start with a fresh ScheduleItemContext in process_replay [pr] (#7236)

tinygrad/engine/schedule.py

@@ -1,6 +1,6 @@
 import sys, atexit, functools
 from collections import defaultdict, deque
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 from typing import Callable, Set, Tuple, List, Dict, Optional, DefaultDict, cast
 from tinygrad.ops import BUFFER_UOPS, UNSAFE_PAD_OPS, MetaOps, ReduceOps, UnaryOps, UOp, UOps, PatternMatcher, UPat, Variable, resolve, \
     graph_rewrite, track_rewrites, sint
@@ -132,8 +132,8 @@ view_right = merge_views+PatternMatcher([
 @dataclass(frozen=True)
 class ScheduleItemContext:
   var_vals: Dict[Variable, int]
-  sts: Set[ShapeTracker]
-  bufs: List[UOp]
+  sts: Set[ShapeTracker] = field(default_factory=set)
+  bufs: List[UOp] = field(default_factory=list)
 
 def _append_st_vars(ctx:ScheduleItemContext, x:UOp) -> Optional[UOp]:
   if (st:=unwrap(x.st)) in ctx.sts: return None
@@ -158,7 +158,7 @@ PROCESS_REPLAY_CAPTURE: List[Tuple[UOp, ScheduleItemContext, UOp]] = []
 def full_ast_rewrite(base_sink:UOp, ctx:ScheduleItemContext) -> UOp:
   sink = graph_rewrite(graph_rewrite(base_sink, view_left), view_right)
   ret = graph_rewrite(sink, to_si, ctx)
-  PROCESS_REPLAY_CAPTURE.append((base_sink, ctx, ret))
+  PROCESS_REPLAY_CAPTURE.append((base_sink, ScheduleItemContext(ctx.var_vals), ret))
   return ret
 
 if getenv("RUN_PROCESS_REPLAY"):
@@ -198,7 +198,7 @@ def _lower_lazybuffer(outs:List[LazyBuffer], buf_uops:Dict[Buffer, UOp], var_val
   metadata: Dict[UOp, Metadata] = {}
   sink = UOp(UOps.SINK, src=tuple(UOp.store(buf_uops[out.buffer], ShapeTracker.from_shape(out.shape).to_uop(),
                                             to_uop(out, outs, inputs, buf_uops, metadata, cache)) for out in outs))
-  sink = full_ast_rewrite(sink, ctx:=ScheduleItemContext(var_vals, set(), []))
+  sink = full_ast_rewrite(sink, ctx:=ScheduleItemContext(var_vals))
   # we also allow masked views. if it has a single view and it's equal when you shrink a contig, it's fine
   if len(assign_targets:=[x.src[0] for x in sink.sparents if x.op is UOps.ASSIGN]) != 0:
     if not all((s:=x.st_arg).contiguous or (len(s.views) == 1 and (m:=s.views[0].mask) is not None \