BUG: missing downcast_distinct from String to OptionParser (Crystal::NonGenericClassType to Crystal::NonGenericClassType)

[philipp-classen]

The following program fails in the interpreter:

require "option_parser"

opt_parser = OptionParser.parse do |parser|
  parser.on("-h", "--help", "Show help") do
    puts parser
    exit
  end
end

parser = ""

I think, it is because the parser variable is used both in the block, but also reused as a different type (outside of the block). In the normal compiler, it works.

$ crystal i example.cr 
Crystal interpreter 1.16.0-dev [9b7fd8dc1] (2025-02-14).
EXPERIMENTAL SOFTWARE: if you find a bug, please consider opening an issue in
https://github.com/crystal-lang/crystal/issues/new/
In example.cr:3:27

 3 | opt_parser = OptionParser.parse do |parser|
                               ^----
Error: BUG: missing downcast_distinct from String to OptionParser (Crystal::NonGenericClassType to Crystal::NonGenericClassType)


In example.cr:4:3

 4 | parser.on("-h", "--help", "Show help") do
     ^-----
Error: BUG: missing downcast_distinct from String to OptionParser (Crystal::NonGenericClassType to Crystal::NonGenericClassType)

Can be reproduced with 1.15.1, but also with master:

$ crystal -v
Crystal 1.16.0-dev [9b7fd8dc1] (2025-02-14)

The compiler was not built in release mode.

LLVM: 19.1.7
Default target: x86_64-pc-linux-gnu

OS: Arch Linux

[straight-shoota]

Similar previous downcast bugs in the interpreter: #12283, #12532, #12342
I presume the fix could be similar to one of these.