diff --git a/include/pybind11/detail/descr.h b/include/pybind11/detail/descr.h
index e7a5e2c14..e4baa383b 100644
--- a/include/pybind11/detail/descr.h
+++ b/include/pybind11/detail/descr.h
@@ -20,21 +20,69 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 #    define PYBIND11_DESCR_CONSTEXPR const
 #endif
 
+// * MSVC 2017 does not support __builtin_FILE(), __builtin_LINE().
+// * Intel 2021.6.0.20220226 (g++ 9.4 mode) __builtin_LINE() is unreliable
+//   (line numbers vary between translation units).
+#if !defined(PYBIND11_DETAIL_DESCR_SRC_LOC_ON) && !defined(PYBIND11_DETAIL_DESCR_SRC_LOC_OFF)     \
+    && !defined(__INTEL_COMPILER)                                                                 \
+    && ((defined(_MSC_VER) && _MSC_VER >= 1920) || defined(PYBIND11_CPP17))
+#    define PYBIND11_DETAIL_DESCR_SRC_LOC_ON
+#endif
+
+#ifdef PYBIND11_DETAIL_DESCR_SRC_LOC_ON
+
+struct src_loc {
+    const char *file;
+    unsigned line;
+
+    constexpr src_loc(const char *file, unsigned line) : file(file), line(line) {}
+
+    static constexpr src_loc here(const char *file = __builtin_FILE(),
+                                  unsigned line = __builtin_LINE()) {
+        return src_loc(file, line);
+    }
+
+    constexpr src_loc if_known_or(const src_loc &other) const {
+        if (file != nullptr) {
+            return *this;
+        }
+        return other;
+    }
+};
+
+#else
+
+struct src_loc {
+    constexpr src_loc(const char *, unsigned) {}
+
+    static constexpr src_loc here(const char * = nullptr, unsigned = 0) {
+        return src_loc(nullptr, 0);
+    }
+
+    constexpr src_loc if_known_or(const src_loc &) const { return *this; }
+};
+
+#endif
+
 /* Concatenate type signatures at compile time */
 template <size_t N, typename... Ts>
 struct descr {
     char text[N + 1]{'\0'};
+    src_loc sloc;
 
-    constexpr descr() = default;
+    explicit constexpr descr(src_loc sloc) : sloc(sloc) {}
     // NOLINTNEXTLINE(google-explicit-constructor)
-    constexpr descr(char const (&s)[N + 1]) : descr(s, make_index_sequence<N>()) {}
+    constexpr descr(char const (&s)[N + 1], src_loc sloc = src_loc::here())
+        : descr(s, make_index_sequence<N>(), sloc) {}
 
     template <size_t... Is>
-    constexpr descr(char const (&s)[N + 1], index_sequence<Is...>) : text{s[Is]..., '\0'} {}
+    constexpr descr(char const (&s)[N + 1], index_sequence<Is...>, src_loc sloc = src_loc::here())
+        : text{s[Is]..., '\0'}, sloc(sloc) {}
 
     template <typename... Chars>
     // NOLINTNEXTLINE(google-explicit-constructor)
-    constexpr descr(char c, Chars... cs) : text{c, static_cast<char>(cs)..., '\0'} {}
+    constexpr descr(src_loc sloc, char c, Chars... cs)
+        : text{c, static_cast<char>(cs)..., '\0'}, sloc(sloc) {}
 
     static constexpr std::array<const std::type_info *, sizeof...(Ts) + 1> types() {
         return {{&typeid(Ts)..., nullptr}};
@@ -47,7 +95,8 @@ constexpr descr<N1 + N2, Ts1..., Ts2...> plus_impl(const descr<N1, Ts1...> &a,
                                                    index_sequence<Is1...>,
                                                    index_sequence<Is2...>) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(b);
-    return {a.text[Is1]..., b.text[Is2]...};
+    return descr<N1 + N2, Ts1..., Ts2...>{
+        a.sloc.if_known_or(b.sloc), a.text[Is1]..., b.text[Is2]...};
 }
 
 template <size_t N1, size_t N2, typename... Ts1, typename... Ts2>
@@ -57,27 +106,31 @@ constexpr descr<N1 + N2, Ts1..., Ts2...> operator+(const descr<N1, Ts1...> &a,
 }
 
 template <size_t N>
-constexpr descr<N - 1> const_name(char const (&text)[N]) {
-    return descr<N - 1>(text);
+constexpr descr<N - 1> const_name(char const (&text)[N], src_loc sloc = src_loc::here()) {
+    return descr<N - 1>(text, sloc);
+}
+constexpr descr<0> const_name(char const (&)[1], src_loc sloc = src_loc::here()) {
+    return descr<0>(sloc);
 }
-constexpr descr<0> const_name(char const (&)[1]) { return {}; }
 
 template <size_t Rem, size_t... Digits>
 struct int_to_str : int_to_str<Rem / 10, Rem % 10, Digits...> {};
 template <size_t... Digits>
 struct int_to_str<0, Digits...> {
     // WARNING: This only works with C++17 or higher.
-    static constexpr auto digits = descr<sizeof...(Digits)>(('0' + Digits)...);
+    static constexpr auto digits = descr<sizeof...(Digits)>(src_loc::here(), ('0' + Digits)...);
 };
 
 // Ternary description (like std::conditional)
 template <bool B, size_t N1, size_t N2>
-constexpr enable_if_t<B, descr<N1 - 1>> const_name(char const (&text1)[N1], char const (&)[N2]) {
-    return const_name(text1);
+constexpr enable_if_t<B, descr<N1 - 1>>
+const_name(char const (&text1)[N1], char const (&)[N2], src_loc sloc = src_loc::here()) {
+    return const_name(text1, sloc);
 }
 template <bool B, size_t N1, size_t N2>
-constexpr enable_if_t<!B, descr<N2 - 1>> const_name(char const (&)[N1], char const (&text2)[N2]) {
-    return const_name(text2);
+constexpr enable_if_t<!B, descr<N2 - 1>>
+const_name(char const (&)[N1], char const (&text2)[N2], src_loc sloc = src_loc::here()) {
+    return const_name(text2, sloc);
 }
 
 template <bool B, typename T1, typename T2>
@@ -91,12 +144,13 @@ constexpr enable_if_t<!B, T2> const_name(const T1 &, const T2 &d) {
 
 template <size_t Size>
 auto constexpr const_name() -> remove_cv_t<decltype(int_to_str<Size / 10, Size % 10>::digits)> {
+    // src_loc not tracked (irrelevant in this situation, at least at the moment).
     return int_to_str<Size / 10, Size % 10>::digits;
 }
 
 template <typename Type>
-constexpr descr<1, Type> const_name() {
-    return {'%'};
+constexpr descr<1, Type> const_name(src_loc sloc = src_loc::here()) {
+    return {sloc, '%'};
 }
 
 // If "_" is defined as a macro, py::detail::_ cannot be provided.
@@ -106,16 +160,18 @@ constexpr descr<1, Type> const_name() {
 #ifndef _
 #    define PYBIND11_DETAIL_UNDERSCORE_BACKWARD_COMPATIBILITY
 template <size_t N>
-constexpr descr<N - 1> _(char const (&text)[N]) {
-    return const_name<N>(text);
+constexpr descr<N - 1> _(char const (&text)[N], src_loc sloc = src_loc::here()) {
+    return const_name<N>(text, sloc);
 }
 template <bool B, size_t N1, size_t N2>
-constexpr enable_if_t<B, descr<N1 - 1>> _(char const (&text1)[N1], char const (&text2)[N2]) {
-    return const_name<B, N1, N2>(text1, text2);
+constexpr enable_if_t<B, descr<N1 - 1>>
+_(char const (&text1)[N1], char const (&text2)[N2], src_loc sloc = src_loc::here()) {
+    return const_name<B, N1, N2>(text1, text2, sloc);
 }
 template <bool B, size_t N1, size_t N2>
-constexpr enable_if_t<!B, descr<N2 - 1>> _(char const (&text1)[N1], char const (&text2)[N2]) {
-    return const_name<B, N1, N2>(text1, text2);
+constexpr enable_if_t<!B, descr<N2 - 1>>
+_(char const (&text1)[N1], char const (&text2)[N2], src_loc sloc = src_loc::here()) {
+    return const_name<B, N1, N2>(text1, text2, sloc);
 }
 template <bool B, typename T1, typename T2>
 constexpr enable_if_t<B, T1> _(const T1 &d1, const T2 &d2) {
@@ -128,15 +184,16 @@ constexpr enable_if_t<!B, T2> _(const T1 &d1, const T2 &d2) {
 
 template <size_t Size>
 auto constexpr _() -> remove_cv_t<decltype(int_to_str<Size / 10, Size % 10>::digits)> {
+    // src_loc not tracked (irrelevant in this situation, at least at the moment).
     return const_name<Size>();
 }
 template <typename Type>
-constexpr descr<1, Type> _() {
-    return const_name<Type>();
+constexpr descr<1, Type> _(src_loc sloc = src_loc::here()) {
+    return const_name<Type>(sloc);
 }
 #endif // #ifndef _
 
-constexpr descr<0> concat() { return {}; }
+constexpr descr<0> concat(src_loc sloc = src_loc::here()) { return descr<0>{sloc}; }
 
 template <size_t N, typename... Ts>
 constexpr descr<N, Ts...> concat(const descr<N, Ts...> &descr) {
@@ -151,7 +208,8 @@ constexpr auto concat(const descr<N, Ts...> &d, const Args &...args)
 
 template <size_t N, typename... Ts>
 constexpr descr<N + 2, Ts...> type_descr(const descr<N, Ts...> &descr) {
-    return const_name("{") + descr + const_name("}");
+    // Ensure that src_loc of existing descr is used.
+    return const_name("{", src_loc{nullptr, 0}) + descr + const_name("}");
 }
 
 PYBIND11_NAMESPACE_END(detail)
diff --git a/include/pybind11/detail/type_caster_odr_guard.h b/include/pybind11/detail/type_caster_odr_guard.h
index 97092e0ab..4ae6d91fe 100644
--- a/include/pybind11/detail/type_caster_odr_guard.h
+++ b/include/pybind11/detail/type_caster_odr_guard.h
@@ -4,18 +4,16 @@
 
 #pragma once
 
+#include "descr.h"
+
 // The type_caster ODR guard feature requires Translation-Unit-local entities
 // (https://en.cppreference.com/w/cpp/language/tu_local), a C++20 feature, but
 // almost all tested C++17 compilers support this feature already.
+// This highly correlates with the preconditions for PYBIND11_DETAIL_DESCR_SRC_LOC_ON.
 #if !defined(PYBIND11_TYPE_CASTER_ODR_GUARD_ON) && !defined(PYBIND11_TYPE_CASTER_ODR_GUARD_OFF)   \
-    && !defined(__INTEL_COMPILER)                                                                 \
-    && ((defined(_MSC_VER) && _MSC_VER >= 1920) || defined(PYBIND11_CPP17))
+    && defined(PYBIND11_DETAIL_DESCR_SRC_LOC_ON)
 #    define PYBIND11_TYPE_CASTER_ODR_GUARD_ON
 #endif
-// To explain the above:
-// * MSVC 2017 does not support __builtin_FILE(), __builtin_LINE().
-// * Intel 2021.6.0.20220226 (g++ 9.4 mode) __builtin_LINE() is unreliable
-//   (line numbers vary between translation units).
 
 #ifndef PYBIND11_TYPE_CASTER_ODR_GUARD_ON
 
@@ -31,7 +29,6 @@
 
 #    include "../pytypes.h"
 #    include "common.h"
-#    include "descr.h"
 #    include "typeid.h"
 
 #    include <cstdio>
@@ -46,19 +43,6 @@
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-struct src_loc {
-    const char *file;
-    unsigned line;
-
-    // constexpr src_loc() : file(nullptr), line(0) {}
-    constexpr src_loc(const char *file, unsigned line) : file(file), line(line) {}
-
-    static constexpr src_loc here(const char *file = __builtin_FILE(),
-                                  unsigned line = __builtin_LINE()) {
-        return src_loc(file, line);
-    }
-};
-
 inline std::unordered_map<std::type_index, std::string> &type_caster_odr_guard_registry() {
     static std::unordered_map<std::type_index, std::string> reg;
     return reg;