UnevalField && !isAddressOfOperand && !IsEnum &&
       isa<CXXMethodDecl>(DC) && cast<CXXMethodDecl>(DC)->isInstance()) {
     QualType ThisType = cast<CXXMethodDecl>(DC)->getThisType(Context);
 
Index: lib/Sema/Sema.cpp
===================================================================
--- lib/Sema/Sema.cpp
+++ lib/Sema/Sema.cpp
@@ -74,7 +74,8 @@
            TranslationUnitKind TUKind,
            CodeCompleteConsumer *CodeCompleter)
   : ExternalSource(nullptr),
-    isMultiplexExternalSource(false), FPFeatures(pp.getLangOpts()),
+    isMultiplexExternalSource(false), VarTemplateSpec(nullptr),
+    FPFeatures(pp.getLangOpts()),
     LangOpts(pp.getLangOpts()), PP(pp), Context(ctxt), Consumer(consumer),
     Diags(PP.getDiagnostics()), SourceMgr(PP.getSourceManager()),
     CollectStats(false), CodeCompleter(CodeCompleter),
Index: include/clang/Sema/Sema.h
===================================================================
--- include/clang/Sema/Sema.h
+++ include/clang/Sema/Sema.h
@@ -288,6 +288,8 @@
   }
   bool shouldLinkPossiblyHiddenDecl(LookupResult &Old, const NamedDecl *New);
 
+  VarTemplateSpecializationDecl *VarTemplateSpec;
+
 public:
   typedef OpaquePtr<DeclGroupRef> DeclGroupPtrTy;
   typedef OpaquePtr<TemplateName> TemplateTy;
@@ -665,6 +667,17 @@
     }
   };
 
+  class VarTemplateSpecializationRAII {
+    Sema &S;
+  public:
+    VarTemplateSpecializationRAII(Sema &S, VarDecl *Var) : S(S) {
+      S.setVarTemplateSpecDecl(dyn_cast<VarTemplateSpecializationDecl>(Var));
+    }
+    ~VarTemplateSpecializationRAII() {
+      S.clearVarTemplateSpecDecl();
+    }
+  };
+
   /// \brief RAII object to handle the state changes required to synthesize
   /// a function body.
   class SynthesizedFunctionScope {
@@ -3689,6 +3702,18 @@
 
   void DiscardCleanupsInEvaluationContext();
 
+  void setVarTemplateSpecDecl(VarTemplateSpecializationDecl *V) {
+    VarTemplateSpec = V;
+  }
+
+  void clearVarTemplateSpecDecl() {
+    VarTemplateSpec = nullptr;
+  }
+
+  VarTemplateSpecializationDecl *getVarTemplateSpecDecl() {
+    return VarTemplateSpec;
+  }
+
   ExprResult TransformToPotentiallyEvaluated(Expr *E);
   ExprResult HandleExprEvaluationContextForTypeof(Expr *E);
 
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