Bugfix lshift() bit overflow; close #3023

src/numeric.c

@@ -821,7 +821,8 @@ static mrb_value
 lshift(mrb_state *mrb, mrb_int val, mrb_int width)
 {
   mrb_assert(width > 0);
-  if (width > NUMERIC_SHIFT_WIDTH_MAX) {
+  if ((width > NUMERIC_SHIFT_WIDTH_MAX) ||
+      (val   > (MRB_INT_MAX >> width))) {
     mrb_float f = (mrb_float)val;
     while (width--) {
       f *= 2;

test/t/integer.rb

@@ -147,6 +147,9 @@ assert('Integer#<<', '15.2.8.3.12') do
 
   # Left Shift by a negative is Right Shift
   assert_equal 23, 46 << -1
+
+  # Left Shift by 31 is bitShift overflow to SignedInt
+  assert_equal 2147483648, 1 << 31
 end
 
 assert('Integer#>>', '15.2.8.3.13') do