rust/src/librustc_error_codes/error_codes/E0124.md

A struct was declared with two fields having the same name.

Erroneous code example:

struct Foo {
    field1: i32,
    field1: i32, // error: field is already declared
}

Please verify that the field names have been correctly spelled. Example:

struct Foo {
    field1: i32,
    field2: i32, // ok!
}