diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -741,23 +741,15 @@
 Optional<NormalizedConstraint>
 NormalizedConstraint::fromConstraintExprs(Sema &S, NamedDecl *D,
                                           ArrayRef<const Expr *> E) {
-  assert(E.size() != 0);
-  auto First = fromConstraintExpr(S, D, E[0]);
-  if (E.size() == 1)
-    return First;
-  auto Second = fromConstraintExpr(S, D, E[1]);
-  if (!Second)
+  auto Conjunction = fromConstraintExpr(S, D, E[0]);
+  if (!Conjunction)
     return None;
-  llvm::Optional<NormalizedConstraint> Conjunction;
-  Conjunction.emplace(S.Context, std::move(*First), std::move(*Second),
-                      CCK_Conjunction);
-  for (unsigned I = 2; I < E.size(); ++I) {
+  for (unsigned I = 1; I < E.size(); ++I) {
     auto Next = fromConstraintExpr(S, D, E[I]);
     if (!Next)
-      return llvm::Optional<NormalizedConstraint>{};
-    NormalizedConstraint NewConjunction(S.Context, std::move(*Conjunction),
-                                        std::move(*Next), CCK_Conjunction);
-    *Conjunction = std::move(NewConjunction);
+      return None;
+    Conjunction.emplace(S.Context, std::move(*Conjunction), std::move(*Next),
+                        CCK_Conjunction);
   }
   return Conjunction;
 }
diff --git a/clang/test/CXX/temp/temp.constr/temp.constr.normal/p1.cpp b/clang/test/CXX/temp/temp.constr/temp.constr.normal/p1.cpp
--- a/clang/test/CXX/temp/temp.constr/temp.constr.normal/p1.cpp
+++ b/clang/test/CXX/temp/temp.constr/temp.constr.normal/p1.cpp
@@ -67,3 +67,14 @@
 
   static_assert((foo<1>(), true));
 }
+
+namespace PR47174 {
+  // This checks that we don't crash with a failed substitution on the first constrained argument when
+  // performing normalization.
+  template<Bar2 T, True U> requires true struct S3;       // expected-note {{template is declared here}}
+  template<True T, True U> requires true struct S3<T, U>; // expected-error {{class template partial specialization is not more specialized than the primary template}}
+
+  // Same as above, for the second position (but this was already working).
+  template<True T, Bar2 U> requires true struct S4;       // expected-note {{template is declared here}}
+  template<True T, True U> requires true struct S4<T, U>; // expected-error {{class template partial specialization is not more specialized than the primary template}}
+} // namespace PR47174