Add literal pattern syntax and change tree structure syntax

- Literal patterns don't interpret the special characters of regular expressions.
  In other words, 'abc|def' matches only `abc|def`, not `abc` or `def`.
- Change tree structure syntax from '(...) to #(...).

1 files changed, 13 insertions, 2 deletions

diff --git a/spec/lexer_test.go b/spec/lexer_test.go
index 89553d0..569f278 100644
--- a/spec/lexer_test.go
+++ b/spec/lexer_test.go
@@ -32,18 +32,19 @@ func TestLexer_Run(t *testing.T) {
 	}{
 		{
 			caption: "the lexer can recognize all kinds of tokens",
-			src:     `id"terminal":|;#'()$1...`,
+			src:     `id"terminal"'.*+?|()[\':|;#()$1...#`,
 			tokens: []*token{
 				idTok("id"),
 				termPatTok("terminal"),
+				termPatTok(`\.\*\+\?\|\(\)\[\\`),
 				symTok(tokenKindColon),
 				symTok(tokenKindOr),
 				symTok(tokenKindSemicolon),
-				symTok(tokenKindDirectiveMarker),
 				symTok(tokenKindTreeNodeOpen),
 				symTok(tokenKindTreeNodeClose),
 				posTok(1),
 				symTok(tokenKindExpantion),
+				symTok(tokenKindDirectiveMarker),
 				newEOFToken(),
 			},
 		},
@@ -64,6 +65,16 @@ func TestLexer_Run(t *testing.T) {
 			},
 		},
 		{
+			caption: "a pattern must include at least one character",
+			src:     `""`,
+			err:     synErrEmptyPattern,
+		},
+		{
+			caption: "a literal pattern must include at least one character",
+			src:     `''`,
+			err:     synErrEmptyPattern,
+		},
+		{
 			caption: "the lexer can recognize newlines and combine consecutive newlines into one",
 			src:     "\u000A | \u000D | \u000D\u000A | \u000A\u000A \u000D\u000D \u000D\u000A\u000D\u000A",
 			tokens: []*token{