[clang] 1510595 - [Sema] Mark explicit specialization declaration in a friend invalid

[Yuanfang Chen via cfe-commits]

Author: Yuanfang Chen
Date: 2021-12-15T10:26:55-08:00
New Revision: 1510595dce9c48b9e7ddd49becd422c4e5e66fc9

URL: https://github.com/llvm/llvm-project/commit/1510595dce9c48b9e7ddd49becd422c4e5e66fc9
DIFF: https://github.com/llvm/llvm-project/commit/1510595dce9c48b9e7ddd49becd422c4e5e66fc9.diff

LOG: [Sema] Mark explicit specialization declaration in a friend invalid

Down the path, if there is a implicit instantiation, this may trigger
the assertion "Member specialization must be an explicit specialization"
in `clang::FunctionDecl::setFunctionTemplateSpecialization`.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D113245

Added: 
    clang/test/CXX/temp/temp.spec/temp.expl.spec/p20-2.cpp

Modified: 
    clang/lib/Sema/SemaDecl.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index b1312a7ccc512..5e9c92db81b4a 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -9202,6 +9202,7 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
             << Name << RemoveRange
             << FixItHint::CreateRemoval(RemoveRange)
             << FixItHint::CreateInsertion(InsertLoc, "<>");
+          Invalid = true;
         }
       }
     } else {

diff  --git a/clang/test/CXX/temp/temp.spec/temp.expl.spec/p20-2.cpp b/clang/test/CXX/temp/temp.spec/temp.expl.spec/p20-2.cpp
new file mode 100644
index 0000000000000..7bc5f13cd7375
--- /dev/null
+++ b/clang/test/CXX/temp/temp.spec/temp.expl.spec/p20-2.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+template<typename T>
+void f(T);
+
+template<typename T>
+struct A {
+  // expected-error at +1{{cannot declare an explicit specialization in a friend}}
+  template <> friend void f<>(int) {}
+};
+
+// Makes sure implicit instantiation here does not trigger
+// the assertion "Member specialization must be an explicit specialization"
+void foo(void) {
+    A<int> a;
+}