Add comment about why JS and JSX are handled with the TSX parser

Author: maxbrunsfeld

src/Parsing/Parser.hs

@@ -191,9 +191,13 @@ someASTParser :: Language -> Maybe SomeASTParser
 someASTParser Go         = Just (SomeASTParser (ASTParser tree_sitter_go :: Parser (AST [] Go.Grammar)))
 someASTParser Haskell    = Just (SomeASTParser (ASTParser tree_sitter_haskell :: Parser (AST [] Haskell.Grammar)))
 someASTParser Java       = Just (SomeASTParser (ASTParser tree_sitter_java :: Parser (AST [] Java.Grammar)))
-someASTParser JavaScript = Just (SomeASTParser (ASTParser tree_sitter_tsx :: Parser (AST [] TSX.Grammar)))
 someASTParser JSON       = Just (SomeASTParser (ASTParser tree_sitter_json :: Parser (AST [] JSON.Grammar)))
+
+-- Use the TSX parser for `.js` and `.jsx` files in case they use Flow type-annotation syntax.
+-- The TSX and Flow syntaxes are the same, whereas the normal TypeScript syntax is different.
+someASTParser JavaScript = Just (SomeASTParser (ASTParser tree_sitter_tsx :: Parser (AST [] TSX.Grammar)))
 someASTParser JSX        = Just (SomeASTParser (ASTParser tree_sitter_tsx :: Parser (AST [] TSX.Grammar)))
+
 someASTParser Python     = Just (SomeASTParser (ASTParser tree_sitter_python :: Parser (AST [] Python.Grammar)))
 someASTParser Ruby       = Just (SomeASTParser (ASTParser tree_sitter_ruby :: Parser (AST [] Ruby.Grammar)))
 someASTParser TypeScript = Just (SomeASTParser (ASTParser tree_sitter_typescript :: Parser (AST [] TypeScript.Grammar)))