[PATCH] D155705: [clang] Fix specialization of non-templated member classes of class templates

[Mariya Podchishchaeva via Phabricator via cfe-commits]

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Explicit specialization doesn't increase depth of template parameters,
so need to be careful when gathering template parameters for
instantiation.
For the case:

  template<typename T>
  struct X {
    struct impl;
  };
  
  template <>
  struct X<int>::impl {
      template<int ct>
      int f() { return ct; };
  };

instantiation of `f` used to crash because type template parameter
`int` of explicit specialization was taken into account, but non-type
template parameter `ct` had zero depth and index so wrong parameter
ended up inside of a wrong handler.

Fixes https://github.com/llvm/llvm-project/issues/61159


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D155705

Files:
  clang/docs/ReleaseNotes.rst
  clang/lib/Sema/SemaTemplateInstantiate.cpp
  clang/test/SemaTemplate/gh61159.cpp


Index: clang/test/SemaTemplate/gh61159.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaTemplate/gh61159.cpp
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++20 %s
+// expected-no-diagnostics
+
+
+namespace GH61159 {
+template<typename T>
+struct X {
+  struct impl;
+};
+
+
+template <>
+struct X<int>::impl {
+    template<int ct>
+    int f() { return ct; };
+};
+
+void foo() {
+    X<int>::impl{}.f<17>();
+}
+}
Index: clang/lib/Sema/SemaTemplateInstantiate.cpp
===================================================================
--- clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -258,6 +258,11 @@
                                        /*Final=*/false);
   }
 
+  if (const MemberSpecializationInfo *MSInfo =
+          Rec->getMemberSpecializationInfo())
+    if (MSInfo->getTemplateSpecializationKind() == TSK_ExplicitSpecialization)
+      return Response::Done();
+
   bool IsFriend = Rec->getFriendObjectKind() ||
                   (Rec->getDescribedClassTemplate() &&
                    Rec->getDescribedClassTemplate()->getFriendObjectKind());
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -652,6 +652,8 @@
   (`#63169 <https://github.com/llvm/llvm-project/issues/63169>_`)
 - Fix crash when casting an object to an array type.
   (`#63758 <https://github.com/llvm/llvm-project/issues/63758>_`)
+- Fix crash on nested templated class with template function call.
+  (`#61159 <https://github.com/llvm/llvm-project/issues/61159>_`)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


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