maint(clang-tidy): Enable cpp-coreguideline slicing checks (#3210)

* maint(clang-tidy): add a clang-tidy slicing check

* Add self + touch up readme

* Fix typo

.clang-tidy

@@ -3,6 +3,7 @@ FormatStyle: file
 Checks: '
 *bugprone*,
 cppcoreguidelines-init-variables,
+cppcoreguidelines-slicing,
 clang-analyzer-optin.cplusplus.VirtualCall,
 llvm-namespace-comment,
 misc-misplaced-const,

README.rst

@@ -134,7 +134,7 @@ About
 This project was created by `Wenzel
 Jakob <http://rgl.epfl.ch/people/wjakob>`_. Significant features and/or
 improvements to the code were contributed by Jonas Adler, Lori A. Burns,
-Sylvain Corlay, Eric Cousineau, Ralf Grosse-Kunstleve, Trent Houliston, Axel
+Sylvain Corlay, Eric Cousineau, Aaron Gokaslan, Ralf Grosse-Kunstleve, Trent Houliston, Axel
 Huebl, @hulucc, Yannick Jadoul, Sergey Lyskov Johan Mabille, Tomasz Miąsko,
 Dean Moldovan, Ben Pritchard, Jason Rhinelander, Boris Schäling, Pim
 Schellart, Henry Schreiner, Ivan Smirnov, Boris Staletic, and Patrick Stewart.

include/pybind11/pybind11.h

@@ -1664,7 +1664,7 @@ inline str enum_name(handle arg) {
 }
 
 struct enum_base {
-    enum_base(handle base, handle parent) : m_base(base), m_parent(parent) { }
+    enum_base(const handle &base, const handle &parent) : m_base(base), m_parent(parent) { }
 
     PYBIND11_NOINLINE void init(bool is_arithmetic, bool is_convertible) {
         m_base.attr("__entries") = dict();