classmethod-on-type fold: require an exact classmethod

pyre/bench/synth/wrapper_subclass_get_override.cranelift.jitstats

@@ -0,0 +1,15 @@
+bridges_compiled=0
+descr_set_absent=0
+descr_set_ambiguous=0
+descr_set_stale_absent=0
+fbw_blackhole_adopted_multi_frame=0
+fbw_blackhole_adopted_single_frame=0
+fbw_rolled_back_with_effects=0
+fbw_store_journal_rollback_failed=0
+field_pos_attached_misplaced=0
+field_pos_spec_misplaced=0
+guard_failures=6
+internal_compile_panics=0
+loops_aborted=0
+loops_compiled=6
+retraces_compiled=0

pyre/bench/synth/wrapper_subclass_get_override.dynasm.jitstats

@@ -0,0 +1,15 @@
+bridges_compiled=0
+descr_set_absent=0
+descr_set_ambiguous=0
+descr_set_stale_absent=0
+fbw_blackhole_adopted_multi_frame=0
+fbw_blackhole_adopted_single_frame=0
+fbw_rolled_back_with_effects=0
+fbw_store_journal_rollback_failed=0
+field_pos_attached_misplaced=0
+field_pos_spec_misplaced=0
+guard_failures=6
+internal_compile_panics=0
+loops_aborted=0
+loops_compiled=6
+retraces_compiled=0

pyre/bench/synth/wrapper_subclass_get_override.py

@@ -0,0 +1,115 @@
+# `typeobject.py descr_getattribute` resolves an attribute through
+# `type(descr).__get__`, so a `classmethod` / `staticmethod` SUBCLASS that
+# overrides `__get__` binds through that override.  A fold that unwraps
+# `w_function` in its place calls the wrapped callable directly and never
+# reaches the override, which is why every wrapper type test is exact.
+#
+# One loop per fold that unwraps a wrapper — class receiver, instance
+# receiver, and the `__getattr__` hook's two arms — each reading through a
+# direct call so the fold is the shape that records, not a lambda's
+# megamorphic call site.  Every loop must report the OVERRIDE.
+# Sized for the fold, not for throughput: the declining path runs the whole
+# descriptor protocol per iteration, so this costs far more per `N` than a
+# folded loop.  Every loop still compiles at N=2000, leaving a wide margin.
+N = 100000
+
+
+class GetOverridingClassMethod(classmethod):
+    def __get__(self, obj, cls=None):
+        return overridden
+
+
+class GetOverridingStaticMethod(staticmethod):
+    def __get__(self, obj, cls=None):
+        return overridden
+
+
+def overridden(*args):
+    return 'override'
+
+
+def wrapped_class(cls, x):
+    return 'wrapped'
+
+
+def wrapped_static(x):
+    return 'wrapped'
+
+
+class Attrs:
+    cm = GetOverridingClassMethod(wrapped_class)
+    sm = GetOverridingStaticMethod(wrapped_static)
+
+
+class ClassHook:
+    __getattr__ = GetOverridingClassMethod(wrapped_class)
+
+
+class StaticHook:
+    __getattr__ = GetOverridingStaticMethod(wrapped_static)
+
+
+def classmethod_on_type():
+    seen = None
+    i = 0
+    while i < N:
+        seen = Attrs.cm(i)
+        i += 1
+    print('classmethod on type', seen)
+
+
+def staticmethod_on_type():
+    seen = None
+    i = 0
+    while i < N:
+        seen = Attrs.sm(i)
+        i += 1
+    print('staticmethod on type', seen)
+
+
+def classmethod_on_instance():
+    obj = Attrs()
+    seen = None
+    i = 0
+    while i < N:
+        seen = obj.cm(i)
+        i += 1
+    print('classmethod on instance', seen)
+
+
+def staticmethod_on_instance():
+    obj = Attrs()
+    seen = None
+    i = 0
+    while i < N:
+        seen = obj.sm(i)
+        i += 1
+    print('staticmethod on instance', seen)
+
+
+def classmethod_getattr_hook():
+    obj = ClassHook()
+    seen = None
+    i = 0
+    while i < N:
+        seen = obj.missing
+        i += 1
+    print('classmethod getattr hook', seen)
+
+
+def staticmethod_getattr_hook():
+    obj = StaticHook()
+    seen = None
+    i = 0
+    while i < N:
+        seen = obj.missing
+        i += 1
+    print('staticmethod getattr hook', seen)
+
+
+classmethod_on_type()
+staticmethod_on_type()
+classmethod_on_instance()
+staticmethod_on_instance()
+classmethod_getattr_hook()
+staticmethod_getattr_hook()

pyre/bench/synth/wrapper_subclass_get_override.wasm.jitstats

@@ -0,0 +1,15 @@
+bridges_compiled=0
+descr_set_absent=0
+descr_set_ambiguous=0
+descr_set_stale_absent=0
+fbw_blackhole_adopted_multi_frame=0
+fbw_blackhole_adopted_single_frame=0
+fbw_rolled_back_with_effects=0
+fbw_store_journal_rollback_failed=0
+field_pos_attached_misplaced=0
+field_pos_spec_misplaced=0
+guard_failures=6
+internal_compile_panics=0
+loops_aborted=0
+loops_compiled=6
+retraces_compiled=0

pyre/pyre-interpreter/src/baseobjspace.rs

@@ -9890,7 +9890,7 @@ pub unsafe fn load_method_fast_path(
 /// follow `type.__getattribute__`).  A name the metatype defines as a DATA
 /// DESCRIPTOR is declined too, since that is the one entry `descr_getattribute`
 /// selects ahead of the class's own MRO.  An uncacheable type and any
-/// non-`classmethod` descriptor also decline.
+/// descriptor that is not an EXACT `classmethod` also decline.
 ///
 /// # Safety
 /// `w_obj` must be a valid object pointer (null tolerated).
@@ -9925,7 +9925,10 @@ pub unsafe fn classmethod_on_type_fast_path(
         return None;
     }
     let w_descr = lookup_in_type(w_type, name)?;
-    if !pyre_object::is_classmethod(w_descr) {
+    // EXACT, for the reason the `__getattr__`-hook arm records: a `classmethod`
+    // subclass overriding `__get__` binds through that override, so unwrapping
+    // `w_function` in its place calls the wrong callable.
+    if !unsafe { pyre_object::function::is_exact_classmethod(w_descr) } {
         return None;
     }
     let w_func = pyre_object::function::w_classmethod_get_func(w_descr);