Fix overflow exception in BitArray

spec/std/bit_array_spec.cr

@@ -246,6 +246,19 @@ describe "BitArray" do
 
       ba[28..40].should eq(from_int(13, 0b1111111111111))
     end
+
+    it "gets 32-bit boundaries" do
+      {32, 64, 128}.each do |ba_size|
+        ba = BitArray.new(ba_size, true)
+        {0, 31, 32}.each do |start|
+          {0, 31, 32}.each do |len|
+            size = {ba_size - start, len}.min
+            ba[start, len].size.should eq(size)
+            ba[start, len].should eq(BitArray.new(size, true))
+          end
+        end
+      end
+    end
   end
 
   it "toggles a bit" do

src/bit_array.cr

@@ -140,18 +140,18 @@ struct BitArray
       bits = @bits[0]
 
       bits >>= start
-      bits &= (1 << count) - 1
+      bits &= (1 << count) &- 1
 
       BitArray.new(count).tap { |ba| ba.@bits[0] = bits }
     elsif size <= 64
       # Original fits in int64, we can use bitshifts
       bits = @bits.as(UInt64*)[0]
 
       bits >>= start
-      bits &= (1 << count) - 1
+      bits &= (1 << count) &- 1
 
       if count <= 32
-        BitArray.new(count).tap { |ba| ba.@bits[0] = bits.to_u32 }
+        BitArray.new(count).tap { |ba| ba.@bits[0] = bits.to_u32! }
       else
         BitArray.new(count).tap { |ba| ba.@bits.as(UInt64*)[0] = bits }
       end
@@ -169,7 +169,7 @@ struct BitArray
         bits = @bits[start_bit_index + i + 1]
 
         high_bits = bits
-        high_bits &= (1 << start_sub_index) - 1
+        high_bits &= (1 << start_sub_index) &- 1
         high_bits <<= 32 - start_sub_index
 
         ba.@bits[i] = low_bits | high_bits