More accurately model Class types

Author: st0012

zjit/src/hir_type/gen_hir_type.rb

@@ -74,8 +74,9 @@ def base_type name
 base_type "Range"
 base_type "Set"
 base_type "Regexp"
-base_type "Class"
-base_type "Module"
+_, module_exact = base_type "Module"
+module_exact.subtype "Class"
+module_exact.subtype "ClassExact"
 
 (integer, integer_exact) = base_type "Integer"
 # CRuby partitions Integer into immediate and non-immediate variants.