diff --git a/clang/include/clang/AST/DeclCXX.h b/clang/include/clang/AST/DeclCXX.h
--- a/clang/include/clang/AST/DeclCXX.h
+++ b/clang/include/clang/AST/DeclCXX.h
@@ -1994,10 +1994,6 @@
     return getDeductionCandidateKind() == DeductionCandidateKind::Copy;
   }
 
-  bool isAggregateDeductionCandidate() const {
-    return getDeductionCandidateKind() == DeductionCandidateKind::Aggregate;
-  }
-
   // Implement isa/cast/dyncast/etc.
   static bool classof(const Decl *D) { return classofKind(D->getKind()); }
   static bool classofKind(Kind K) { return K == CXXDeductionGuide; }
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -10,7 +10,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "clang/AST/APValue.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/Expr.h"
@@ -10650,7 +10649,7 @@
       return;
 
     if (!AllowAggregateDeductionCandidate &&
-        GD->isAggregateDeductionCandidate())
+        GD->getDeductionCandidateKind() == DeductionCandidateKind::Aggregate)
       return;
 
     // C++ [over.match.list]p1.2: (second phase list initialization)
@@ -10674,10 +10673,10 @@
           TmpInits.push_back(DI->getInit());
         else
           TmpInits.push_back(E);
-      AddTemplateOverloadCandidate(TD, FoundDecl, /*ExplicitArgs*/ nullptr,
+      AddTemplateOverloadCandidate(TD, FoundDecl, /*ExplicitArgs=*/nullptr,
                                    TmpInits, Candidates,
                                    SuppressUserConversions,
-                                   /*PartialOverloading*/ false, AllowExplicit,
+                                   /*PartialOverloading=*/false, AllowExplicit,
                                    ADLCallKind::NotADL, {}, true);
     } else {
       AddOverloadCandidate(GD, FoundDecl, Inits, Candidates,
@@ -10726,18 +10725,21 @@
                                       ElementTypes);
         if (!CheckInitList.HadError()) {
           // C++ [over.match.class.deduct]p1.8:
-          //   if e_i is of array type and x_i is a braced-init-list or
-          //   string-literal, T_i is an rvalue reference to the declared type
-          //   of e_i
+          //   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
+          //   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();
                i < e && !isa<PackExpansionType>(ElementTypes[i]); ++i)
             if (ElementTypes[i]->isArrayType()) {
               if (isa<InitListExpr>(ListInit->getInit(i)))
                 ElementTypes[i] =
                     Context.getRValueReferenceType(ElementTypes[i]);
-              else if (isa<StringLiteral>(ListInit->getInit(i)))
-                // This deviates from the wording which is incorrect.
-                // See https://github.com/cplusplus/draft/issues/3898.
+              else if (isa<StringLiteral>(
+                           ListInit->getInit(i)->IgnoreParenImpCasts()))
                 ElementTypes[i] =
                     Context.getLValueReferenceType(ElementTypes[i]);
             }
@@ -10761,7 +10763,7 @@
           } else {
             CXXDeductionGuideDecl *GD = AggregateDeductionCandidates[Hash];
             FunctionTemplateDecl *TD = GD->getDescribedFunctionTemplate();
-            assert(TD);
+            assert(TD && "aggregate deduction candidate is function template");
             addDeductionCandidate(TD, GD, DeclAccessPair::make(TD, AS_public),
                                   OnlyListConstructors, true);
           }
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -7383,7 +7383,7 @@
   AddOverloadCandidate(
       Specialization, FoundDecl, Args, CandidateSet, SuppressUserConversions,
       PartialOverloading, AllowExplicit,
-      /*AllowExplicitConversions*/ false, IsADLCandidate, Conversions, PO,
+      /*AllowExplicitConversions=*/false, IsADLCandidate, Conversions, PO,
       Info.AggregateDeductionCandidateHasMismatchedArity);
 }
 
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -2590,11 +2590,11 @@
 
   // In case we were expanding a pack when we attempted to declare deduction
   // guides, turn off pack expansion for everything we're about to do.
-  ArgumentPackSubstitutionIndexRAII SubstIndex(*this, -1);
+  ArgumentPackSubstitutionIndexRAII SubstIndex(*this,
+                                               /*NewSubstitutionIndex=*/-1);
   // Create a template instantiation record to track the "instantiation" of
   // constructors into deduction guides.
-  // FIXME: Add a kind for this to give more meaningful diagnostics. But can
-  // this substitution process actually fail?
+  // FIXME: Add a kind for this to give more meaningful diagnostics.
   InstantiatingTemplate BuildingDeductionGuides(*this, Loc, Template);
   if (BuildingDeductionGuides.isInvalid())
     return nullptr;
@@ -2632,8 +2632,7 @@
   ArgumentPackSubstitutionIndexRAII SubstIndex(*this, -1);
   // Create a template instantiation record to track the "instantiation" of
   // constructors into deduction guides.
-  // FIXME: Add a kind for this to give more meaningful diagnostics. But can
-  // this substitution process actually fail?
+  // FIXME: Add a kind for this to give more meaningful diagnostics.
   InstantiatingTemplate BuildingDeductionGuides(*this, Loc, Template);
   if (BuildingDeductionGuides.isInvalid())
     return;
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -358,15 +358,14 @@
     for (TemplateArgument::pack_iterator
              XA = X.pack_begin(),
              XAEnd = X.pack_end(), YA = Y.pack_begin(), YAEnd = Y.pack_end();
-         XA != XAEnd; ++XA) {
+         XA != XAEnd; ++XA, ++YA) {
       if (YA != YAEnd) {
-      TemplateArgument Merged = checkDeducedTemplateArguments(
-          Context, DeducedTemplateArgument(*XA, X.wasDeducedFromArrayBound()),
-          DeducedTemplateArgument(*YA, Y.wasDeducedFromArrayBound()));
-      if (Merged.isNull() && !(XA->isNull() && YA->isNull()))
-        return DeducedTemplateArgument();
-      NewPack.push_back(Merged);
-        ++YA;
+        TemplateArgument Merged = checkDeducedTemplateArguments(
+            Context, DeducedTemplateArgument(*XA, X.wasDeducedFromArrayBound()),
+            DeducedTemplateArgument(*YA, Y.wasDeducedFromArrayBound()));
+        if (Merged.isNull() && !(XA->isNull() && YA->isNull()))
+          return DeducedTemplateArgument();
+        NewPack.push_back(Merged);
       } else {
         NewPack.push_back(*XA);
       }
@@ -993,7 +992,7 @@
   TemplateDeductionInfo &Info;
   unsigned PackElements = 0;
   bool IsPartiallyExpanded = false;
-  bool DeducePackIfNotAlreadyDeduced;
+  bool DeducePackIfNotAlreadyDeduced = false;
   /// The number of expansions, if we have a fully-expanded pack in this scope.
   std::optional<unsigned> FixedNumExpansions;