feat(lexer): allows to use '`' inside law text

src/catala/surface/lexer.ml

@@ -554,7 +554,9 @@ let lex_law (lexbuf : lexbuf) : token =
         LAW_INCLUDE (Ast.PdfFile ((name, Pos.from_lpos pos), pages))
       else LAW_INCLUDE (Ast.CatalaFile (name, Pos.from_lpos pos))
   | Plus '#', Star white_space, Plus (Compl '\n'), Star white_space, '\n' -> get_law_heading lexbuf
-  | Plus (Compl ('#' | '`' | '>')) -> LAW_TEXT (Utf8.lexeme lexbuf)
+  | Plus (Compl ('#' | '`' | '>') | Rep ('`', 1 .. 2), Compl '`' | "```", (Plus white_space | '\n'))
+    ->
+      LAW_TEXT (Utf8.lexeme lexbuf)
   | _ -> raise_lexer_error (Pos.from_lpos prev_pos) prev_lexeme
 
 (** Entry point of the lexer, distributes to {!val: lex_code} or {!val: lex_law} depending of {!val:

tests/test_literate/good/output/test_spe_char.catala.Test.out

@@ -0,0 +1,2 @@
+[RESULT] Computation successful! Results:
+[RESULT] literate_parsing_is_ok = true

tests/test_literate/good/test_spe_char.catala

@@ -0,0 +1,26 @@
+## Law text should be able to contain '`'.
+
+This is a block of law text containing `.
+This allows to:
+
+* use `Markdown` code block inside `Catala` files,
+
+* _escape_ special characters such as `#` or `>`,
+
+* use Fenced Code Blocks:
+
+```
+let () = print_endline "Hello world!"
+```
+
+**Remark**: for Fenced Code Blocks, ``` must be followed by a space or a new line.
+
+```catala
+new scope Test :
+  param literate_parsing_is_ok content bool
+
+scope Test :
+  def literate_parsing_is_ok := true
+```
+
+Even after `Catala` code block.