[Clang] Fix canonicalization of pack indexing types (#123209)

A canonicalized pack indexing should refer to a canonicalized pattern

Fixes #123033

Author: cor3ntin

clang/docs/ReleaseNotes.rst

@@ -952,6 +952,8 @@ Bug Fixes to C++ Support
 - Fixed a crash when __PRETTY_FUNCTION__ or __FUNCSIG__ (clang-cl) appears in the trailing return type of the lambda (#GH121274)
 - Fixed a crash caused by the incorrect construction of template arguments for CTAD alias guides when type
   constraints are applied. (#GH122134)
+- Fixed canonicalization of pack indexing types - Clang did not always recognized identical pack indexing. (#GH123033)
+
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/AST/ASTContext.cpp

@@ -6248,16 +6248,18 @@ QualType ASTContext::getPackIndexingType(QualType Pattern, Expr *IndexExpr,
     Canonical = getCanonicalType(Expansions[Index]);
   } else {
     llvm::FoldingSetNodeID ID;
-    PackIndexingType::Profile(ID, *this, Pattern, IndexExpr, FullySubstituted);
+    PackIndexingType::Profile(ID, *this, Pattern.getCanonicalType(), IndexExpr,
+                              FullySubstituted);
     void *InsertPos = nullptr;
     PackIndexingType *Canon =
         DependentPackIndexingTypes.FindNodeOrInsertPos(ID, InsertPos);
     if (!Canon) {
       void *Mem = Allocate(
           PackIndexingType::totalSizeToAlloc<QualType>(Expansions.size()),
           TypeAlignment);
-      Canon = new (Mem) PackIndexingType(*this, QualType(), Pattern, IndexExpr,
-                                         FullySubstituted, Expansions);
+      Canon = new (Mem)
+          PackIndexingType(*this, QualType(), Pattern.getCanonicalType(),
+                           IndexExpr, FullySubstituted, Expansions);
       DependentPackIndexingTypes.InsertNode(Canon, InsertPos);
     }
     Canonical = QualType(Canon, 0);

clang/test/SemaCXX/cxx2c-pack-indexing.cpp

@@ -321,3 +321,26 @@ namespace GH121242 {
         (void)z<X{}>;
     }
 } // namespace GH121242
+
+namespace GH123033 {
+  template <class... Types>
+  requires __is_same_as(Types...[0], int)
+  void print(double d);
+
+  template <class... Types>
+  requires  __is_same_as(Types...[0], int)
+  void print(double d);
+
+  template <class... Types>
+  Types...[0] convert(double d);
+
+  template <class... Types>
+  Types...[0] convert(double d) {
+      return static_cast<Types...[0]>(d);
+  }
+
+  void f() {
+      print<int, int>(12.34);
+      convert<int, int>(12.34);
+  }
+}