Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -492,6 +492,8 @@
 def err_decomp_decl_type : Error<
   "decomposition declaration cannot be declared with type %0; "
   "declared type must be 'auto' or reference to 'auto'">;
+def err_decomp_decl_constraint : Error<"decomposition declaration cannot be "
+                                       "declared with constrained 'auto'">;
 def err_decomp_decl_parens : Error<
   "decomposition declaration cannot be declared with parentheses">;
 def err_decomp_decl_template : Error<
Index: clang/lib/Sema/SemaDeclCXX.cpp
===================================================================
--- clang/lib/Sema/SemaDeclCXX.cpp
+++ clang/lib/Sema/SemaDeclCXX.cpp
@@ -760,11 +760,13 @@
   // C++17 [dcl.dcl]/8:
   //   The decl-specifier-seq shall contain only the type-specifier auto
   //   and cv-qualifiers.
-  // C++2a [dcl.dcl]/8:
-  //   If decl-specifier-seq contains any decl-specifier other than static,
-  //   thread_local, auto, or cv-qualifiers, the program is ill-formed.
+  // C++2a [dcl.pre]/6:
+  //   Each decl-specifier in the decl-specifier-seq shall be static,
+  //   thread_local, auto (9.2.9.6 [dcl.spec.auto]), or a cv-qualifier.
   auto &DS = D.getDeclSpec();
   {
+    // Note: While constrained-auto needs to be checked, we do so separately so
+    // we can emit a better diagnostic.
     SmallVector<StringRef, 8> BadSpecifiers;
     SmallVector<SourceLocation, 8> BadSpecifierLocs;
     SmallVector<StringRef, 8> CPlusPlus20Specifiers;
@@ -791,6 +793,7 @@
       BadSpecifiers.push_back("inline");
       BadSpecifierLocs.push_back(DS.getInlineSpecLoc());
     }
+
     if (!BadSpecifiers.empty()) {
       auto &&Err = Diag(BadSpecifierLocs.front(), diag::err_decomp_decl_spec);
       Err << (int)BadSpecifiers.size()
@@ -851,6 +854,20 @@
       D.setInvalidType();
   }
 
+  // Constrained auto is prohibited by [decl.pre]p6, so check that here.
+  if (DS.isConstrainedAuto()) {
+    TemplateIdAnnotation *TemplRep = DS.getRepAsTemplateId();
+    assert(TemplRep->Kind == TNK_Concept_template &&
+           "No other template kind should be possible for a constrained auto");
+
+    SourceRange TemplRange{TemplRep->TemplateNameLoc,
+                           TemplRep->RAngleLoc.isValid()
+                               ? TemplRep->RAngleLoc
+                               : TemplRep->TemplateNameLoc};
+    Diag(TemplRep->TemplateNameLoc, diag::err_decomp_decl_constraint)
+        << TemplRange << FixItHint::CreateRemoval(TemplRange);
+  }
+
   // Build the BindingDecls.
   SmallVector<BindingDecl*, 8> Bindings;
 
Index: clang/test/CXX/drs/dr26xx.cpp
===================================================================
--- clang/test/CXX/drs/dr26xx.cpp
+++ clang/test/CXX/drs/dr26xx.cpp
@@ -28,3 +28,32 @@
 }
 
 }
+
+namespace dr2635 { // dr2635: yes
+template<typename T>
+concept UnaryC = true;
+template<typename T, typename U>
+concept BinaryC = true;
+
+struct S{ int i, j; };
+S get_S();
+
+template<typename T>
+T get_T();
+
+void use() {
+  // expected-error@+1{{decomposition declaration cannot be declared with constrained 'auto'}}
+  UnaryC auto [a, b] = get_S();
+  // expected-error@+1{{decomposition declaration cannot be declared with constrained 'auto'}}
+  BinaryC<int> auto [c, d] = get_S();
+}
+
+template<typename T>
+void TemplUse() {
+  // expected-error@+1{{decomposition declaration cannot be declared with constrained 'auto'}}
+  UnaryC auto [a, b] = get_T<T>();
+  // expected-error@+1{{decomposition declaration cannot be declared with constrained 'auto'}}
+  BinaryC<T> auto [c, d] = get_T<T>();
+}
+
+}
Index: clang/www/cxx_dr_status.html
===================================================================
--- clang/www/cxx_dr_status.html
+++ clang/www/cxx_dr_status.html
@@ -15618,7 +15618,7 @@
     <td><a href="https://wg21.link/cwg2635">2635</a></td>
     <td>DR</td>
     <td>Constrained structured bindings</td>
-    <td class="none" align="center">Unknown</td>
+    <td class="unreleased" align="center">Clang 16</td>
   </tr>
   <tr id="2636">
     <td><a href="https://wg21.link/cwg2636">2636</a></td>