1 files changed, 22 insertions, 0 deletions
diff --git a/grammar/semantic_error.go b/grammar/semantic_error.go
new file mode 100644
index 0000000..01446ed
--- /dev/null
+++ b/grammar/semantic_error.go
@@ -0,0 +1,22 @@
+package grammar
+
+type SemanticError struct {
+	message string
+}
+
+func newSemanticError(message string) *SemanticError {
+	return &SemanticError{
+		message: message,
+	}
+}
+
+func (e *SemanticError) Error() string {
+	return e.message
+}
+
+var (
+	semErrNoProduction    = newSemanticError("a grammar needs at least one production")
+	semErrUndefinedSym    = newSemanticError("undefined symbol")
+	semErrDirInvalidName  = newSemanticError("invalid directive name")
+	semErrDirInvalidParam = newSemanticError("invalid parameter")
+)