LC

Add Error Recovery: Skip Invalid Characters

medium6/8

Implement Keyword Recognition Using Hash Table Build a Finite Automaton (DFA) and Use It to Drive Your Lexer

Language

Compiler

2.0s Limit 256MB

Implementation

Implement error recovery in your lexer to handle invalid input gracefully.

Requirements:

Detect and skip invalid characters
Report errors with line and column numbers
Continue scanning after errors (don't stop at first error)
Handle unterminated strings and comments
Return ERROR tokens for invalid input
Provide helpful error messages
Test with various invalid inputs

Why This Matters

IDE language servers like rust-analyzer and clangd lex code that is broken almost all the time — you are mid-keystroke — so skipping invalid characters and resynchronizing is their normal mode of operation. Without lexer recovery, a single stray '@' would kill autocomplete for the whole file.

Hints

0 / 3 revealed

Validation Suite

main.c

Workspace 1.0