final := T
		// - For conversions to interfaces, except for untyped nil arguments
		//   and isTypes2, use the argument's default type.
		// - For conversions of untyped constants to non-constant types, also
		//   use the default type (e.g., []byte("foo") should report string
		//   not []byte as type for the constant "foo").
		// - If !isTypes2, keep untyped nil for untyped nil arguments.

		final := T
		// - For conversions to interfaces, except for untyped nil arguments
		//   and isTypes2, use the argument's default type.
		// - For conversions of untyped constants to non-constant types, also
		//   use the default type (e.g., []byte("foo") should report string
		//   not []byte as type for the constant "foo").
		// - If !isTypes2, keep untyped nil for untyped nil arguments.

// different between go/types and types2. Factoring
// out this code allows more of the rest of the code
// to be shared.

package types

import (
	"go/ast"
	"go/constant"
	"go/token"
)

const isTypes2 = false

// cmpPos compares the positions p and q and returns a result r as follows:
//
// r <  0: p is before q
// r == 0: p and q are the same position (but may not be identical)
// r >  0: p is after q
//

// out this code allows more of the rest of the code
// to be shared.

package types2

import (
	"cmd/compile/internal/syntax"
	"go/constant"
	"go/token"
)

const isTypes2 = true

// cmpPos compares the positions p and q and returns a result r as follows:
//
// r <  0: p is before q
// r == 0: p and q are the same position (but may not be identical)
// r >  0: p is after q
//

//
// cgofunc    <expr> (<untyped kind> <mode>                    )
// cgofunc    <expr> (               <mode>       of type <typ>)
func operandString(x *operand, qf Qualifier) string {
	// special-case nil
	if isTypes2 {
		if x.mode == nilvalue {
			switch x.typ {
			case nil, Typ[Invalid]:
				return "nil (with invalid type)"
			case Typ[UntypedNil]:
				return "nil"
			default:

//
// cgofunc    <expr> (<untyped kind> <mode>                    )
// cgofunc    <expr> (               <mode>       of type <typ>)
func operandString(x *operand, qf Qualifier) string {
	// special-case nil
	if isTypes2 {
		if x.mode == nilvalue {
			switch x.typ {
			case nil, Typ[Invalid]:
				return "nil (with invalid type)"
			case Typ[UntypedNil]:
				return "nil"
			default:

	}

	// In go/types, if there is a sub-error with a valid position,
	// call the typechecker error handler for each sub-error.
	// Otherwise, call it once, with a single combined message.
	multiError := false
	if !isTypes2 {
		for i := 1; i < len(err.desc); i++ {
			if err.desc[i].pos.IsKnown() {
				multiError = true
				break
			}
		}
	}

	if multiError {
		for i := range err.desc {
			p := &err.desc[i]

func (check *Checker) assignment(x *operand, T Type, context string) {
	check.singleValue(x)

	switch x.mode {
	case invalid:
		return // error reported before
	case nilvalue:
		assert(isTypes2)
		// ok
	case constant_, variable, mapindex, value, commaok, commaerr:
		// ok
	default:
		// we may get here because of other problems (go.dev/issue/39634, crash 12)

func (check *Checker) assignment(x *operand, T Type, context string) {
	check.singleValue(x)

	switch x.mode {
	case invalid:
		return // error reported before
	case nilvalue:
		assert(isTypes2)
		// ok
	case constant_, variable, mapindex, value, commaok, commaerr:
		// ok
	default:
		// we may get here because of other problems (go.dev/issue/39634, crash 12)

	}

	// In go/types, if there is a sub-error with a valid position,
	// call the typechecker error handler for each sub-error.
	// Otherwise, call it once, with a single combined message.
	multiError := false
	if !isTypes2 {
		for i := 1; i < len(err.desc); i++ {
			if err.desc[i].posn.Pos().IsValid() {
				multiError = true
				break
			}
		}
	}

	if multiError {
		for i := range err.desc {