Problem

Prism parser was not properly enforcing eval isolation in Ractors. Tests were added to verify eval behavior in Ractor isolation contexts. Test eval with outer locals in a Ractor raises SyntaxError failed with Prism but passed with parse.y.

Tests Added

Three new test cases were added to verify eval isolation behavior in Ractors:

1. eval with outer locals in a Ractor raises SyntaxError [Bug #22883]
2. eval of an undefined name in a Ractor raises NameError
3. eval of a local defined inside the Ractor works

Behavior Before Fix

With parse.y (legacy parser):

Driver is ruby 3.5.0dev (2025-10-22T16:07:26Z master 839b1fa54f) [x86_64-linux]
Target is ruby 3.5.0dev (2025-10-22T16:07:26Z master 839b1fa54f) [x86_64-linux]

test_ractor.rb  PASS 143

Finished in 4.07 sec

PASS all 143 tests

With Prism (default) - BEFORE FIX:

Driver is ruby 3.5.0dev (2025-10-22T16:07:26Z master 839b1fa54f) +PRISM [x86_64-linux]
Target is ruby 3.5.0dev (2025-10-22T16:07:26Z master 839b1fa54f) +PRISM [x86_64-linux]

#51 test_ractor.rb:759: 
     outer = 42
     r = Ractor.new do
       eval("outer")
     end
     begin
       r.value
     rescue Ractor::RemoteError => e
       e.cause.class
     end
  #=> "false" (expected "SyntaxError")  
test_ractor.rb  FAIL 1/143

Finished in 3.71 sec

FAIL 1/143 tests failed

Solution

Added helper functions to compute isolation depth consistently across both parsers:

• compute_isolated_depth_from_ep(): Walks the environment stack to detect if eval is inside an isolated context
• compute_isolated_depth_from_block(): Convenience wrapper that extracts EP from a block

Both pm_eval_make_iseq() (Prism) and eval_make_iseq() (parse.y) now use the same isolation detection logic.

Testing After Fix

With Prism - AFTER FIX:

Driver is ruby 3.5.0dev (2025-10-22T16:07:26Z master 839b1fa54f) +PRISM [x86_64-linux]
Target is ruby 3.5.0dev (2025-10-22T16:07:26Z master 839b1fa54f) +PRISM [x86_64-linux]

test_ractor.rb  PASS 143

Finished in 4.29 sec

PASS all 143 tests

Test eval with outer locals in a Ractor raises SyntaxError now correctly raises SyntaxError when eval tries to access outer locals in a Ractor. Both parsers produce identical behavior.

Root Cause

Prism was hardcoding 0 for isolated_depth when compiling eval, while parse.y was correctly detecting the isolation context. The fix ensures both parsers use the same detection mechanism.