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|
package parse
import (
"bytes"
"errors"
"fmt"
"io"
"strings"
"unicode/utf8"
"src.elv.sh/pkg/diag"
)
// parser maintains some mutable states of parsing.
//
// NOTE: The src member is assumed to be valid UF-8.
type parser struct {
srcName string
src string
pos int
overEOF int
errors []*Error
warn io.Writer
}
// Error is a parse error.
type Error = diag.Error[ErrorTag]
// ErrorTag parameterizes [diag.Error] to define [Error].
type ErrorTag struct{}
func (ErrorTag) ErrorTag() string { return "parse error" }
func parse[N Node](ps *parser, n N) parsed[N] {
begin := ps.pos
n.n().From = begin
n.parse(ps)
n.n().To = ps.pos
n.n().sourceText = ps.src[begin:ps.pos]
return parsed[N]{n}
}
type parsed[N Node] struct {
n N
}
func (p parsed[N]) addAs(ptr *N, parent Node) {
*ptr = p.n
addChild(parent, p.n)
}
func (p parsed[N]) addTo(ptr *[]N, parent Node) {
*ptr = append(*ptr, p.n)
addChild(parent, p.n)
}
func addChild(p Node, ch Node) {
p.n().addChild(ch)
ch.n().parent = p
}
// Tells the parser that parsing is done.
func (ps *parser) done() {
if ps.pos != len(ps.src) {
r, _ := utf8.DecodeRuneInString(ps.src[ps.pos:])
ps.error(fmt.Errorf("unexpected rune %q", r))
}
}
const eof rune = -1
func (ps *parser) peek() rune {
if ps.pos == len(ps.src) {
return eof
}
r, _ := utf8.DecodeRuneInString(ps.src[ps.pos:])
return r
}
func (ps *parser) hasPrefix(prefix string) bool {
return strings.HasPrefix(ps.src[ps.pos:], prefix)
}
func (ps *parser) next() rune {
if ps.pos == len(ps.src) {
ps.overEOF++
return eof
}
r, s := utf8.DecodeRuneInString(ps.src[ps.pos:])
ps.pos += s
return r
}
func (ps *parser) backup() {
if ps.overEOF > 0 {
ps.overEOF--
return
}
_, s := utf8.DecodeLastRuneInString(ps.src[:ps.pos])
ps.pos -= s
}
func (ps *parser) errorp(r diag.Ranger, e error) {
err := &Error{
Message: e.Error(),
Context: *diag.NewContext(ps.srcName, ps.src, r),
Partial: r.Range().From == len(ps.src),
}
ps.errors = append(ps.errors, err)
}
func (ps *parser) error(e error) {
end := ps.pos
if end < len(ps.src) {
end++
}
ps.errorp(diag.Ranging{From: ps.pos, To: end}, e)
}
// UnpackErrors returns the constituent parse errors if the given error contains
// one or more parse errors. Otherwise it returns nil.
func UnpackErrors(e error) []*Error {
if errs := diag.UnpackErrors[ErrorTag](e); len(errs) > 0 {
return errs
}
return nil
}
func newError(text string, shouldbe ...string) error {
if len(shouldbe) == 0 {
return errors.New(text)
}
var buf bytes.Buffer
if len(text) > 0 {
buf.WriteString(text + ", ")
}
buf.WriteString("should be " + shouldbe[0])
for i, opt := range shouldbe[1:] {
if i == len(shouldbe)-2 {
buf.WriteString(" or ")
} else {
buf.WriteString(", ")
}
buf.WriteString(opt)
}
return errors.New(buf.String())
}
|
