Merge pull request #423 from savi-lang/add/bytes-set-byte-at

Add `Bytes.set_byte_at!` method (and `Bytes.[]=!` synonym).

core/Bytes.savi

@@ -270,10 +270,16 @@
 
   :fun "[]!"(index): @byte_at!(index)
 
+  :fun ref "[]=!"(index, value): @set_byte_at!(index, value)
+
   :fun byte_at!(index USize)
     if (@size <= index) error!
     @_ptr._get_at(index)
 
+  :fun ref set_byte_at!(index USize, byte U8)
+    if (@size <= index) error!
+    @_ptr._assign_at(index, byte)
+
   :fun _offset_to_index(offset ISize) USize
     if (offset < 0) (offset.usize + @size | offset.usize)
 

spec/core/Bytes.Spec.savi

@@ -205,6 +205,12 @@
     assert: b"example"[3]! == 'm'
     assert error: b"example"[7]!
 
+  :it "assigns a new byte at the given byte offset"
+    bytes Bytes'ref = b"example".clone
+    assert: (bytes[3]! = 'M') == 'M'
+    assert error: bytes[7]! = '?'
+    assert: bytes == b"exaMple"
+
   :it "trims bytes off the start and end of the byte string"
     assert: b"example".trim(2)      == b"ample"
     assert: b"example".trim(3,  -2) == b"mp"