Referencing a crate, module, or type path that cannot be found in scope.
Rust compiler error E0433 indicates that an identifier in a module path (e.g. `HashMap::new()`) cannot be resolved in current crate scopes.
Missing `use std::collections::HashMap;` import or forgetting to add a dependency to `Cargo.toml`.
1// Missing: use std::collections::HashMap;2 3fn main() {4 let mut map = HashMap::new(); // ERROR E0433: failed to resolve: use of undeclared type 'HashMap'5 map.insert("a", 1);6}1use std::collections::HashMap; // Added missing import2 3fn main() {4 let mut map = HashMap::new();5 map.insert("a", 1);6 println!("{:?}", map);7}Simulate standard system builds to trigger compiler trace records and track memory crashes locally.
`HashMap` is part of `std::collections`. Without importing it or using full path `std::collections::HashMap`, rustc cannot resolve the identifier.