I'm trying to untangle this a bit so I understand the change. I'd like to better understand and document the conditions where a CallBase is potentiallyRefined but does not have a RefinedCachingCallSite.

This fix works but only repairs the interpreter. JIT mode needs additional help to clear out already-compiled code when the scope's refinements are changed.

[] jruby $ jruby blah.rb
NoMethodError: undefined method 'indent' for an instance of String
  indent_normal at blah.rb:9
         <main> at blah.rb:19
    module_exec at org/jruby/RubyModule.java:4247
     initialize at org/jruby/RubyModule.java:3432
            new at org/jruby/RubyClass.java:1050
         <main> at blah.rb:13
[] jruby $ jruby -X-C blah.rb
"   foo"

I'm working on some additional patches on top of this PR.

Interpreter and JIT can be fixed by having the import clear out old compile code, as @evaniainbrooks did for fullInterpreterContext and as we can do by resetting the callCount and actualMethod in AbstractIRMethod and MixedModeIRMethod, but methods compiled eagerly at boot (CompiledIRMethod) don't have any way to recompile. In order to make them work with this we need to finally make all dynamic call sites in the JIT refinable.

I also observed that the changes in CallBase don't appear to trigger for the startup interpreter, likely because the sites passing in unrefined CallSite instances are only produced by the full interpreter. I'm going to see if I can clean up those paths so this logic can just be removed (if a call should be refined, we should not be passing in unrefined call sites and having to fix them up in the constructor).

I've pushed some additional changes as #9248, which fixes the JIT issue and eliminates the call site fix-up logic. The CompiledIRMethod issue will take a larger project to fix.

I will merge this PR and then my additional fixes. I'll open a separate issue for the CompiledIRMethod issues with changing refinement status.