As I understand it, the default importer used by go/types looks in the
intermediate Go object files, which don't have position information,
instead of in the source code. This doesn't appear to be made very
clear in the stdlib doc comments, but is mentioned by the types
tutorial at https://golang.org/s/types-tutorial#imports That tutorial
document also says:
"The golang.org/tools/x/go/loader package provides an alternative
Importer that addresses some of these problems. It loads a complete
program from source, performing cgo preprocessing if necessary,
followed by parsing and type-checking."
As far as I can see, that's not quite right, as that package doesn't
seem to define an importer as such, but if you use it, it has an
importer internally that reads from source, so I'd suggest using it
rather than go/types directly.
I've CC'd Alan Donovan, who can probably expand further on the design
choices made here.
cheers,
rog.
On 27 October 2017 at 01:51, <kpr...@atlassian.com> wrote:
> I have a simple example file:
> ==============================
>
> package gobbledy_gook
>
> import (
> "log"
> turtle "github.com/rs/zerolog/log"
> "os"
> "github.com/rs/zerolog"
> )
>
> var LOG = turtle.Logger.Output(os.Stdout).Error()
>
> func g() []zerolog.Logger {
> return []zerolog.Logger{}
> }
>
> func DoThings() {
> log.Println("proof of concept")
> g()[3].Error()
> return
> }
>
> ==============================
>
> I want to use go/ast & go/types to correctly identify the source code
> position of the turtle.Logger declaration (.../zerolog/log.go:13:5).
>
> If I parse only the gobbledy_gook package then the position ends up being
> <first file in FileSet>:1:9
> If I parse gobbledy_gook & zerolog packages and put them in the fset / list
> of files I get an unexpected package error
>
> Most of the below code is taken from the go/types#Info example code
>
> func main() {
> files := make([]*ast.File, 0, 8)
> fset := token.NewFileSet()
>
> for _, dir := range []string{
> "../../test_package",
> "go/src/github.com/rs/zerolog",
> "go/src/github.com/rs/zerolog/log",
> } {
> packages, err := parser.ParseDir(fset, dir, nil, parser.AllErrors)
> if err != nil {
> fmt.Println(err)
> return
> }
>
> for _, p := range packages {
> for _, file := range p.Files {
> files = append(files, file)
> }
> }
> }
> fmt.Println("Parse complete")
>
> info := types.Info{
> Types: make(map[ast.Expr]types.TypeAndValue),
> Defs: make(map[*ast.Ident]types.Object),
> Uses: make(map[*ast.Ident]types.Object),
> }
> var conf types.Config = types.Config{Importer: importer.Default()}
> pkg, err := conf.Check("fib", fset, files, &info)
> if err != nil {
> log.Println(err.Error())
> }
> fmt.Println("Check complete")
>
> // Print package-level variables in initialization order.
> fmt.Printf("InitOrder: %v\n\n", info.InitOrder)
>
> // For each named object, print the line and
> // column of its definition and each of its uses.
> fmt.Println("Defs and Uses of each named object:")
> usesByObj := make(map[types.Object][]string)
> for id, obj := range info.Uses {
> posn := fset.Position(id.Pos())
> lineCol := fmt.Sprintf("%d:%d", posn.Line, posn.Column)
> usesByObj[obj] = append(usesByObj[obj], lineCol)
> }
> var items []string
> for obj, uses := range usesByObj {
> sort.Strings(uses)
> item := fmt.Sprintf("%s:\n defined at %s\n used at %s",
> types.ObjectString(obj, types.RelativeTo(pkg)),
> fset.Position(obj.Pos()),
> strings.Join(uses, ", "))
> items = append(items, item)
> }
> sort.Strings(items) // sort by line:col, in effect
> fmt.Println(strings.Join(items, "\n"))
> fmt.Println()
>
> fmt.Println("Types and Values of each expression:")
> items = nil
> for expr, tv := range info.Types {
> var buf bytes.Buffer
> posn := fset.Position(expr.Pos())
> tvstr := tv.Type.String()
> if tv.Value != nil {
> tvstr += " = " + tv.Value.String()
> }
> // line:col | expr | mode : type = value
> fmt.Fprintf(&buf, "%s:%2d:%2d | %-19s | %s", posn.Filename,
> posn.Line, posn.Column, types.ExprString(expr), tvstr)
> items = append(items, buf.String())
> }
> sort.Strings(items)
> fmt.Println(strings.Join(items, "\n"))
> }
>
> --
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