Attribute crate_name 

Specifies the name of the crate.

Written as an inner attribute at the top of the crate root, crate_name is used to specify the name of a crate.

#![crate_name = "my_crate"]

The crate name must not be empty, and must only contain Unicode alphanumeric or _ (U+005F) characters.

Note that the specified name must match the name given by the --crate-name flag.

error: `--crate-name` and `#[crate_name]` are required to match, but `cli_name` != `attr_name`
 --> main.rs:1:17
  |
1 | #![crate_name = "attr_name"]
  |                 ^^^^^^^^^^^

In a Cargo project the crate name is always passed as --crate-name, derived from the target name ([lib] name or [[bin]] name if set, otherwise [package] name for libraries and the primary binary, or the source file name for other binaries). The crate_name attribute is therefore redundant here: it adds nothing, and if it is present it must match Cargo’s name, otherwise rustc reports an error.

For more information, see the Reference on the crate_name attribute.