}
	if mapfast(t) == mapslow || isfat {
		return typecheck.LookupRuntime(name, t.Key(), t.Elem(), t.Key(), t.Elem())
	}
	return typecheck.LookupRuntime(name, t.Key(), t.Elem(), t.Elem())
}

func mapfndel(name string, t *types.Type) ir.Node {
	if !t.IsMap() {
		base.Fatalf("mapfn %v", t)
	}
	if mapfast(t) == mapslow {
		return typecheck.LookupRuntime(name, t.Key(), t.Elem(), t.Key())
	}

	map_ := n.Args[0]
	key := n.Args[1]
	map_ = walkExpr(map_, init)
	key = walkExpr(key, init)

	t := map_.Type()
	fast := mapfast(t)
	key = mapKeyArg(fast, n, key, false)
	return mkcall1(mapfndel(mapdelete[fast], t), nil, init, reflectdata.DeleteMapRType(base.Pos, n), map_, key)
}

// walkLenCap walks an OLEN or OCAP node.
func walkLenCap(n *ir.UnaryExpr, init *ir.Nodes) ir.Node {
	if isRuneCount(n) {

//
// variable   <expr> (<untyped kind> <mode>                    )
// variable   <expr> (               <mode>       of type <typ>)
//
// mapindex   <expr> (<untyped kind> <mode>                    )
// mapindex   <expr> (               <mode>       of type <typ>)
//
// value      <expr> (<untyped kind> <mode>                    )
// value      <expr> (               <mode>       of type <typ>)
//

//
// variable   <expr> (<untyped kind> <mode>                    )
// variable   <expr> (               <mode>       of type <typ>)
//
// mapindex   <expr> (<untyped kind> <mode>                    )
// mapindex   <expr> (               <mode>       of type <typ>)
//
// value      <expr> (<untyped kind> <mode>                    )
// value      <expr> (               <mode>       of type <typ>)
//

func (tv TypeAndValue) Assignable() bool {
	return tv.mode == variable || tv.mode == mapindex
}

// HasOk reports whether the corresponding expression may be
// used on the rhs of a comma-ok assignment.
func (tv TypeAndValue) HasOk() bool {
	return tv.mode == commaok || tv.mode == mapindex
}

// Instance reports the type arguments and instantiated type for type and

	}

	for _, tt := range tests {
		b.Run(tt.label, func(b *testing.B) {
			b.Run("MapIndex", func(b *testing.B) {
				b.ReportAllocs()
				for i := 0; i < b.N; i++ {
					for j := tt.keys.Len() - 1; j >= 0; j-- {
						tt.m.MapIndex(tt.keys.Index(j))
					}
				}
			})
			b.Run("SetMapIndex", func(b *testing.B) {
				b.ReportAllocs()
				for i := 0; i < b.N; i++ {

func (tv TypeAndValue) Assignable() bool {
	return tv.mode == variable || tv.mode == mapindex
}

// HasOk reports whether the corresponding expression may be
// used on the rhs of a comma-ok assignment.
func (tv TypeAndValue) HasOk() bool {
	return tv.mode == commaok || tv.mode == mapindex
}

// Instance reports the type arguments and instantiated type for type and

			return false
		}
		var key operand
		check.expr(nil, &key, index)
		check.assignment(&key, typ.key, "map index")
		// ok to continue even if indexing failed - map element type is known
		x.mode = mapindex
		x.typ = typ.elem
		x.expr = e.Orig
		return false

	case *Interface:
		if !isTypeParam(x.typ) {
			break
		}
		// TODO(gri) report detailed failure cause for better error messages

	switch x.mode {
	case invalid:
		return Typ[Invalid]
	case variable, mapindex:
		// ok
	default:
		if sel, ok := x.expr.(*ast.SelectorExpr); ok {
			var op operand
			check.expr(nil, &op, sel.X)
			if op.mode == mapindex {
				check.errorf(&x, UnaddressableFieldAssign, "cannot assign to struct field %s in map", ExprString(x.expr))
				return Typ[Invalid]
			}

	switch x.mode {
	case invalid:
		return Typ[Invalid]
	case variable, mapindex:
		// ok
	default:
		if sel, ok := x.expr.(*syntax.SelectorExpr); ok {
			var op operand
			check.expr(nil, &op, sel.X)
			if op.mode == mapindex {
				check.errorf(&x, UnaddressableFieldAssign, "cannot assign to struct field %s in map", ExprString(x.expr))
				return Typ[Invalid]
			}