chore(core): fix modernize-use-constraints (#8236)

libtransmission/.clang-tidy

@@ -3,7 +3,6 @@ HeaderFilterRegex: .*/libtransmission/.*
 
 # TODO: Enable `portability-template-virtual-member-function` after https://github.com/llvm/llvm-project/issues/139031 is fixed
 # TODO: Enable `cppcoreguidelines-pro-bounds-pointer-arithmetic` after converting all pointers to std::span
-# TODO: Enable `modernize-use-constraints` after GCC >= 10, clang 10
 # TODO: Enable `modernize-use-integer-sign-comparison` (P0586R2) after GCC >= 10.1, clang >= 13
 # PRs welcome to fix & re-enable any of these explicitly-disabled checks
 #
@@ -45,7 +44,6 @@ Checks: >
   -misc-non-private-member-variables-in-classes,
   modernize-*,
   -modernize-loop-convert,
-  -modernize-use-constraints,
   -modernize-use-integer-sign-comparison,
   -modernize-use-ranges,
   -modernize-use-trailing-return-type,

libtransmission/utils.cc

@@ -809,8 +809,9 @@ std::string_view tr_get_mime_type_for_filename(std::string_view filename)
 
 // --- tr_num_parse()
 
-template<typename T, std::enable_if_t<std::is_integral_v<T>, bool>>
+template<typename T>
 [[nodiscard]] std::optional<T> tr_num_parse(std::string_view str, std::string_view* remainder, int base)
+    requires std::is_integral_v<T>
 {
     auto val = T{};
     auto const* const begin_ch = std::data(str);
@@ -839,8 +840,9 @@ template std::optional<unsigned int> tr_num_parse(std::string_view str, std::str
 template std::optional<unsigned short> tr_num_parse(std::string_view str, std::string_view* remainder, int base);
 template std::optional<unsigned char> tr_num_parse(std::string_view str, std::string_view* remainder, int base);
 
-template<typename T, std::enable_if_t<std::is_floating_point_v<T>, bool>>
+template<typename T>
 [[nodiscard]] std::optional<T> tr_num_parse(std::string_view str, std::string_view* remainder)
+    requires std::is_floating_point_v<T>
 {
     auto const* const begin_ch = std::data(str);
     auto const* const end_ch = begin_ch + std::size(str);

libtransmission/utils.h

@@ -207,11 +207,13 @@ constexpr bool tr_strv_sep(std::string_view* sv, std::string_view* token, Args&&
 
 // ---
 
-template<typename T, std::enable_if_t<std::is_integral_v<T>, bool> = true>
-[[nodiscard]] std::optional<T> tr_num_parse(std::string_view str, std::string_view* setme_remainder = nullptr, int base = 10);
+template<typename T>
+[[nodiscard]] std::optional<T> tr_num_parse(std::string_view str, std::string_view* setme_remainder = nullptr, int base = 10)
+    requires std::is_integral_v<T>;
 
-template<typename T, std::enable_if_t<std::is_floating_point_v<T>, bool> = true>
-[[nodiscard]] std::optional<T> tr_num_parse(std::string_view str, std::string_view* setme_remainder = nullptr);
+template<typename T>
+[[nodiscard]] std::optional<T> tr_num_parse(std::string_view str, std::string_view* setme_remainder = nullptr)
+    requires std::is_floating_point_v<T>;
 
 /**
  * @brief Given a string like "1-4" or "1-4,6,9,14-51", this returns a