invalidOp  = "invalid operation: "
)

// The positioner interface is used to extract the position of type-checker errors.
type positioner interface {
	Pos() token.Pos
}

func (check *Checker) error(at positioner, code Code, msg string) {
	err := check.newError(code)
	err.addf(at, "%s", msg)
	err.report()
}

func (check *Checker) errorf(at positioner, code Code, format string, args ...any) {

// dddErrPos returns the positioner for reporting an invalid ... use in a call.
func dddErrPos(call *ast.CallExpr) positioner { return atPos(call.Ellipsis) }

// argErrPos returns positioner for reporting an invalid argument count.
func argErrPos(call *ast.CallExpr) positioner { return inNode(call, call.Rparen) }

// startPos returns the start position of node n.
func startPos(n ast.Node) token.Pos { return n.Pos() }

//   - github.com/goplus/gox
//
// Do not remove or change the type signature.
// See go.dev/issue/67401.
//
//go:linkname badlinkname_Checker_infer go/types.(*Checker).infer

)

// allowVersion reports whether the current package at the given position
// is allowed to use version v. If the position is unknown, the specified
// module version (Config.GoVersion) is used. If that version is invalid,
// allowVersion returns true.
func (check *Checker) allowVersion(at positioner, v goVersion) bool {
	fileVersion := check.conf.GoVersion
	if pos := at.Pos(); pos.IsValid() {

		case *ast.FuncDecl:
			if n.Name.Name == "infer" {
				// rewrite (pos token.Pos, ...) to (posn positioner, ...)
				par := n.Type.Params.List[0]
				if len(par.Names) == 1 && par.Names[0].Name == "pos" {
					par.Names[0] = newIdent(par.Names[0].Pos(), "posn")
					par.Type = newIdent(par.Type.Pos(), "positioner")
					return true
				}
			}
		case *ast.CallExpr:

	pos           token.Pos              // if valid, identifiers are looked up as if at position pos (used by Eval)
	iota          constant.Value         // value of iota in a constant declaration; nil otherwise
	errpos        positioner             // if set, identifier position of a constant with inherited initializer
	inTParamList  bool                   // set if inside a type parameter list

			}
			continue // ignore
		}

		// The go/parser doesn't accept method type parameters but an ast.FuncType may have them.
		if sig.tparams != nil {
			var at positioner = f.Type
			if ftyp, _ := f.Type.(*ast.FuncType); ftyp != nil && ftyp.TypeParams != nil {
				at = ftyp.TypeParams
			}
			check.error(at, InvalidSyntaxTree, "methods cannot have type parameters")
		}

			return
		}
	}
	check.errorf(rhs0, WrongAssignCount, "assignment mismatch: %s but %s", vars, vals)
}

func (check *Checker) returnError(at positioner, lhs []*Var, rhs []*operand) {
	l, r := len(lhs), len(rhs)
	qualifier := "not enough"
	if r > l {
		at = rhs[l] // report at first extra value
		qualifier = "too many"
	} else if r > 0 {

// and x.mode is set to invalid.
func (check *Checker) funcInst(T *target, pos token.Pos, x *operand, ix *typeparams.IndexExpr, infer bool) ([]Type, []ast.Expr) {
	assert(T != nil || ix != nil)

	var instErrPos positioner
	if ix != nil {
		instErrPos = inNode(ix.Orig, ix.Lbrack)
		x.expr = ix.Orig // if we don't have an index expression, keep the existing expression of x
	} else {
		instErrPos = atPos(pos)
	}

	file := check.files[fileNo]
	if pos := file.Pos(); pos.IsValid() {
		return check.fset.File(pos).Name()
	}
	return fmt.Sprintf("file[%d]", fileNo)
}

func (check *Checker) importPackage(at positioner, path, dir string) *Package {
	// If we already have a package for the given (path, dir)
	// pair, use it instead of doing a full import.
	// Checker.impMap only caches packages that are marked Complete