doc: document implementation-specific limits on numeric domain of bitwise operations

Author: johnbartholomew

doc/ref/language.html.md

@@ -135,6 +135,8 @@ Jsonnet numbers are 64-bit floating point numbers as defined in IEEE754 excludin
 
 Integers can be safely represented as a Jsonnet number in the range [-2^53 + 1,2^53 - 1]. This is [a direct consequence of IEEE754 spec](https://en.wikipedia.org/wiki/Double-precision_floating-point_format), with the requirements that a safe integer is representable exactly, and cannot be produced by rounding any other integer to fit the IEEE-754 representation. See also, the JavaScript [`Number.MAX_SAFE_INTEGER`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER), [`Number.MIN_SAFE_INTEGER`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MIN_SAFE_INTEGER), and [`Number.isSafeInteger`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isSafeInteger) definitions.
 
+Currently, the C++ and Go Jsonnet implementations restrict the arguments (inputs) to binary bitwise operations (the operators `<<`, `>>`, `&`, `|`, and `^`) to the safe integer range.
+
 ### Function
 
 Functions in Jsonnet are functions in the mathematical sense. Each function has parameters and a body expression. The result of calling a function is equivalent to the result of evaluating its body with arguments introduced to the environment.

doc/ref/spec.html

@@ -2826,6 +2826,8 @@ <h4 id="execution">Execution</h4>
           standard way, then convert back to IEEE double precision floating point. In shift
           operations <code>&lt;&lt;</code>, <code>&gt;&gt;</code>, the right hand value modulo 64 is
           interpreted as the shift count. Shifting with a negative shift count raises an error.
+          Individiual Jsonnet implementations may place further restrictions on the range of inputs
+          or outputs to bitwise operations.
         </li>
         <li>
           <b>Standard functions</b>: The following functions have standard mathematical behavior