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afe6bebde7
## Summary
- Fix false positive cycle detection in `gutil.Dump`
- Change from global pointer tracking to path-based cycle detection
- Shared references (multiple fields pointing to same object) no longer
incorrectly marked as cycles
## Problem
When using `gutil.Dump` with structs containing fields that share the
same `reflect.Type` (e.g., multiple `int` fields), the second field's
type was incorrectly displayed as `<cycle dump 0x...>`.
Example from issue:
```go
type User struct {
Id int `params:"id"`
Name int `params:"name"`
}
fields, _ := gstructs.TagFields(&user, []string{"p", "params"})
gutil.Dump(fields) // Second field's Type shows "<cycle dump>" instead of "int"
```
## Solution
Change cycle detection from global to path-based:
- Add `defer delete()` to remove pointer from tracking set when function
returns
- Only detect true cycles (A→B→A), not shared references (A,B both point
to C)
## Benchmark Comparison
Run benchmark with:
```bash
cd util/gutil && go test -bench=Benchmark_Dump -benchmem -run=^$
```
**Before fix (master branch):**
| Benchmark | ns/op | B/op | allocs/op |
|-----------|-------|------|-----------|
| Shallow | 4071 | 5989 | 85 |
| Nested20 | 105700 | 173993 | 1952 |
| Deep50 | 422515 | 692298 | 4869 |
**After fix (this PR):**
| Benchmark | ns/op | B/op | allocs/op |
|-----------|-------|------|-----------|
| Shallow | 4049 | 5989 | 85 |
| Nested20 | 103065 | 173990 | 1952 |
| Deep50 | 469502 | 692291 | 4869 |
**Performance impact**:
- Memory allocation (B/op and allocs/op) is **identical**
- Execution time is within normal variance (±5-10%)
- The `defer delete()` operation is O(1), negligible compared to
reflection overhead
## Test plan
- [x] All existing `gutil` tests pass (68 tests)
- [x] Added `Test_Dump_Issue2902_SharedPointer` - shared pointer not
marked as cycle
- [x] Added `Test_Dump_Issue2902_SameTypeFields` - original issue
scenario
- [x] Added benchmark tests for performance tracking
- [x] Verified real cycles still detected correctly
Fixes #2902