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

			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

// type parameter. Otherwise the result is nil. Errors are reported through the err parameter.
// Note: infer may fail (return nil) due to invalid args operands without reporting additional errors.
func (check *Checker) infer(posn positioner, tparams []*TypeParam, targs []Type, params *Tuple, args []*operand, reverse bool, err *error_) (inferred []Type) {
	// Don't verify result conditions if there's no error handler installed:

	var x operand
	if init != nil {
		if inherited {
			// The initialization expression is inherited from a previous
			// constant declaration, and (error) positions refer to that
			// expression and not the current constant declaration. Use
			// the constant identifier position for any errors during
			// init expression evaluation since that is all we have
			// (see issues go.dev/issue/42991, go.dev/issue/42992).

func (s *FileSet) PositionFor(p Pos, adjusted bool) (pos Position) {
	if p != NoPos {
		if f := s.file(p); f != nil {
			return f.position(p, adjusted)
		}
	}
	return
}

// Position converts a [Pos] p in the fileset into a Position value.
// Calling s.Position(p) is equivalent to calling s.PositionFor(p, true).
func (s *FileSet) Position(p Pos) (pos Position) {
	return s.PositionFor(p, true)
}

//
// The position base is used to determine the "relative" position, that is the
// filename and line number relative to the position base. If the base refers
// to the current file, there is no difference between absolute and relative
// positions. If it refers to a //line directive, a relative position is relative
// to that directive. A position base in turn contains the position at which it
// was introduced in the current file.
type Pos struct {

	f.SetLinesForContent(src)

	// verify position info
	for i, offs := range f.lines {
		got1 := f.PositionFor(f.Pos(offs), false)
		got2 := f.PositionFor(f.Pos(offs), true)
		got3 := f.Position(f.Pos(offs))
		want := Position{filename, offs, i + 1, 1}
		checkPos(t, "1. PositionFor unadjusted", got1, want)
		checkPos(t, "1. PositionFor adjusted", got2, want)
		checkPos(t, "1. Position", got3, want)
	}