[PATCH] D156064: [SemaCXX] Recognise initializer_list injected-class-name types as initializer_lists

[Mital Ashok via Phabricator via cfe-commits]

MitalAshok updated this revision to Diff 544046.
MitalAshok added a comment.

Rebase changelog to clang 18, add more tests


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D156064/new/

https://reviews.llvm.org/D156064

Files:
  clang/docs/ReleaseNotes.rst
  clang/lib/Sema/SemaDeclCXX.cpp
  clang/lib/Sema/SemaInit.cpp
  clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp


Index: clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
===================================================================
--- clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
+++ clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
@@ -12,14 +12,19 @@
     size_t n;
     initializer_list();
   };
-  // FIXME: This should probably not be necessary.
-  template<typename T> initializer_list(initializer_list<T>) -> initializer_list<T>;
 }
 
 template<typename T> constexpr bool has_type(...) { return false; }
 template<typename T> constexpr bool has_type(T&) { return true; }
 
-std::initializer_list il = {1, 2, 3, 4, 5};
+std::initializer_list il1 = {1, 2, 3, 4, 5};
+auto il2 = std::initializer_list{1, 2, 3, 4};
+auto il3 = std::initializer_list{il1};
+auto il4 = std::initializer_list{il1, il1, il1};
+static_assert(has_type<std::initializer_list<int>>(il1));
+static_assert(has_type<std::initializer_list<int>>(il2));
+static_assert(has_type<std::initializer_list<int>>(il3));
+static_assert(has_type<std::initializer_list<std::initializer_list<int>>>(il4));
 
 template<typename T> struct vector {
   template<typename Iter> vector(Iter, Iter);
Index: clang/lib/Sema/SemaInit.cpp
===================================================================
--- clang/lib/Sema/SemaInit.cpp
+++ clang/lib/Sema/SemaInit.cpp
@@ -10589,8 +10589,6 @@
   // FIXME: Perform "exact type" matching first, per CWG discussion?
   //        Or implement this via an implied 'T(T) -> T' deduction guide?
 
-  // FIXME: Do we need/want a std::initializer_list<T> special case?
-
   // Look up deduction guides, including those synthesized from constructors.
   //
   // C++1z [over.match.class.deduct]p1:
Index: clang/lib/Sema/SemaDeclCXX.cpp
===================================================================
--- clang/lib/Sema/SemaDeclCXX.cpp
+++ clang/lib/Sema/SemaDeclCXX.cpp
@@ -11749,11 +11749,17 @@
 
     Template = Specialization->getSpecializedTemplate();
     Arguments = Specialization->getTemplateArgs().data();
-  } else if (const TemplateSpecializationType *TST =
-                 Ty->getAs<TemplateSpecializationType>()) {
-    Template = dyn_cast_or_null<ClassTemplateDecl>(
-        TST->getTemplateName().getAsTemplateDecl());
-    Arguments = TST->template_arguments().begin();
+  } else {
+    const TemplateSpecializationType *TST = nullptr;
+    if (auto *ICN = Ty->getAs<InjectedClassNameType>())
+      TST = ICN->getInjectedTST();
+    else
+      TST = Ty->getAs<TemplateSpecializationType>();
+    if (TST) {
+      Template = dyn_cast_or_null<ClassTemplateDecl>(
+          TST->getTemplateName().getAsTemplateDecl());
+      Arguments = TST->template_arguments().begin();
+    }
   }
   if (!Template)
     return false;
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -107,6 +107,9 @@
 
 Bug Fixes to C++ Support
 ^^^^^^^^^^^^^^^^^^^^^^^^
+- Fix CTAD for ``std::initializer_list``. This allows
+  ``std::initializer_list{1, 2, 3}`` to be a ``std::initializer_list<int>``
+  as intended.
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^


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