Incremental parsing creates error node when fresh parse doesn't

[casouri]

I'm not sure if this is a tree-sitter-haskell bug or tree-sitter bug; but as a start I decide to report it here.

Here's what I did:

At the beginning, there's this file:

f x =
              let a = 2
                  c = 1
 in a

I create a parser and parse it, got a parse tree.

Then I edit the file, indent the second and third lines:

f x =
  let a = 2
      c = 1
 in a

I parse the file again incrementally. Now the parse tree I get has an error node in it, even though the source code is syntactically correct.

More over, if I now create a fresh parser, and parse the edited file anew, the parse tree I get is different from the one I got from incremental parsing, and it doesn't have any error nodes.

I created a reproduce repo at here: https://github.com/casouri/tree-sitter-haskell-repo

Running run.sh should clone and compile tree-sitter and tree-sitter-haskell, and compile and run recipe.c. Running it should print out the two parse tree I get, the first one from incremental parsing, the second one from a fresh parse.

Parse tree of edited file:
(haskell declarations: (declarations (function name: (variable) patterns: (patterns (variable)) match: (match expression: (let_in binds: (local_binds decl: (bind name: (variable) match: (match expression: (literal (integer))))) (ERROR (variable)) expression: (variable))))))

Parse tree of a fresh parse:
(haskell declarations: (declarations (function name: (variable) patterns: (patterns (variable)) match: (match expression: (let_in binds: (local_binds decl: (bind name: (variable) match: (match expression: (literal (integer)))) decl: (bind name: (variable) match: (match expression: (literal (integer))))) expression: (variable))))))