bug: #ifdef causes "else" to be treated as error

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
cpp
Domain
compilers

Research direction

Start by loading the provided C++ reproduction in the Tree-sitter Playground (0.23.4?) and compare its bad parse tree with the expected behavior. Trace how preproc_ifdef and if_statement interact around the conditional else; done means the reproduction no longer marks else as ERROR and the resulting tree preserves the intended branches.

Written by the indexing model from the issue text.

Description

bug
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)

Playground (0.23.4?)

Describe the bug

When "interrupting" an if/else with an #ifdef then the else is treated as an error. This might be tricky to turn into a proper tree, as the "ifdef" can separate the "else" branch content from the "if".

Steps To Reproduce/Bad Parse Tree
translation_unit [0, 0] - [6, 0]
  preproc_ifdef [0, 0] - [4, 6]
    name: identifier [0, 7] - [0, 20]
    if_statement [1, 1] - [2, 8]
      condition: condition_clause [1, 4] - [1, 9]
        value: identifier [1, 5] - [1, 8]
      consequence: expression_statement [2, 2] - [2, 8]
        call_expression [2, 2] - [2, 7]
          function: identifier [2, 2] - [2, 5]
          arguments: argument_list [2, 5] - [2, 7]
    ERROR [3, 1] - [3, 5]
  expression_statement [5, 2] - [5, 8]
    call_expression [5, 2] - [5, 7]
      function: identifier [5, 2] - [5, 5]
      arguments: argument_list [5, 5] - [5, 7]
Expected Behavior/Parse Tree

A solution might be difficult to do with the current structure. Here's a workaround that would preserve the logic and could be supported with the current structure. Maybe it could be treated like that automatically?

#ifdef DO_THIS_CHECK
	if (bar)
		baz();
	else
		qux();
#else
 	qux();
#endif
Repro
#ifdef DO_THIS_CHECK
	if (bar)
		baz();
	else
#endif
		qux();
Dominant language
JavaScript
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Forks
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