Issue created by stacks.

This stack U3KXYA was reported by telemetry:

• compile/bug
• cmd/compile/internal/base.FatalfAt:+3
• cmd/compile/internal/base.Fatalf:=195
• cmd/compile/internal/gc.handlePanic:+7
• runtime.gopanic:+50
• runtime.goPanicIndex:+2
• cmd/compile/internal/types.IsExported:+1
• cmd/compile/internal/types.(*Sym).Less:+14
• cmd/compile/internal/types.expandiface.func2:+14
• sort.insertionSort_func:+2
• sort.stable_func:+8
• sort.SliceStable:+3
• cmd/compile/internal/types.expandiface:+18
• cmd/compile/internal/types.CalcSize:+120
• cmd/compile/internal/types.calcStructOffset:+2
• cmd/compile/internal/types.CalcStructSize:+13
• cmd/compile/internal/types.CalcSize:+245

cmd/compile@go1.23.2 go1.23.2 linux/amd64  (1)