If they allowed FORTH it would be even worse -- everything in FORTH is redefinable -- you could make 1 equal to 2 if you want.
https://www.forth.com/embedded/#Annotated_example_source_cod... contains a version of the canonical washing machine program.
\ Top-level control
: WASHER ( -- ) WASH SPIN RINSE SPIN ;
$ irb
2.4.1 :001 > 1.class
=> Integer
2.4.1 :002 > class Integer
2.4.1 :003?> def 1
2.4.1 :004?> 2
2.4.1 :005?> end
2.4.1 :006?> end
SyntaxError: (irb):3: syntax error, unexpected tINTEGER
def 1
^
(irb):6: syntax error, unexpected keyword_end, expecting end-of-input
More evidence:
2.4.1 :001 > class Integer
2.4.1 :002?> define_method(:one) { 1 }
2.4.1 :003?> end
=> :one
2.4.1 :004 > Integer.one
NoMethodError: undefined method `one' for Integer:Class
2.4.1 :005 > Integer.new.one
NoMethodError: undefined method `new' for Integer:Class
2.4.1 :006 > Integer.new
NoMethodError: undefined method `new' for Integer:Class
2.4.1 :007 > class Klass
2.4.1 :008?> define_method(:one) { 1 }
2.4.1 :009?> end
=> :one
2.4.1 :010 > Klass.one
NoMethodError: undefined method `one' for XY:Class
2.4.1 :011 > Klass.new.one
=> 1
TLDR MRI gets the value of the number directly from value of the C pointer and saves the lookup. It's a 1 in the lowest bit and the integer value in the others. That's why 0.object_id == 1, 1.object_id == 3, etc
Obviously that's implementation dependent but I guess no Ruby implementation is going us to redefine integers if MRI does not.