// Type checking guarantees that TIDEAL len/cap are positive and fit in an int.
	// The case of len or cap overflow when converting TUINT or TUINTPTR to TINT
	// will be handled by the negative range checks in unsafeslice during runtime.
	if ir.ShouldCheckPtr(ir.CurFunc, 1) {
		fnname := "unsafeslicecheckptr"
		fn := typecheck.LookupRuntime(fnname)

		n.SetType(nil)
		return n
	}
	if !n.Y.Type().IsInteger() {
		n.SetType(nil)
		return n
	}
	n.SetType(n.X.Type())
	return n
}

// tcUnsafeSlice typechecks an OUNSAFESLICE node.
func tcUnsafeSlice(n *ir.BinaryExpr) *ir.BinaryExpr {
	n.X = Expr(n.X)
	n.Y = Expr(n.Y)
	if n.X.Type() == nil || n.Y.Type() == nil {
		n.SetType(nil)
		return n
	}
	t := n.X.Type()

	ORETURN:           "return",
	ORSH:              ">>",
	OSELECT:           "select",
	OSEND:             "<-",
	OSUB:              "-",
	OSWITCH:           "switch",
	OUNSAFEADD:        "unsafe.Add",
	OUNSAFESLICE:      "unsafe.Slice",
	OUNSAFESLICEDATA:  "unsafe.SliceData",
	OUNSAFESTRING:     "unsafe.String",
	OUNSAFESTRINGDATA: "unsafe.StringData",
	OXOR:              "^",
}

			base.FatalfAt(n.Pos(), "mayCall %+v", n)
		}

		switch n.Op() {
		default:
			base.FatalfAt(n.Pos(), "mayCall %+v", n)

		case ir.OCALLFUNC, ir.OCALLINTER,
			ir.OUNSAFEADD, ir.OUNSAFESLICE:
			return true

		case ir.OINDEX, ir.OSLICE, ir.OSLICEARR, ir.OSLICE3, ir.OSLICE3ARR, ir.OSLICESTR,
			ir.ODEREF, ir.ODOTPTR, ir.ODOTTYPE, ir.ODYNAMICDOTTYPE, ir.ODIV, ir.OMOD,
			ir.OSLICE2ARR, ir.OSLICE2ARRPTR:

		ir.OLEN,
		ir.OMAKE,
		ir.OMAX,
		ir.OMIN,
		ir.ONEW,
		ir.OPANIC,
		ir.OPRINT,
		ir.OPRINTLN,
		ir.OREAL,
		ir.ORECOVER,
		ir.ORECOVERFP,
		ir.ORECV,
		ir.OUNSAFEADD,
		ir.OUNSAFESLICE,
		ir.OUNSAFESLICEDATA,
		ir.OUNSAFESTRING,
		ir.OUNSAFESTRINGDATA:
		return true
	}
	return false

	case ir.ORECOVER:
		n := n.(*ir.CallExpr)
		return tcRecover(n)

	case ir.OUNSAFEADD:
		n := n.(*ir.BinaryExpr)
		return tcUnsafeAdd(n)

	case ir.OUNSAFESLICE:
		n := n.(*ir.BinaryExpr)
		return tcUnsafeSlice(n)

	case ir.OUNSAFESLICEDATA:
		n := n.(*ir.UnaryExpr)
		return tcUnsafeData(n)

	case ir.OUNSAFESTRING:
		n := n.(*ir.BinaryExpr)
		return tcUnsafeString(n)

		ir.OUNSAFEADD:
		n := n.(*ir.BinaryExpr)
		n.X = walkExpr(n.X, init)
		n.Y = walkExpr(n.Y, init)
		return n

	case ir.OUNSAFESLICE:
		n := n.(*ir.BinaryExpr)
		return walkUnsafeSlice(n, init)

	case ir.OUNSAFESTRING:
		n := n.(*ir.BinaryExpr)
		return walkUnsafeString(n, init)

	case ir.OUNSAFESTRINGDATA, ir.OUNSAFESLICEDATA: