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Merged
git-hulk merged 2 commits into from
Jun 14, 2026
Merged

Rename lexer state to match what it holds #277

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7826a34
Rename lexer state to match what it holds
git-hulk Jun 11, 2026
f1199c9
Spell out current-token names: current(), currentTokenKind, currentToken
git-hulk Jun 12, 2026
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84 changes: 42 additions & 42 deletions parser/lexer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@ const (
TokenKindInt TokenKind = "<int>"
TokenKindFloat TokenKind = "<float>"
TokenKindString TokenKind = "<string>"
TokenKindDot = "."
TokenKindDot TokenKind = "."
TokenKindSingleEQ TokenKind = "="
TokenKindDoubleEQ TokenKind = "=="
TokenKindNE TokenKind = "!="
Expand Down Expand Up @@ -75,8 +75,8 @@ func (t *Token) ToString() string {
}

type lexerState struct {
current int
lastToken *Token
offset int // byte offset into input of the next unread character
currentToken *Token // current lookahead token; nil at end of input
}

type Lexer struct {
Expand All @@ -98,19 +98,19 @@ func (l *Lexer) restoreState(state lexerState) {
}

func (l *Lexer) skipN(n int) {
l.current += n
l.offset += n
}

func (l *Lexer) slice(i, j int) string {
return l.input[l.current+i : l.current+j]
return l.input[l.offset+i : l.offset+j]
}

func (l *Lexer) peekN(n int) byte {
return l.input[l.current+n]
return l.input[l.offset+n]
}

func (l *Lexer) peekOk(n int) bool {
return l.current+n < len(l.input)
return l.offset+n < len(l.input)
}

func (l *Lexer) isKeyword(ident string) bool {
Expand Down Expand Up @@ -165,11 +165,11 @@ func (l *Lexer) consumeNumber() error {
if (l.peekOk(i) && IsIdentPart(l.peekN(i))) || !hasNumberPart {
return errors.New("invalid number")
}
l.lastToken = &Token{
l.currentToken = &Token{
Kind: tokenKind,
String: l.slice(0, i),
Pos: Pos(l.current),
End: Pos(l.current + i),
Pos: Pos(l.offset),
End: Pos(l.offset + i),
Base: base,
}
l.skipN(i)
Expand Down Expand Up @@ -212,11 +212,11 @@ func (l *Lexer) consumeIdent(_ Pos) error {
} else {
token.Kind = TokenKindIdent
}
token.Pos = Pos(l.current)
token.End = Pos(l.current + i)
token.Pos = Pos(l.offset)
token.End = Pos(l.offset + i)
token.String = slice
token.QuoteType = quoteType
l.lastToken = token
l.currentToken = token

l.skipN(i)
if quoteType != Unquoted {
Expand Down Expand Up @@ -274,11 +274,11 @@ func (l *Lexer) consumeString() error {
if !l.peekOk(i) || l.peekN(i) != endChar {
return errors.New("invalid string")
}
l.lastToken = &Token{
l.currentToken = &Token{
Kind: TokenKindString,
String: l.slice(1, i),
Pos: Pos(l.current + 1),
End: Pos(l.current + i),
Pos: Pos(l.offset + 1),
End: Pos(l.offset + i),
}
l.skipN(i + 1)
return nil
Expand Down Expand Up @@ -317,7 +317,7 @@ func (l *Lexer) peekToken() (*Token, error) {
if err := l.consumeToken(); err != nil {
return nil, err
}
token := l.lastToken
token := l.currentToken

l.restoreState(savedState)
return token, nil
Expand All @@ -332,9 +332,9 @@ func (l *Lexer) hasPrecedenceToken(last *Token) bool {
}

func (l *Lexer) consumeToken() error {
// clear last token
lastToken := l.lastToken
l.lastToken = nil
// replace the current token; keep the previous one to disambiguate unary +/-
prevToken := l.currentToken
l.currentToken = nil
l.skipComments()
l.skipSpace()
if l.isEOF() {
Expand All @@ -346,82 +346,82 @@ func (l *Lexer) consumeToken() error {
l.peekN(0) == '<' && l.peekOk(1) && l.peekN(1) == '>' || // <>
l.peekN(0) == '=' && l.peekOk(1) && l.peekN(1) == '=' || // ==
l.peekN(0) != '|' && l.peekOk(1) && l.peekN(1) == '=' { // |=
l.lastToken = &Token{
l.currentToken = &Token{
String: l.slice(0, 2),
Kind: TokenKind(l.slice(0, 2)),
Pos: Pos(l.current),
End: Pos(l.current + 2),
Pos: Pos(l.offset),
End: Pos(l.offset + 2),
}
l.skipN(2)
return nil
}

case '+', '-':
// hasPrecedenceToken is used to distinguish between unary and binary operators
if !l.hasPrecedenceToken(lastToken) && l.peekOk(1) && IsDigit(l.peekN(1)) {
if !l.hasPrecedenceToken(prevToken) && l.peekOk(1) && IsDigit(l.peekN(1)) {
return l.consumeNumber()
} else if l.peekOk(1) && l.peekN(1) == '>' {
l.lastToken = &Token{
l.currentToken = &Token{
String: l.slice(0, 2),
Kind: TokenKindArrow,
Pos: Pos(l.current),
End: Pos(l.current + 2),
Pos: Pos(l.offset),
End: Pos(l.offset + 2),
}
l.skipN(2)
return nil
}
case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
return l.consumeNumber()
case '`', '$', '"':
return l.consumeIdent(Pos(l.current))
return l.consumeIdent(Pos(l.offset))
case '\'':
return l.consumeString()
case ':':
if l.peekOk(1) && l.peekN(1) == ':' {
l.lastToken = &Token{
l.currentToken = &Token{
String: l.slice(0, 2),
Kind: TokenKindDash,
Pos: Pos(l.current),
End: Pos(l.current + 2),
Pos: Pos(l.offset),
End: Pos(l.offset + 2),
}
l.skipN(2)
return nil
}
case '.':
l.lastToken = &Token{
l.currentToken = &Token{
String: l.slice(0, 1),
Kind: TokenKindDot,
Pos: Pos(l.current),
End: Pos(l.current + 1),
Pos: Pos(l.offset),
End: Pos(l.offset + 1),
}
l.skipN(1)
return nil
}

if IsIdentStart(l.peekN(0)) {
return l.consumeIdent(Pos(l.current))
return l.consumeIdent(Pos(l.offset))
}

token := &Token{}
token.Pos = Pos(l.current)
token.End = Pos(l.current + 1)
token.String = l.input[l.current : l.current+1]
token.Pos = Pos(l.offset)
token.End = Pos(l.offset + 1)
token.String = l.input[l.offset : l.offset+1]
token.Kind = TokenKind(token.String)
l.skipN(1)
l.lastToken = token
l.currentToken = token
return nil
}

func (l *Lexer) isEOF() bool {
return l.current >= len(l.input)
return l.offset >= len(l.input)
}

func (l *Lexer) skipSpace() {
for !l.isEOF() {
r, size := utf8.DecodeRuneInString(l.input[l.current:])
r, size := utf8.DecodeRuneInString(l.input[l.offset:])
if !unicode.IsSpace(r) {
break
}
l.current += size
l.offset += size
}
}
42 changes: 21 additions & 21 deletions parser/lexer_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ func TestConsumeComment(t *testing.T) {

// TestConsumeUnterminatedComment guards against an infinite loop (a DoS hang)
// when a block comment is never closed. consumeMultiLineComment previously
// looped on isEOF() while only advancing a local index, so l.current never
// looped on isEOF() while only advancing a local index, so l.offset never
// reached EOF and the lexer spun forever. The test runs in a goroutine with a
// timeout so a regression fails fast instead of hanging the whole test binary.
func TestConsumeUnterminatedComment(t *testing.T) {
Expand Down Expand Up @@ -74,8 +74,8 @@ func TestConsumeString(t *testing.T) {
lexer := NewLexer(s)
err := lexer.consumeToken()
require.NoError(t, err)
require.Equal(t, TokenKindString, lexer.lastToken.Kind)
require.Equal(t, strings.Trim(s, "'"), lexer.lastToken.String)
require.Equal(t, TokenKindString, lexer.currentToken.Kind)
require.Equal(t, strings.Trim(s, "'"), lexer.currentToken.String)
require.True(t, lexer.isEOF())
}
})
Expand All @@ -93,8 +93,8 @@ func TestConsumeString(t *testing.T) {
lexer := NewLexer(tc.input)
err := lexer.consumeToken()
require.NoError(t, err, "Failed to parse: %s", tc.input)
require.Equal(t, TokenKindString, lexer.lastToken.Kind)
require.Equal(t, tc.expected, lexer.lastToken.String)
require.Equal(t, TokenKindString, lexer.currentToken.Kind)
require.Equal(t, tc.expected, lexer.currentToken.String)
require.True(t, lexer.isEOF())
}
})
Expand All @@ -112,8 +112,8 @@ func TestConsumeString(t *testing.T) {
lexer := NewLexer(tc.input)
err := lexer.consumeToken()
require.NoError(t, err, "Failed to parse: %s", tc.input)
require.Equal(t, TokenKindString, lexer.lastToken.Kind)
require.Equal(t, tc.expected, lexer.lastToken.String)
require.Equal(t, TokenKindString, lexer.currentToken.Kind)
require.Equal(t, tc.expected, lexer.currentToken.String)
require.True(t, lexer.isEOF())
}
})
Expand All @@ -130,8 +130,8 @@ func TestConsumeString(t *testing.T) {
lexer := NewLexer(tc.input)
err := lexer.consumeToken()
require.NoError(t, err, "Failed to parse: %s", tc.input)
require.Equal(t, TokenKindString, lexer.lastToken.Kind)
require.Equal(t, tc.expected, lexer.lastToken.String)
require.Equal(t, TokenKindString, lexer.currentToken.Kind)
require.Equal(t, tc.expected, lexer.currentToken.String)
require.True(t, lexer.isEOF())
}
})
Expand All @@ -152,9 +152,9 @@ func TestConsumeNumber(t *testing.T) {
lexer := NewLexer(i)
err := lexer.consumeToken()
require.NoError(t, err)
require.Equal(t, TokenKindInt, lexer.lastToken.Kind)
require.Equal(t, 10, lexer.lastToken.Base)
require.Equal(t, i, lexer.lastToken.String)
require.Equal(t, TokenKindInt, lexer.currentToken.Kind)
require.Equal(t, 10, lexer.currentToken.Base)
require.Equal(t, i, lexer.currentToken.String)
require.True(t, lexer.isEOF())
}
})
Expand All @@ -168,9 +168,9 @@ func TestConsumeNumber(t *testing.T) {
lexer := NewLexer(n)
err := lexer.consumeToken()
require.NoError(t, err)
require.Equal(t, TokenKindInt, lexer.lastToken.Kind)
require.Equal(t, 16, lexer.lastToken.Base)
require.Equal(t, n, lexer.lastToken.String)
require.Equal(t, TokenKindInt, lexer.currentToken.Kind)
require.Equal(t, 16, lexer.currentToken.Base)
require.Equal(t, n, lexer.currentToken.String)
require.True(t, lexer.isEOF())
}
})
Expand Down Expand Up @@ -208,8 +208,8 @@ func TestConsumeNumber(t *testing.T) {
lexer := NewLexer(f)
err := lexer.consumeToken()
require.NoError(t, err)
require.Equal(t, TokenKindFloat, lexer.lastToken.Kind)
require.Equal(t, f, lexer.lastToken.String)
require.Equal(t, TokenKindFloat, lexer.currentToken.Kind)
require.Equal(t, f, lexer.currentToken.String)
require.True(t, lexer.isEOF())
}
})
Expand Down Expand Up @@ -258,8 +258,8 @@ func TestConsumeNumber(t *testing.T) {
lexer := NewLexer(i)
err := lexer.consumeToken()
require.NoError(t, err)
require.Equal(t, TokenKindIdent, lexer.lastToken.Kind)
require.Equal(t, strings.Trim(i, "`"), lexer.lastToken.String)
require.Equal(t, TokenKindIdent, lexer.currentToken.Kind)
require.Equal(t, strings.Trim(i, "`"), lexer.currentToken.String)
require.True(t, lexer.isEOF())
}
})
Expand All @@ -269,8 +269,8 @@ func TestConsumeNumber(t *testing.T) {
lexer := NewLexer(k)
err := lexer.consumeToken()
require.NoError(t, err)
require.Equal(t, TokenKindKeyword, lexer.lastToken.Kind)
require.Equal(t, k, lexer.lastToken.String)
require.Equal(t, TokenKindKeyword, lexer.currentToken.Kind)
require.Equal(t, k, lexer.currentToken.String)
require.True(t, lexer.isEOF())
}
})
Expand Down
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