Simplify function signature annotation and parsing

`type_descr` is now applied only to the final signature so that it only
marks the argument types, but not nested types (e.g. for tuples) or
return types.

include/pybind11/cast.h

@@ -778,7 +778,7 @@ template <typename T1, typename T2> struct is_copy_constructible<std::pair<T1, T
 template <typename type> class type_caster_base : public type_caster_generic {
     using itype = intrinsic_t<type>;
 public:
-    static constexpr auto name = type_descr(_<type>());
+    static constexpr auto name = _<type>();
 
     type_caster_base() : type_caster_base(typeid(type)) { }
     explicit type_caster_base(const std::type_info &info) : type_caster_generic(info) { }
@@ -900,7 +900,7 @@ public:
     protected: \
         type value; \
     public: \
-        static constexpr auto name = type_descr(py_name); \
+        static constexpr auto name = py_name; \
         template <typename T_, enable_if_t<std::is_same<type, remove_cv_t<T_>>::value, int> = 0> \
         static handle cast(T_ *src, return_value_policy policy, handle parent) { \
             if (!src) return none().release(); \
@@ -1049,7 +1049,7 @@ public:
 
     template <typename T> using cast_op_type = void*&;
     operator void *&() { return value; }
-    static constexpr auto name = type_descr(_("capsule"));
+    static constexpr auto name = _("capsule");
 private:
     void *value = nullptr;
 };
@@ -1289,7 +1289,7 @@ public:
         return value[0];
     }
 
-    static constexpr auto name = type_descr(_(PYBIND11_STRING_NAME));
+    static constexpr auto name = _(PYBIND11_STRING_NAME);
     template <typename _T> using cast_op_type = remove_reference_t<pybind11::detail::cast_op_type<_T>>;
 };
 
@@ -1314,9 +1314,7 @@ public:
         return cast_impl(std::forward<T>(src), policy, parent, indices{});
     }
 
-    static constexpr auto name = type_descr(
-        _("Tuple[") + detail::concat(make_caster<Ts>::name...) + _("]")
-    );
+    static constexpr auto name = _("Tuple[") + concat(make_caster<Ts>::name...) + _("]");
 
     template <typename T> using cast_op_type = type;
 
@@ -1826,7 +1824,7 @@ public:
     static constexpr bool has_kwargs = kwargs_pos < 0;
     static constexpr bool has_args = args_pos < 0;
 
-    static constexpr auto arg_names = detail::concat(make_caster<Args>::name...);
+    static constexpr auto arg_names = concat(type_descr(make_caster<Args>::name)...);
 
     bool load_args(function_call &call) {
         return load_impl_sequence(call, indices{});

include/pybind11/detail/init.h

@@ -24,7 +24,7 @@ public:
 
     template <typename> using cast_op_type = value_and_holder &;
     operator value_and_holder &() { return *value; }
-    static constexpr auto name = type_descr(_<value_and_holder>());
+    static constexpr auto name = _<value_and_holder>();
 
 private:
     value_and_holder *value = nullptr;

include/pybind11/eigen.h

@@ -185,7 +185,7 @@ template <typename Type_> struct EigenProps {
     static constexpr bool show_c_contiguous = show_order && requires_row_major;
     static constexpr bool show_f_contiguous = !show_c_contiguous && show_order && requires_col_major;
 
-    static constexpr auto descriptor = type_descr(
+    static constexpr auto descriptor =
         _("numpy.ndarray[") + npy_format_descriptor<Scalar>::name +
         _("[")  + _<fixed_rows>(_<(size_t) rows>(), _("m")) +
         _(", ") + _<fixed_cols>(_<(size_t) cols>(), _("n")) +
@@ -199,8 +199,7 @@ template <typename Type_> struct EigenProps {
         _<show_writeable>(", flags.writeable", "") +
         _<show_c_contiguous>(", flags.c_contiguous", "") +
         _<show_f_contiguous>(", flags.f_contiguous", "") +
-        _("]")
-    );
+        _("]");
 };
 
 // Casts an Eigen type to numpy array.  If given a base, the numpy array references the src data,

include/pybind11/functional.h

@@ -75,7 +75,7 @@ public:
             return cpp_function(std::forward<Func>(f_), policy).release();
     }
 
-    PYBIND11_TYPE_CASTER(type, _("Callable[[") + argument_loader<Args...>::arg_names + _("], ")
+    PYBIND11_TYPE_CASTER(type, _("Callable[[") + concat(make_caster<Args>::name...) + _("], ")
                                + make_caster<retval_type>::name + _("]"));
 };
 

include/pybind11/pybind11.h

@@ -217,34 +217,30 @@ protected:
 
         /* Generate a proper function signature */
         std::string signature;
-        size_t type_depth = 0, char_index = 0, type_index = 0, arg_index = 0;
-        while (true) {
-            char c = text[char_index++];
-            if (c == '\0')
-                break;
+        size_t type_index = 0, arg_index = 0;
+        for (auto *pc = text; *pc != '\0'; ++pc) {
+            const auto c = *pc;
 
             if (c == '{') {
-                // Write arg name for everything except *args, **kwargs and return type.
-                if (type_depth == 0 && text[char_index] != '*' && arg_index < args) {
-                    if (!rec->args.empty() && rec->args[arg_index].name) {
-                        signature += rec->args[arg_index].name;
-                    } else if (arg_index == 0 && rec->is_method) {
-                        signature += "self";
-                    } else {
-                        signature += "arg" + std::to_string(arg_index - (rec->is_method ? 1 : 0));
-                    }
-                    signature += ": ";
+                // Write arg name for everything except *args and **kwargs.
+                if (*(pc + 1) == '*')
+                    continue;
+
+                if (arg_index < rec->args.size() && rec->args[arg_index].name) {
+                    signature += rec->args[arg_index].name;
+                } else if (arg_index == 0 && rec->is_method) {
+                    signature += "self";
+                } else {
+                    signature += "arg" + std::to_string(arg_index - (rec->is_method ? 1 : 0));
                 }
-                ++type_depth;
+                signature += ": ";
             } else if (c == '}') {
-                --type_depth;
-                if (type_depth == 0) {
-                    if (arg_index < rec->args.size() && rec->args[arg_index].descr) {
-                        signature += "=";
-                        signature += rec->args[arg_index].descr;
-                    }
-                    arg_index++;
+                // Write default value if available.
+                if (arg_index < rec->args.size() && rec->args[arg_index].descr) {
+                    signature += "=";
+                    signature += rec->args[arg_index].descr;
                 }
+                arg_index++;
             } else if (c == '%') {
                 const std::type_info *t = types[type_index++];
                 if (!t)
@@ -272,7 +268,7 @@ protected:
                 signature += c;
             }
         }
-        if (type_depth != 0 || types[type_index] != nullptr)
+        if (arg_index != args || types[type_index] != nullptr)
             pybind11_fail("Internal error while parsing type signature (2)");
 
 #if PY_MAJOR_VERSION < 3