Change the lexical specs of regexp and define concrete syntax error values

* Make the lexer treat ']' as an ordinary character in default mode
* Define values of the syntax error type that represents error information concretely

1 files changed, 37 insertions, 0 deletions

diff --git a/compiler/syntax_error.go b/compiler/syntax_error.go
new file mode 100644
index 0000000..be2dc38
--- /dev/null
+++ b/compiler/syntax_error.go
@@ -0,0 +1,37 @@
+package compiler
+
+import "fmt"
+
+type SyntaxError struct {
+	Message string
+}
+
+func newSyntaxError(msg string) *SyntaxError {
+	return &SyntaxError{
+		Message: msg,
+	}
+}
+
+func (e *SyntaxError) Error() string {
+	return fmt.Sprintf("syntax error: %s", e.Message)
+}
+
+var (
+	// lexical errors
+	synErrIncompletedEscSeq = newSyntaxError("incompleted escape sequence; unexpected EOF following \\")
+	synErrInvalidEscSeq     = newSyntaxError("invalid escape sequence")
+
+	// syntax errors
+	synErrUnexpectedToken   = newSyntaxError("unexpected token")
+	synErrNullPattern       = newSyntaxError("a pattern must be a non-empty byte sequence")
+	synErrAltLackOfOperand  = newSyntaxError("an alternation expression must have operands")
+	synErrRepNoTarget       = newSyntaxError("a repeat expression must have an operand")
+	synErrGroupNoElem       = newSyntaxError("a grouping expression must include at least one character")
+	synErrGroupUnclosed     = newSyntaxError("unclosed grouping expression")
+	synErrGroupNoInitiator  = newSyntaxError(") needs preceding (")
+	synErrGroupInvalidForm  = newSyntaxError("invalid grouping expression")
+	synErrBExpNoElem        = newSyntaxError("a bracket expression must include at least one character")
+	synErrBExpUnclosed      = newSyntaxError("unclosed bracket expression")
+	synErrBExpInvalidForm   = newSyntaxError("invalid bracket expression")
+	synErrRangeInvalidOrder = newSyntaxError("a range expression with invalid order")
+)