1 An undeclared type or module was used.
3 Erroneous code example:
6 let map = HashMap::new();
7 // error: failed to resolve: use of undeclared type or module `HashMap`
10 Please verify you didn't misspell the type/module's name or that you didn't
15 use std::collections::HashMap; // HashMap has been imported.
16 let map: HashMap<u32, u32> = HashMap::new(); // So it can be used!