if !ok {
		return ""
	}
	return pkg.why()
}

// WhyDepth returns the number of steps in the Why listing.
// If there is no reason for the package to be in the current build,
// WhyDepth returns 0.
func WhyDepth(path string) int {
	n := 0
	pkg, _ := loaded.pkgCache.Get(path)
	for p := pkg; p != nil; p = p.stack {
		n++
	}
	return n

	var err error
	_, file, err := modfetch.InfoFile(ctx, m.Path, m.Version)
	if err != nil {
		return err
	}
	m.Info = file
	m.GoMod, err = modfetch.GoModFile(ctx, m.Path, m.Version)
	if err != nil {
		return err
	}
	m.GoModSum, err = modfetch.GoModSum(ctx, m.Path, m.Version)
	if err != nil {
		return err
	}
	mod := module.Version{Path: m.Path, Version: m.Version}

		case ir.OADDSTR:
			return addStr(x.(*ir.AddStringExpr))
		}
		return x
	}
	n = edit(n)
	return n, valid
}

// truncate returns the result of force converting c to type t,
// truncating its value as needed, like a conversion of a variable.
// If the conversion is too difficult, truncate returns nil, false.
func truncate(c ir.Node, t *types.Type) (ir.Node, bool) {
	ct := c.Type()
	cv := c.Val()

			// (e.g., go.dev/issue/49005). Return an invalid type instead.
			if !isValid(typ.base) {
				return Typ[Invalid]
			}
			return typ
		}

		check.errorf(e0, NotAType, "%s is not a type", e0)
		check.use(e0)

	case *syntax.FuncType:
		typ := new(Signature)
		setDefType(def, typ)
		check.funcType(typ, nil, nil, e)
		return typ

	case *syntax.InterfaceType:

			return err
		}

		if !info.IsDir() {
			return nil
		}
		if !strings.HasPrefix(path, root) {
			panic(fmt.Errorf("path %v in walk doesn't have modroot %v as prefix", path, modroot))
		}
		rel := path[len(root):]
		packages = append(packages, importRaw(modroot, rel))
		return nil
	})
	if err != nil {
		return nil, err
	}
	return encodeModuleBytes(packages), nil
}

			return true
		}

	case *syntax.BlockStmt:
		return check.isTerminatingList(s.List, "")

	case *syntax.IfStmt:
		if s.Else != nil &&
			check.isTerminating(s.Then, "") &&
			check.isTerminating(s.Else, "") {
			return true
		}

	case *syntax.SwitchStmt:
		return check.isTerminatingSwitch(s.Body, label)

	case *syntax.SelectStmt:
		for _, cc := range s.Body {

		case sc.IsString():
			return "convTstring", types.Types[types.TSTRING], false
		case sc.IsSlice():
			return "convTslice", types.NewSlice(types.Types[types.TUINT8]), false // the element type doesn't matter
		}
	}

	if from.HasPointers() {
		return "convT", types.Types[types.TUNSAFEPTR], true
	}
	return "convTnoptr", types.Types[types.TUNSAFEPTR], true
}

	if isStandardImportPath(pkgpath) || !Enabled() || cfg.BuildMod == "vendor" {
		return ""
	}
	m, ok := findModule(loaded, pkgpath)
	if !ok {
		return ""
	}
	root, _, err := fetch(ctx, m)
	if err != nil {
		return ""
	}
	return root
}

func ModuleInfo(ctx context.Context, path string) *modinfo.ModulePublic {
	if !Enabled() {
		return nil
	}

	if path, vers, found := strings.Cut(path, "@"); found {

	return sw.sp[len(sw.sp)-1].endOffset() - sw.pos
}
func (sw sparseFileWriter) physicalRemaining() int64 {
	return sw.fw.physicalRemaining()
}

// zeroWriter may only be written with NULs, otherwise it returns errWriteHole.
type zeroWriter struct{}

func (zeroWriter) Write(b []byte) (int, error) {
	for i, c := range b {
		if c != 0 {
			return i, errWriteHole
		}
	}
	return len(b), nil
}

into

	{
		var #next int
		f(func(x T1) bool {
			...
			return true
		})
		... check #next ...
	}

The variable #next is an integer code that says what to do when f
returns. Each difficult statement sets #next and then returns false to
stop f.

A plain "return" rewrites to {#next = -1; return false}.
The return false breaks the loop. Then when f returns, the "check
#next" section includes

	if #next == -1 { return }