From 1bdcb6ffdf92382597706ca1f0a2bc4c22d80b77 Mon Sep 17 00:00:00 2001
From: Oskar Eichler <62393985+OskarEichler@users.noreply.github.com>
Date: Sat, 29 Aug 2026 18:41:50 +0200
Subject: [PATCH 1/2] Isolate mutable state in copied environments

---
 lib/rbs/environment.rb              | 3 ++-
 lib/rbs/environment/class_entry.rb  | 4 ++++
 lib/rbs/environment/module_entry.rb | 4 ++++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/lib/rbs/environment.rb b/lib/rbs/environment.rb
index 0fb4347142..777e46de31 100644
--- a/lib/rbs/environment.rb
+++ b/lib/rbs/environment.rb
@@ -58,12 +58,13 @@ def initialize
 
     def initialize_copy(other)
       @sources = other.sources.dup
-      @class_decls = other.class_decls.dup
+      @class_decls = other.class_decls.transform_values(&:dup)
       @interface_decls = other.interface_decls.dup
       @type_alias_decls = other.type_alias_decls.dup
       @constant_decls = other.constant_decls.dup
       @global_decls = other.global_decls.dup
       @class_alias_decls = other.class_alias_decls.dup
+      @normalize_module_name_cache = other.instance_variable_get(:@normalize_module_name_cache).dup
     end
 
     def self.from_loader(loader)
diff --git a/lib/rbs/environment/class_entry.rb b/lib/rbs/environment/class_entry.rb
index 73762330a5..cff8ad87e0 100644
--- a/lib/rbs/environment/class_entry.rb
+++ b/lib/rbs/environment/class_entry.rb
@@ -12,6 +12,10 @@ def initialize(name)
         @context_decls = []
       end
 
+      def initialize_copy(other)
+        @context_decls = other.context_decls.dup
+      end
+
       def <<(context_decl)
         context_decls << context_decl
         @primary_decl = nil
diff --git a/lib/rbs/environment/module_entry.rb b/lib/rbs/environment/module_entry.rb
index 1f65cf4905..71bda093d0 100644
--- a/lib/rbs/environment/module_entry.rb
+++ b/lib/rbs/environment/module_entry.rb
@@ -12,6 +12,10 @@ def initialize(name)
         @context_decls = []
       end
 
+      def initialize_copy(other)
+        @context_decls = other.context_decls.dup
+      end
+
       def <<(context_decl)
         context_decls << context_decl
         self

From d9933ddf46aa4dc6084c668213f010416463bc0d Mon Sep 17 00:00:00 2001
From: Oskar Eichler <62393985+OskarEichler@users.noreply.github.com>
Date: Sat, 29 Aug 2026 18:51:39 +0200
Subject: [PATCH 2/2] Satisfy environment copy typecheck

---
 lib/rbs/environment/class_entry.rb  | 1 +
 lib/rbs/environment/module_entry.rb | 1 +
 2 files changed, 2 insertions(+)

diff --git a/lib/rbs/environment/class_entry.rb b/lib/rbs/environment/class_entry.rb
index cff8ad87e0..03fe326dc1 100644
--- a/lib/rbs/environment/class_entry.rb
+++ b/lib/rbs/environment/class_entry.rb
@@ -14,6 +14,7 @@ def initialize(name)
 
       def initialize_copy(other)
         @context_decls = other.context_decls.dup
+        self
       end
 
       def <<(context_decl)
diff --git a/lib/rbs/environment/module_entry.rb b/lib/rbs/environment/module_entry.rb
index 71bda093d0..47356c1b2a 100644
--- a/lib/rbs/environment/module_entry.rb
+++ b/lib/rbs/environment/module_entry.rb
@@ -14,6 +14,7 @@ def initialize(name)
 
       def initialize_copy(other)
         @context_decls = other.context_decls.dup
+        self
       end
 
       def <<(context_decl)