if hasRType(n, n.RType, "RType") {
		return n.RType
	}
	return mapRType(pos, n.Args[0].Type())
}

// IndexMapRType asserts that n is a map index operation, and returns
// an expression that yields the *runtime._type value representing the
// map type.
func IndexMapRType(pos src.XPos, n *ir.IndexExpr) ir.Node {
	assertOp(n, ir.OINDEXMAP)
	if hasRType(n, n.RType, "RType") {
		return n.RType
	}

		fn := mapfn(mapaccess2[fast], t, false)
		call = mkcall1(fn, fn.Type().ResultsTuple(), init, reflectdata.IndexMapRType(base.Pos, r), r.X, key)
	} else {
		fn := mapfn("mapaccess2_fat", t, true)
		z := reflectdata.ZeroAddr(w)
		call = mkcall1(fn, fn.Type().ResultsTuple(), init, reflectdata.IndexMapRType(base.Pos, r), r.X, key, z)
	}

	// mapaccess2* returns a typed bool, but due to spec changes,

	n.X = walkExpr(n.X, init)
	n.Index = walkExpr(n.Index, init)
	map_ := n.X
	t := map_.Type()
	fast := mapfast(t)
	key := mapKeyArg(fast, n, n.Index, n.Assigned)
	args := []ir.Node{reflectdata.IndexMapRType(base.Pos, n), map_, key}

	var mapFn ir.Node
	switch {
	case n.Assigned:
		mapFn = mapfn(mapassign[fast], t, false)
	case t.Elem().Size() > abi.ZeroValSize: