Semantic Error Reporting

Good Errors Save Developer Time

Rust's mismatched types with expected/found labels, Clang's caret diagnostics, and Elm's friendly errors all come from deliberate semantic error design. A compiler that prints error with no location or context is worse than no compiler at all.

Error Message Anatomy

Include: what went wrong, where (file, line, column), and often a hint. Use consistent formatting. Continue after non-fatal errors to report multiple issues. Attach notes for related locations (declaration site vs use site).

cCopy
Loading…

• Categorize: type error, undefined name, wrong arity
• Print line numbers from token/AST locations
• Suggest fixes when possible (did you mean foo?)
• Increment error count; abort compilation only if fatal

Connecting to real compilers

Production compilers embed this step inside a longer pipeline. GCC flows through cpp, cc1, assembly, and ld; Clang uses the driver, Sema, LLVM IR passes, and a target backend. LLVM bitcode, JVM bytecode, and WASM are other familiar IRs at the same layer. The exercise isolates one pass so you can test it alone before chaining it to the next stage.

Why for this exercise

You will implement semantic error reporting with clear messages and source locations. This exercise asks you to format type and scope errors so users can fix their code without guessing what the compiler meant.