interp: fix derivation of type of slice expression of binary object

Fixes #1328.

_test/issue-1328.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+	"crypto/sha1"
+	"encoding/hex"
+)
+
+func main() {
+	script := "hello"
+	sumRaw := sha1.Sum([]byte(script))
+	sum := hex.EncodeToString(sumRaw[:])
+	println(sum)
+}
+
+// Output:
+// aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d

interp/type.go

@@ -854,6 +854,14 @@ func nodeType2(interp *Interpreter, sc *scope, n *node, seen []*node) (t *itype,
 		if err != nil {
 			return nil, err
 		}
+
+		if t.cat == valueT {
+			switch t.rtype.Kind() {
+			case reflect.Array, reflect.Ptr:
+				t = valueTOf(reflect.SliceOf(t.rtype.Elem()), withScope(sc))
+			}
+			break
+		}
 		if t.cat == ptrT {
 			t = t.val
 		}