[clang] [Clang] Fix handling of brace ellison when building deduction guides (PR #94889)

[Haojian Wu via cfe-commits]

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@@ -10918,22 +10944,24 @@ QualType Sema::DeduceTemplateSpecializationFromInitializer(
       if (!(RD->getDefinition() && RD->isAggregate()))
         return;
       QualType Ty = Context.getRecordType(RD);
-      SmallVector<QualType, 8> ElementTypes;
-
-      InitListChecker CheckInitList(*this, Entity, ListInit, Ty, ElementTypes);
-      if (!CheckInitList.HadError()) {
+      auto BuildAggregateDeductionGuide = [&](MutableArrayRef<QualType>
+                                                  ElementTypes,
+                                              bool BracedVersion = false) {
+        if (ElementTypes.empty())
+          return;
         // C++ [over.match.class.deduct]p1.8:
         //   if e_i is of array type and x_i is a braced-init-list, T_i is an
         //   rvalue reference to the declared type of e_i and
         // C++ [over.match.class.deduct]p1.9:
-        //   if e_i is of array type and x_i is a bstring-literal, T_i is an
+        //   if e_i is of array type and x_i is a string-literal, T_i is an
         //   lvalue reference to the const-qualified declared type of e_i and
         // C++ [over.match.class.deduct]p1.10:
         //   otherwise, T_i is the declared type of e_i
-        for (int I = 0, E = ListInit->getNumInits();
+        for (int I = 0, E = BracedVersion ? ElementTypes.size()
+                                          : ListInit->getNumInits();
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hokein wrote:

this loop becomes harder to reason about, the iterator `I` is used to access two containers `ListInit`, `ElementTypes`, can we add some assertions to make sure we don't have out-of-bound issues here?

https://github.com/llvm/llvm-project/pull/94889