[clang] Fix missing initializer for inline static template member with auto caused by delayed template instantiation.

[Clang] Fix missing initializer for inline static template member with auto caused by delayed template instantiation.

Author: dty2

clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -6027,8 +6027,12 @@ void Sema::BuildVariableInstantiation(
   Context.setManglingNumber(NewVar, Context.getManglingNumber(OldVar));
   Context.setStaticLocalNumber(NewVar, Context.getStaticLocalNumber(OldVar));
 
+  bool VarTemplateWithAutoType =
+      OldVar->getTypeSourceInfo()->getType()->getAs<AutoType>();
+
   // Figure out whether to eagerly instantiate the initializer.
-  if (InstantiatingVarTemplate || InstantiatingVarTemplatePartialSpec) {
+  if (!VarTemplateWithAutoType &&
+      (InstantiatingVarTemplate || InstantiatingVarTemplatePartialSpec)) {
     // We're producing a template. Don't instantiate the initializer yet.
   } else if (NewVar->getType()->isUndeducedType()) {
     // We need the type to complete the declaration of the variable.

clang/test/SemaTemplate/cxx17-inline-variables.cpp

@@ -27,3 +27,15 @@ template <typename T> constexpr int A<T>::n = sizeof(A) + sizeof(T);
 template <typename T> inline constexpr int A<T>::m = sizeof(A) + sizeof(T);
 static_assert(A<int>().f() == 5);
 static_assert(A<int>().g() == 5);
+
+template <typename T> struct InlineAuto {
+  template <typename G> inline static auto var = 5;
+};
+
+template <typename> struct PartialInlineAuto {
+  template <typename, typename> inline static auto var = 6;
+  template <typename T> inline static auto var<int, T> = 7;
+};
+
+int inlineauot = InlineAuto<int>::var<int>;
+int partialinlineauot = PartialInlineAuto<int>::var<int, int>;