Curriculum Foundations Compiler feedback exercise 7 · mcq-explain

Compiler feedback

rustc emits warning: unused variable: extra but the program STILL compiles and runs. Pick the statement that correctly describes the warning-vs-error distinction.

Warnings produce output but don't stop compilation; the binary still builds and runs.

Warnings only appear in release builds; debug builds are silent.

Warnings stop the build until the underlying issue is fixed.

Warnings are turned into errors by default; you must rename the variable to _extra.

About this theme

Rust is learned with the compiler, not around it. Before ownership starts, learners need the habit of reading error[E...], spans, notes, and help: suggestions. Planned exercises: 1. identify the primary error line. 2. recognise a help: suggestion. 3. choose the fix for a type mismatch. 4. fill a corrected variable name. 5. fill a corrected type. 6. apply a compiler hint to one line. 7. explain why a warning is not an error. 8. fix a short program from a rustc diagnostic. 9. use the diagnostic to repair a function.