chore: import upstream snapshot with attribution

parser/error.go

@@ -0,0 +1,42 @@
+package parser
+
+import (
+	"fmt"
+	"io"
+
+	"github.com/kashav/fsql/tokenizer"
+)
+
+// ErrUnexpectedToken represents an unexpected token error.
+type ErrUnexpectedToken struct {
+	Actual   tokenizer.TokenType
+	Expected tokenizer.TokenType
+}
+
+func (e *ErrUnexpectedToken) Error() string {
+	return fmt.Sprintf("expected %s; got %s", e.Expected.String(),
+		e.Actual.String())
+}
+
+// ErrUnknownToken represents an unknown token error.
+type ErrUnknownToken struct {
+	Raw string
+}
+
+func (e *ErrUnknownToken) Error() string {
+	return fmt.Sprintf("unknown token: %s", e.Raw)
+}
+
+// currentError returns the current error, based on the parser's current Token
+// and the previously expected TokenType (set in parser.expect).
+func (p *parser) currentError() error {
+	if p.current == nil {
+		return io.ErrUnexpectedEOF
+	}
+
+	if p.current.Type == tokenizer.Unknown {
+		return &ErrUnknownToken{Raw: p.current.Raw}
+	}
+
+	return &ErrUnexpectedToken{Actual: p.current.Type, Expected: p.expected}
+}