diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -161,10 +161,9 @@
         if (isGenericLambdaCallOperatorOrStaticInvokerSpecialization(Function))
           break;
 
-      } else if (FunctionTemplateDecl *FunTmpl
-                                   = Function->getDescribedFunctionTemplate()) {
-        // Add the "injected" template arguments.
-        Result.addOuterTemplateArguments(FunTmpl->getInjectedTemplateArgs());
+      } else if (Function->getDescribedFunctionTemplate()) {
+        assert(Result.getNumSubstitutedLevels() == 0 &&
+               "Outer template not instantiated?");
       }
 
       // If this is a friend declaration and it declares an entity at
@@ -180,11 +179,8 @@
       }
     } else if (CXXRecordDecl *Rec = dyn_cast<CXXRecordDecl>(Ctx)) {
       if (ClassTemplateDecl *ClassTemplate = Rec->getDescribedClassTemplate()) {
-        QualType T = ClassTemplate->getInjectedClassNameSpecialization();
-        const TemplateSpecializationType *TST =
-            cast<TemplateSpecializationType>(Context.getCanonicalType(T));
-        Result.addOuterTemplateArguments(
-            llvm::makeArrayRef(TST->getArgs(), TST->getNumArgs()));
+        assert(Result.getNumSubstitutedLevels() == 0 &&
+               "Outer template not instantiated?");
         if (ClassTemplate->isMemberSpecialization())
           break;
       }
diff --git a/clang/test/SemaTemplate/generic-lambda.cpp b/clang/test/SemaTemplate/generic-lambda.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/SemaTemplate/generic-lambda.cpp
@@ -0,0 +1,62 @@
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify %s
+
+// expected-no-diagnostics
+
+template <class T, class U> constexpr bool is_same_v = false;
+template <class T> constexpr bool is_same_v<T, T> = true;
+template <class T, class U>
+concept is_same = is_same_v<T, U>;
+
+template <class T> struct X {};
+template <class T, class U>
+concept C1 = is_same<T, X<U>>;
+
+template <class T1> X<X<X<T1>>> t1() {
+  return []<class T2>(T2) -> X<X<T2>> {
+    struct S {
+      static X<X<T2>> f() {
+        return []<class T3>(T3) -> X<T3> {
+          static_assert(is_same<T2, X<T1>>);
+          static_assert(is_same<T3, X<T2>>);
+          return X<T3>();
+        }(X<T2>());
+      }
+    };
+    return S::f();
+  }(X<T1>());
+};
+template X<X<X<int>>> t1<int>();
+
+#if 0 // FIXME: crashes
+template<class T1> auto t2() {
+  return []<class T2>(T2) {
+    struct S {
+      static auto f() {
+        return []<class T3>(T3) {
+          static_assert(is_same<T2, X<T1>>);
+          static_assert(is_same<T3, X<T2>>);
+          return X<T3>();
+        }(X<T2>());
+      }
+    };
+    return S::f();
+  }(X<T1>());
+};
+template auto t2<int>();
+static_assert(is_same<decltype(t2<int>()), X<X<X<int>>>>);
+
+template<class T1> C1<X<X<T1>>> auto t3() {
+  return []<C1<T1> T2>(T2) -> C1<X<T2>> auto {
+    struct S {
+      static auto f() {
+        return []<C1<T2> T3>(T3) -> C1<T3> auto {
+          return X<T3>();
+        }(X<T2>());
+      }
+    };
+    return S::f();
+  }(X<T1>());
+};
+template C1<X<X<int>>> auto t3<int>();
+static_assert(is_same<decltype(t3<int>()), X<X<X<int>>>>);
+#endif