From ad37651726f5a12a387fbd1fc626a16c2cd62174 Mon Sep 17 00:00:00 2001
From: Daniel Lemire <lemire@gmail.com>
Date: Mon, 22 Feb 2021 16:54:47 -0500
Subject: [PATCH] Guarding undefined templates with a static_assert. (#1454)

* Guarding undefined templates with a static_assert.

* Fixing comments.

* Undeprecating (or whatever you want to call it).
---
 include/simdjson/dom/element.h               | 17 +++++++--------
 include/simdjson/generic/ondemand/document.h | 23 +++++++++++---------
 include/simdjson/generic/ondemand/value.h    |  9 +++++++-
 3 files changed, 29 insertions(+), 20 deletions(-)

diff --git a/include/simdjson/dom/element.h b/include/simdjson/dom/element.h
index eb33befe..49ae8618 100644
--- a/include/simdjson/dom/element.h
+++ b/include/simdjson/dom/element.h
@@ -198,14 +198,6 @@ public:
   simdjson_really_inline bool is() const noexcept;
 
   /**
-   * @private
-   * Deprecated as a public interface. These methods will be made private in a future
-   * release. Use get_double(), get_bool(), get_uint64(), get_int64(),
-   * get_object(), get_array() or get_string() instead.  We found in practice that
-   * the template would mislead users into writing get<X>() for types X that
-   * are not among the supported types (e.g., get<QString>(), get<std::string>(),
-   * get<short>()), and the resulting C++ compiler error is difficult to parse.
-   *
    * Get the value as the provided type (T).
    *
    * Supported types:
@@ -215,6 +207,9 @@ public:
    * - Array: dom::array
    * - Object: dom::object
    *
+   * You may use get_double(), get_bool(), get_uint64(), get_int64(),
+   * get_object(), get_array() or get_string() instead.
+   *
    * @tparam T bool, double, uint64_t, int64_t, std::string_view, const char *, dom::array, dom::object
    *
    * @returns The value cast to the given type, or:
@@ -222,7 +217,11 @@ public:
    */
 
   template<typename T>
-  inline simdjson_result<T> get() const noexcept;
+  inline simdjson_result<T> get() const noexcept {
+    // Unless the simdjson library provides an inline implementation, calling this method should
+    // immediately fail.
+    static_assert(!sizeof(T), "The get method with given type is not implemented by the simdjson library.");
+  }
 
   /**
    * Get the value as the provided type (T).
diff --git a/include/simdjson/generic/ondemand/document.h b/include/simdjson/generic/ondemand/document.h
index c86ee734..908ad0b6 100644
--- a/include/simdjson/generic/ondemand/document.h
+++ b/include/simdjson/generic/ondemand/document.h
@@ -100,24 +100,27 @@ public:
   simdjson_really_inline bool is_null() noexcept;
 
   /**
-   * @private
-   * Deprecated as a public interface. These methods will be made private in a future
-   * release. Use get_double(), get_bool(), get_uint64(), get_int64(),
-   * get_object(), get_array() or get_string() instead. We found in practice that
-   * the template would mislead users into writing get<X>() for types X that
-   * are not among the supported types (e.g., get<QString>(), get<std::string>(),
-   * get<short>()), and the resulting C++ compiler error is difficult to parse.
-   *
    * Get this value as the given type.
    *
    * Supported types: object, array, raw_json_string, string_view, uint64_t, int64_t, double, bool
    *
+   * You may use get_double(), get_bool(), get_uint64(), get_int64(),
+   * get_object(), get_array(), get_raw_json_string(), or get_string() instead.
+   *
    * @returns A value of the given type, parsed from the JSON.
    * @returns INCORRECT_TYPE If the JSON value is not the given type.
    */
-  template<typename T> simdjson_really_inline simdjson_result<T> get() & noexcept;
+  template<typename T> simdjson_really_inline simdjson_result<T> get() & noexcept {
+    // Unless the simdjson library provides an inline implementation, calling this method should
+    // immediately fail.
+    static_assert(!sizeof(T), "The get method with given type is not implemented by the simdjson library.");
+  }
   /** @overload template<typename T> simdjson_result<T> get() & noexcept */
-  template<typename T> simdjson_really_inline simdjson_result<T> get() && noexcept;
+  template<typename T> simdjson_really_inline simdjson_result<T> get() && noexcept {
+    // Unless the simdjson library provides an inline implementation, calling this method should
+    // immediately fail.
+    static_assert(!sizeof(T), "The get method with given type is not implemented by the simdjson library.");
+  }
 
   /**
    * Get this value as the given type.
diff --git a/include/simdjson/generic/ondemand/value.h b/include/simdjson/generic/ondemand/value.h
index fdeeafe1..2c50f139 100644
--- a/include/simdjson/generic/ondemand/value.h
+++ b/include/simdjson/generic/ondemand/value.h
@@ -27,10 +27,17 @@ public:
    *
    * Supported types: object, array, raw_json_string, string_view, uint64_t, int64_t, double, bool
    *
+   * You may use get_double(), get_bool(), get_uint64(), get_int64(),
+   * get_object(), get_array(), get_raw_json_string(), or get_string() instead.
+   *
    * @returns A value of the given type, parsed from the JSON.
    * @returns INCORRECT_TYPE If the JSON value is not the given type.
    */
-  template<typename T> simdjson_really_inline simdjson_result<T> get() noexcept;
+  template<typename T> simdjson_really_inline simdjson_result<T> get() noexcept {
+    // Unless the simdjson library provides an inline implementation, calling this method should
+    // immediately fail.
+    static_assert(!sizeof(T), "The get method with given type is not implemented by the simdjson library.");
+  }
 
   /**
    * Get this value as the given type.