fix: concatenations where the last item is a command substitution with backticks

src/scanner.c

@@ -276,10 +276,24 @@ static bool scan(Scanner *scanner, TSLexer *lexer, const bool *valid_symbols) {
               lexer->lookahead == '<' || lexer->lookahead == ')' ||
               lexer->lookahead == '(' || lexer->lookahead == ';' ||
               lexer->lookahead == '&' || lexer->lookahead == '|' ||
-              lexer->lookahead == '`' ||
               (lexer->lookahead == '}' && valid_symbols[CLOSING_BRACE]) ||
               (lexer->lookahead == ']' && valid_symbols[CLOSING_BRACKET]))) {
             lexer->result_symbol = CONCAT;
+            // This sucks
+            if (lexer->lookahead == '`') {
+                lexer->mark_end(lexer);
+                advance(lexer);
+                while (lexer->lookahead != '`' && !lexer->eof(lexer)) {
+                    advance(lexer);
+                }
+                if (lexer->eof(lexer)) {
+                    return false;
+                }
+                if (lexer->lookahead == '`') {
+                    advance(lexer);
+                }
+                return iswspace(lexer->lookahead) || lexer->eof(lexer);
+            }
             return true;
         }
     }

test/corpus/literals.txt

@@ -390,6 +390,10 @@ echo `echo hi; echo there`
 echo $(echo $(echo hi))
 echo $(< some-file)
 
+# both of these are concatenations!
+echo `echo otherword`word
+echo word`echo otherword`
+
 --------------------------------------------------------------------------------
 
 (program
@@ -430,7 +434,28 @@ echo $(< some-file)
       (word))
     (command_substitution
       (file_redirect
-        (word)))))
+        (word))))
+  (comment)
+  (command
+    (command_name
+      (word))
+    (concatenation
+      (command_substitution
+        (command
+          (command_name
+            (word))
+          (word)))
+      (word)))
+  (command
+    (command_name
+      (word))
+    (concatenation
+      (word)
+      (command_substitution
+        (command
+          (command_name
+            (word))
+          (word))))))
 
 ================================================================================
 Process substitutions