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arf/file/error.go

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package file
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import "os"
import "fmt"
type ErrorKind int
const (
ErrorKindError ErrorKind = iota
ErrorKindWarn
)
type Error struct {
Location
width int
message string
kind ErrorKind
}
// NewError creates a new error at the specified location.
func NewError (
location Location,
width int,
message string,
kind ErrorKind,
) (
err *Error,
) {
return &Error {
Location: location,
width: width,
message: message,
kind: kind,
}
}
// Error returns a formatted error message as a string.
func (err Error) Error () (formattedMessage string) {
switch err.kind {
case ErrorKindError:
formattedMessage += "ERR"
case ErrorKindWarn:
formattedMessage += "!!!"
}
// print information about the location of the mistake
if err.width > 0 {
formattedMessage += fmt.Sprint (
" ", err.Location.row + 1,
":", err.Location.column + 1)
}
formattedMessage += " in " + err.Location.file.path + "\n"
if err.width > 0 {
// print erroneous line
formattedMessage +=
err.Location.file.lines[err.Location.row] + "\n"
// print an arrow with a tail spanning the width of the mistake
columnCountdown := err.Location.column
for columnCountdown > 0 {
formattedMessage += " "
columnCountdown --
}
for err.width > 1 {
formattedMessage += "-"
}
formattedMessage += "-\n"
}
formattedMessage += err.message + "-\n"
return
}
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// Print formats the error and prints it to stderr.
func (err Error) Print () {
os.Stderr.Write([]byte(err.Error()))
}