Bug 1609943 - Split guideline on unary operators into C++ and JavaScript part. r=sylvestre

C++: Remove reference to JavaScript typeof from 'Operators' section and specifically refer to sizeof only.

JavaScript: Added remainder of the guideline referring to typeof.

Differential Revision: https://phabricator.services.mozilla.com/D60261

--HG--
extra : moz-landing-system : lando

tools/lint/docs/coding-style/coding_style_cpp.rst

@@ -242,8 +242,8 @@ is doing, without needing to further examine base classes.
 Operators
 ~~~~~~~~~
 
-Unary keyword operators, such as ``typeof`` and ``sizeof``, should have
+The unary keyword operator ``sizeof``, should have its operand parenthesized
-their operand parenthesized; e.g. ``typeof("foo") == "string"``.
+even if it is an expression; e.g. ``int8_t arr[64]; memset(arr, 42, sizeof(arr));``.
 
 
 Literals

tools/lint/docs/coding-style/coding_style_js.rst

@@ -66,6 +66,8 @@ line, in long member expression.
 
 In JavaScript, ``==`` is preferred to ``===``.
 
+Unary keyword operators, such as ``typeof``, should have their operand
+parenthesized; e.g. ``typeof("foo") == "string"``.
 
 Literals
 ~~~~~~~~