You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: typexpr.go
    path of file: ./repos/fo/types
    
    the code of the file until where you have to start completion: // Copyright 2013 The Go Authors. All rights reserved.
// Modified work copyright 2018 Alex Browne. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// This file implements type-checking of identifiers and type expressions.

package types

import (
	"sort"
	"strconv"

	"github.com/albrow/fo/ast"
	"github.com/albrow/fo/constant"
	"github.com/albrow/fo/token"
)

// ident type-checks identifier e and initializes x with the value or type of e.
// If an error occurred, x.mode is set to invalid.
// For the meaning of def and path, see check.typ, below.
//
func (check *Checker) ident(x *operand, e *ast.Ident, def *Named, path []*TypeName) {
	x.mode = invalid
	x.expr = e

	scope, obj := check.scope.LookupParent(e.Name, check.pos)
	if obj == nil {
		if e.Name == "_" {
			check.errorf(e.Pos(), "cannot use _ as value or type")
		} else {
			check.errorf(e.Pos(), "undeclared name: %s", e.Name)
		}
		return
	}
	check.recordUse(e, obj)

	check.objDecl(obj, def, path)
	typ := obj.Type()
	assert(typ != nil)

	// The object may be dot-imported: If so, remove its package from
	// the map of unused dot imports for the respective file scope.
	// (This code is only needed for dot-imports. Without them,
	// we only have to mark variables, see *Var case below).
	if pkg := obj.Pkg(); pkg != check.pkg && pkg != nil {
		delete(check.unusedDotImports[scope], pkg)
	}

    
func (check *Checker) methodReceiver(scope *Scope, list *ast.FieldList) *Var {
	if list == nil {
		return nil
	}

	var recv *ast.Field
	switch len(list.List) {
	case 0:
		check.error(list.Pos(), "method is missing receiver")
		return NewParam(0, nil, "", Typ[Invalid]) // ignore recv below
	default:
		// more than one receiver
		check.error(list.List[len(list.List)-1].Pos(), "method must have exactly one receiver")
		fallthrough // continue with first receiver
	case 1:
		recv = list.List[0]
	}

	ftype := recv.Type
	isStar := false
	switch t := ftype.(type) {
	case *ast.Ellipsis:
		ftype = t.Elt
		check.invalidAST(recv.Pos(), "... not permitted")
		// ignore ... and continue
	case *ast.StarExpr:
		// Special case for StarExpr in receivers. It is okay for the type args to
		// be omitted.
		isStar = true
		ftype = t.X
	}
	typ := check.typ(ftype)
	if isStar {
		// convert back to a pointer receiver type.
		ptrType := new(Pointer)
		ptrType.base = typ
		typ = ptrType
	}

	var recvVar *Var
	switch len(recv.Names) {
	case 0:
		recvVar = NewParam(recv.Type.Pos(), check.pkg, "", typ)
		check.recordImplicit(recv, recvVar)
	default:
		// more than one name
		check.invalidAST(recv.Names[len(recv.Names)-1].Pos(), "method must have exactly one receiver")
		fallthrough // continue with first receiver
	case 1:
		name := recv.Names[0]
		if name.Name == "" {
			check.invalidAST(name.Pos(), "anonymous parameter")
			// ok to continue
		}
		recvVar = NewParam(name.Pos(), check.pkg, name.Name, typ)
		check.declare(scope, name, recvVar, scope.pos)
	}

	return recvVar
}