fix: mask left shifts in numeric fast path

Motivation:
Jsonnet interprets shift counts modulo 64, but the numeric fast path validated
left shifts using the unmasked count. Expressions routed through outer
arithmetic could therefore fail even when the generic evaluator succeeded.

Modification:
Normalize non-negative left-shift counts modulo 64 before both overflow
validation and execution, and add regressions for counts 64, 65, and 128.

Result:
Numeric fast-path behavior now matches the generic evaluator, go-jsonnet,
jrsonnet, and the Jsonnet specification without changing valid count-65
behavior.

References:
- #1096
- https://jsonnet.org/ref/spec.html

Author: He-Pin

sjsonnet/src/sjsonnet/Evaluator.scala

@@ -894,9 +894,10 @@ class Evaluator(
         val ll = visitExprAsDouble(e.lhs).toSafeLong(pos)
         val rr = visitExprAsDouble(e.rhs).toSafeLong(pos)
         if (rr < 0) Error.fail("Shift by negative exponent", pos)
-        if (rr >= 1 && math.abs(ll) >= (1L << (63 - rr)))
+        val masked = (rr % 64).toInt
+        if (masked >= 1 && math.abs(ll) >= (1L << (63 - masked)))
           Error.fail("Numeric value outside safe integer range for bitwise operation", pos)
-        (ll << rr).toDouble
+        (ll << masked).toDouble
       case Expr.BinaryOp.OP_>> =>
         val ll = visitExprAsDouble(e.lhs).toSafeLong(pos)
         val rr = visitExprAsDouble(e.rhs).toSafeLong(pos)

sjsonnet/test/resources/new_test_suite/leftshift_fast_path_masking.jsonnet

@@ -0,0 +1,6 @@
+std.assertEqual((1 << 64) * 1, 1) &&
+std.assertEqual(((1 << 64) + 0) * 1, 1) &&
+std.assertEqual((1 << 65) * 1, 2) &&
+std.assertEqual((1 << 128) * 1, 1) &&
+std.assertEqual((0 << 128) * 1, 0) &&
+true

sjsonnet/test/resources/new_test_suite/leftshift_fast_path_masking.jsonnet.golden

@@ -0,0 +1 @@
+true