bug: Parse errors with preprocessor conditionals

[alexle0nte]

Did you check existing issues?

• I have read all the tree-sitter docs if it relates to using the parser
• I have searched the existing issues of tree-sitter-cpp

Tree-Sitter CLI Version, if relevant (output of tree-sitter --version)

tree-sitter 0.25.3 (2a835ee029dca1c325e6f1c01dbce40396f6123e)

Describe the bug

When parsing code with preprocessor conditionals, the parse tree reports errors in valid code. For example, given the following snippet:

#include <iostream>
#define ONE

int main()
{
  int x =
#ifdef ONE
  1
#else
  2
#endif
  ;

  std::cout << x;

  return 0;
}

the following errors are reported:

(ERROR [5, 2] - [5, 9])
(ERROR [7, 2] - [7, 3])
(ERROR [9, 2] - [9, 3])

These errors seem to correspond to the int x = assignment and the conditional values 1 and 2, even though the code is syntactically valid.

Steps To Reproduce/Bad Parse Tree

1. Write the code above in a C++ file.
2. Run tree-sitter parse on the file.
3. Observe the obtained parse tree:

(translation_unit [0, 0] - [17, 0]
  (preproc_include [0, 0] - [1, 0]
    path: (system_lib_string [0, 9] - [0, 19]))
  (preproc_def [1, 0] - [2, 0]
    name: (identifier [1, 8] - [1, 11]))
  (function_definition [3, 0] - [16, 1]
    type: (primitive_type [3, 0] - [3, 3])
    declarator: (function_declarator [3, 4] - [3, 10]
      declarator: (identifier [3, 4] - [3, 8])
      parameters: (parameter_list [3, 8] - [3, 10]))
    body: (compound_statement [4, 0] - [16, 1]
      (ERROR [5, 2] - [5, 9]
        type: (primitive_type [5, 2] - [5, 5])
        (identifier [5, 6] - [5, 7]))
      (preproc_ifdef [6, 0] - [10, 6]
        name: (identifier [6, 7] - [6, 10])
        (ERROR [7, 2] - [7, 3]
          (number_literal [7, 2] - [7, 3]))
        alternative: (preproc_else [8, 0] - [8, 5])
        (ERROR [9, 2] - [9, 3]
          (number_literal [9, 2] - [9, 3])))
      (expression_statement [11, 2] - [11, 3])
      (expression_statement [13, 2] - [13, 17]
        (binary_expression [13, 2] - [13, 16]
          left: (qualified_identifier [13, 2] - [13, 11]
            scope: (namespace_identifier [13, 2] - [13, 5])
            name: (identifier [13, 7] - [13, 11]))
          right: (identifier [13, 15] - [13, 16])))
      (return_statement [15, 2] - [15, 11]
        (number_literal [15, 9] - [15, 10])))))

Expected Behavior/Parse Tree

The parser should correctly handle this code without generating errors.

Repro

#include <iostream>
#define ONE

int main()
{
  int x =
#ifdef ONE
  1
#else
  2
#endif
  ;

  std::cout << x;

  return 0;
}