[clang-tools-extra] [clang-tidy] Add modernize-use-std-format check (PR #90397)

[Mike Crowe via cfe-commits]

================
@@ -0,0 +1,84 @@
+.. title:: clang-tidy - modernize-use-std-format
+
+modernize-use-std-format
+========================
+
+Converts calls to ``absl::StrFormat``, or other functions via
+configuration options, to C++20's ``std::format``, or another function
+via a configuration option, modifying the format string appropriately and
+removing now-unnecessary calls to ``std::string::c_str()`` and
+``std::string::data()``.
+
+For example, it turns lines like
+
+.. code-block:: c++
+
+  return absl::StrFormat("The %s is %3d", description.c_str(), value);
+
+into:
+
+.. code-block:: c++
+
+  return std::format("The {} is {:3}", description, value);
+
+The check uses the same format-string-conversion algorithm as
+`modernize-use-std-print <../modernize/use-std-print.html>`_ and its
+shortcomings are described in the documentation for that check.
+
+Options
+-------
+
+.. option:: StrictMode
+
+   When `true`, the check will add casts when converting from variadic
+   functions and printing signed or unsigned integer types (including
+   fixed-width integer types from ``<cstdint>``, ``ptrdiff_t``, ``size_t``
+   and ``ssize_t``) as the opposite signedness to ensure that the output
+   would matches that of a simple wrapper for ``std::sprintf`` that
+   accepted a C-style variable argument list. For example, with
+   `StrictMode` enabled,
+
+  .. code-block:: c++
+
+    extern std::string strprintf(const char *format, ...);
+    int i = -42;
+    unsigned int u = 0xffffffff;
+    return strprintf("%d %u\n", i, u);
+
+  would be converted to
+
+  .. code-block:: c++
+
+    return std::format("{} {}\n", static_cast<unsigned int>(i), static_cast<int>(u));
+
+  to ensure that the output will continue to be the unsigned representation
+  of -42 and the signed representation of 0xffffffff (often 4294967254
+  and -1 respectively). When `false` (which is the default), these casts
+  will not be added which may cause a change in the output. Note that this
+  option makes no difference for the default value of
+  `StrFormatLikeFunctions` since ``absl::StrFormat`` takes a function
+  parameter pack and is not a variadic function.
+
+.. option:: StrFormatLikeFunctions
+
+   A semicolon-separated list of (fully qualified) extra function names to
----------------
mikecrowe wrote:

True. I'll fix that.

https://github.com/llvm/llvm-project/pull/90397