[ty] Benchmarks for problematic implicit instance attributes cases (#20133)

## Summary

Add regression benchmarks for the problematic cases in
https://github.com/astral-sh/ty/issues/758. I'd like to merge this
before https://github.com/astral-sh/ruff/pull/20128 to measure the
impact (local tests show that this will "solve" both cases).

crates/ruff_benchmark/benches/ty.rs

@@ -450,9 +450,6 @@ fn benchmark_complex_constrained_attributes_2(criterion: &mut Criterion) {
                     r#"
                     class C:
                         def f(self: "C"):
-                            self.a = ""
-                            self.b = ""
-
                             if isinstance(self.a, str):
                                 return
 
@@ -466,6 +463,56 @@ fn benchmark_complex_constrained_attributes_2(criterion: &mut Criterion) {
                                 return
                             if isinstance(self.b, str):
                                 return
+                            if isinstance(self.b, str):
+                                return
+                            if isinstance(self.b, str):
+                                return
+
+                            self.a = ""
+                            self.b = ""
+                    "#,
+                )
+            },
+            |case| {
+                let Case { db, .. } = case;
+                let result = db.check();
+                assert_eq!(result.len(), 0);
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
+fn benchmark_complex_constrained_attributes_3(criterion: &mut Criterion) {
+    setup_rayon();
+
+    criterion.bench_function("ty_micro[complex_constrained_attributes_3]", |b| {
+        b.iter_batched_ref(
+            || {
+                // This is a regression test for https://github.com/astral-sh/ty/issues/758
+                setup_micro_case(
+                    r#"
+                    class GridOut:
+                        def __init__(self: "GridOut") -> None:
+                            self._buffer = b""
+
+                        def _read_size_or_line(self: "GridOut", size: int = -1):
+                            if size > self._position:
+                                size = self._position
+                                pass
+                            if size == 0:
+                                return bytes()
+
+                            while size > 0:
+                                if self._buffer:
+                                    buf = self._buffer
+                                    self._buffer = b""
+                                else:
+                                    buf = b""
+
+                                if len(buf) > size:
+                                    self._buffer = buf
+                                    self._position -= len(self._buffer)
                     "#,
                 )
             },
@@ -668,6 +715,7 @@ criterion_group!(
     benchmark_tuple_implicit_instance_attributes,
     benchmark_complex_constrained_attributes_1,
     benchmark_complex_constrained_attributes_2,
+    benchmark_complex_constrained_attributes_3,
     benchmark_many_enum_members,
 );
 criterion_group!(project, anyio, attrs, hydra, datetype);