From 3bd1fb82ba12b95ddf8f7bde5e511dad848716eb Mon Sep 17 00:00:00 2001
From: Alexander Petrov <alldroll@gmail.com>
Date: Fri, 12 Jun 2020 19:42:02 +0100
Subject: [PATCH] Throw an error on negative shifts (#421)

Throw an error on negative shifts
---
 builtins.go                     | 16 +++++++++-------
 testdata/bitwise_shift4.golden  | 11 ++++++++++-
 testdata/bitwise_shift5.golden  |  1 +
 testdata/bitwise_shift5.jsonnet |  2 ++
 testdata/bitwise_shift6.golden  | 10 ++++++++++
 testdata/bitwise_shift6.jsonnet |  1 +
 6 files changed, 33 insertions(+), 8 deletions(-)
 create mode 100644 testdata/bitwise_shift5.golden
 create mode 100644 testdata/bitwise_shift5.jsonnet
 create mode 100644 testdata/bitwise_shift6.golden
 create mode 100644 testdata/bitwise_shift6.jsonnet

diff --git a/builtins.go b/builtins.go
index 87c8fe5..acb20b8 100644
--- a/builtins.go
+++ b/builtins.go
@@ -844,7 +844,7 @@ var builtinExponent = liftNumeric(func(f float64) float64 {
 	return float64(exponent)
 })
 
-func liftBitwise(f func(int64, int64) int64) func(*interpreter, traceElement, value, value) (value, error) {
+func liftBitwise(f func(int64, int64) int64, positiveRightArg bool) func(*interpreter, traceElement, value, value) (value, error) {
 	return func(i *interpreter, trace traceElement, xv, yv value) (value, error) {
 		x, err := i.getNumber(xv, trace)
 		if err != nil {
@@ -862,16 +862,18 @@ func liftBitwise(f func(int64, int64) int64) func(*interpreter, traceElement, va
 			msg := fmt.Sprintf("Bitwise operator argument %v outside of range [%v, %v]", y.value, int64(math.MinInt64), int64(math.MaxInt64))
 			return nil, makeRuntimeError(msg, i.getCurrentStackTrace(trace))
 		}
+		if positiveRightArg && y.value < 0 {
+			return nil, makeRuntimeError("Shift by negative exponent.", i.getCurrentStackTrace(trace))
+		}
 		return makeDoubleCheck(i, trace, float64(f(int64(x.value), int64(y.value))))
 	}
 }
 
-// TODO(sbarzowski) negative shifts
-var builtinShiftL = liftBitwise(func(x, y int64) int64 { return x << uint(y%64) })
-var builtinShiftR = liftBitwise(func(x, y int64) int64 { return x >> uint(y%64) })
-var builtinBitwiseAnd = liftBitwise(func(x, y int64) int64 { return x & y })
-var builtinBitwiseOr = liftBitwise(func(x, y int64) int64 { return x | y })
-var builtinBitwiseXor = liftBitwise(func(x, y int64) int64 { return x ^ y })
+var builtinShiftL = liftBitwise(func(x, y int64) int64 { return x << uint(y%64) }, true)
+var builtinShiftR = liftBitwise(func(x, y int64) int64 { return x >> uint(y%64) }, true)
+var builtinBitwiseAnd = liftBitwise(func(x, y int64) int64 { return x & y }, false)
+var builtinBitwiseOr = liftBitwise(func(x, y int64) int64 { return x | y }, false)
+var builtinBitwiseXor = liftBitwise(func(x, y int64) int64 { return x ^ y }, false)
 
 func builtinObjectFieldsEx(i *interpreter, trace traceElement, objv, includeHiddenV value) (value, error) {
 	obj, err := i.getObject(objv, trace)
diff --git a/testdata/bitwise_shift4.golden b/testdata/bitwise_shift4.golden
index 573541a..96859c3 100644
--- a/testdata/bitwise_shift4.golden
+++ b/testdata/bitwise_shift4.golden
@@ -1 +1,10 @@
-0
+RUNTIME ERROR: Shift by negative exponent.
+-------------------------------------------------
+	testdata/bitwise_shift4:1:1-15	$
+
+10000 >> (-10)
+
+-------------------------------------------------
+	During evaluation	
+
+
diff --git a/testdata/bitwise_shift5.golden b/testdata/bitwise_shift5.golden
new file mode 100644
index 0000000..ff1352d
--- /dev/null
+++ b/testdata/bitwise_shift5.golden
@@ -0,0 +1 @@
+1099511627776
diff --git a/testdata/bitwise_shift5.jsonnet b/testdata/bitwise_shift5.jsonnet
new file mode 100644
index 0000000..5be2236
--- /dev/null
+++ b/testdata/bitwise_shift5.jsonnet
@@ -0,0 +1,2 @@
+/* 1 << (1000 % 64) */
+1 << 1000
diff --git a/testdata/bitwise_shift6.golden b/testdata/bitwise_shift6.golden
new file mode 100644
index 0000000..f68c6bf
--- /dev/null
+++ b/testdata/bitwise_shift6.golden
@@ -0,0 +1,10 @@
+RUNTIME ERROR: Shift by negative exponent.
+-------------------------------------------------
+	testdata/bitwise_shift6:1:1-13	$
+
+1 << (0 - 1)
+
+-------------------------------------------------
+	During evaluation	
+
+
diff --git a/testdata/bitwise_shift6.jsonnet b/testdata/bitwise_shift6.jsonnet
new file mode 100644
index 0000000..3a794c8
--- /dev/null
+++ b/testdata/bitwise_shift6.jsonnet
@@ -0,0 +1 @@
+1 << (0 - 1)