ZJIT: Fix incorrect self.class.respond_to? folding (#15001)

Right now we have a subtle type system bug around `types::Class`. Until
that is resolved, stop marking `Kernel#class` as returning
`types::Class`, which fixes Rubocop.

Re: https://github.com/Shopify/ruby/issues/850

3 files changed, 90 insertions, 4 deletions

diff --git a/zjit/src/cruby_methods.rs b/zjit/src/cruby_methods.rs
index 12d226ce51..bd3409ff07 100644
--- a/zjit/src/cruby_methods.rs
+++ b/zjit/src/cruby_methods.rs
@@ -231,7 +231,9 @@ pub fn init() -> Annotations {
 
     annotate_builtin!(rb_mKernel, "Float", types::Float);
     annotate_builtin!(rb_mKernel, "Integer", types::Integer);
-    annotate_builtin!(rb_mKernel, "class", types::Class, leaf);
+    // TODO(max): Annotate rb_mKernel#class as returning types::Class. Right now there is a subtle
+    // type system bug that causes an issue if we make it return types::Class.
+    annotate_builtin!(rb_mKernel, "class", types::HeapObject, leaf);
     annotate_builtin!(rb_mKernel, "frozen?", types::BoolExact);
     annotate_builtin!(rb_cSymbol, "name", types::StringExact);
     annotate_builtin!(rb_cSymbol, "to_s", types::StringExact);
diff --git a/zjit/src/hir/opt_tests.rs b/zjit/src/hir/opt_tests.rs
index c7764bd290..d697065da9 100644
--- a/zjit/src/hir/opt_tests.rs
+++ b/zjit/src/hir/opt_tests.rs
@@ -2358,7 +2358,7 @@ mod hir_opt_tests {
           PatchPoint MethodRedefined(Module@0x1010, class@0x1018, cme:0x1020)
           PatchPoint NoSingletonClass(Module@0x1010)
           IncrCounter inline_iseq_optimized_send_count
-          v26:Class = InvokeBuiltin leaf _bi20, v21
+          v26:HeapObject = InvokeBuiltin leaf _bi20, v21
           CheckInterrupts
           Return v26
         ");
@@ -7050,4 +7050,88 @@ mod hir_opt_tests {
           Return v19
         ");
     }
+
+    #[test]
+    fn test_fold_self_class_respond_to_true() {
+        eval(r#"
+            class C
+              class << self
+                attr_accessor :_lex_actions
+                private :_lex_actions, :_lex_actions=
+              end
+              self._lex_actions = [1, 2, 3]
+              def initialize
+                if self.class.respond_to?(:_lex_actions, true)
+                  :CORRECT
+                else
+                  :oh_no_wrong
+                end
+              end
+            end
+            C.new  # warm up
+            TEST = C.instance_method(:initialize)
+        "#);
+        assert_snapshot!(hir_string_proc("TEST"), @r"
+        fn initialize@<compiled>:9:
+        bb0():
+          EntryPoint interpreter
+          v1:BasicObject = LoadSelf
+          Jump bb2(v1)
+        bb1(v4:BasicObject):
+          EntryPoint JIT(0)
+          Jump bb2(v4)
+        bb2(v6:BasicObject):
+          PatchPoint MethodRedefined(C@0x1000, class@0x1008, cme:0x1010)
+          PatchPoint NoSingletonClass(C@0x1000)
+          v40:HeapObject[class_exact:C] = GuardType v6, HeapObject[class_exact:C]
+          IncrCounter inline_iseq_optimized_send_count
+          v43:HeapObject = InvokeBuiltin leaf _bi20, v40
+          v12:StaticSymbol[:_lex_actions] = Const Value(VALUE(0x1038))
+          v13:TrueClass = Const Value(true)
+          PatchPoint MethodRedefined(Class@0x1040, respond_to?@0x1048, cme:0x1050)
+          PatchPoint NoSingletonClass(Class@0x1040)
+          v47:ModuleSubclass[class_exact*:Class@VALUE(0x1040)] = GuardType v43, ModuleSubclass[class_exact*:Class@VALUE(0x1040)]
+          PatchPoint MethodRedefined(Class@0x1040, _lex_actions@0x1078, cme:0x1080)
+          PatchPoint NoSingletonClass(Class@0x1040)
+          v51:TrueClass = Const Value(true)
+          IncrCounter inline_cfunc_optimized_send_count
+          CheckInterrupts
+          v22:StaticSymbol[:CORRECT] = Const Value(VALUE(0x10a8))
+          CheckInterrupts
+          Return v22
+        ");
+    }
+
+    #[test]
+    fn test_fold_self_class_name() {
+        eval(r#"
+            class C; end
+            def test(o) = o.class.name
+            test(C.new)
+        "#);
+        assert_snapshot!(hir_string("test"), @r"
+        fn test@<compiled>:3:
+        bb0():
+          EntryPoint interpreter
+          v1:BasicObject = LoadSelf
+          v2:BasicObject = GetLocal l0, SP@4
+          Jump bb2(v1, v2)
+        bb1(v5:BasicObject, v6:BasicObject):
+          EntryPoint JIT(0)
+          Jump bb2(v5, v6)
+        bb2(v8:BasicObject, v9:BasicObject):
+          PatchPoint MethodRedefined(C@0x1000, class@0x1008, cme:0x1010)
+          PatchPoint NoSingletonClass(C@0x1000)
+          v24:HeapObject[class_exact:C] = GuardType v9, HeapObject[class_exact:C]
+          IncrCounter inline_iseq_optimized_send_count
+          v27:HeapObject = InvokeBuiltin leaf _bi20, v24
+          PatchPoint MethodRedefined(Class@0x1038, name@0x1040, cme:0x1048)
+          PatchPoint NoSingletonClass(Class@0x1038)
+          v31:ModuleSubclass[class_exact*:Class@VALUE(0x1038)] = GuardType v27, ModuleSubclass[class_exact*:Class@VALUE(0x1038)]
+          IncrCounter inline_cfunc_optimized_send_count
+          v33:StringExact|NilClass = CCall name@0x1070, v31
+          CheckInterrupts
+          Return v33
+        ");
+    }
 }
diff --git a/zjit/src/hir/tests.rs b/zjit/src/hir/tests.rs
index df14ba5a7c..32c71dc5d3 100644
--- a/zjit/src/hir/tests.rs
+++ b/zjit/src/hir/tests.rs
@@ -2712,9 +2712,9 @@ pub mod hir_build_tests {
           EntryPoint JIT(0)
           Jump bb2(v4)
         bb2(v6:BasicObject):
-          v11:Class = InvokeBuiltin leaf _bi20, v6
+          v11:HeapObject = InvokeBuiltin leaf _bi20, v6
           Jump bb3(v6, v11)
-        bb3(v13:BasicObject, v14:Class):
+        bb3(v13:BasicObject, v14:HeapObject):
           CheckInterrupts
           Return v14
         ");