error[E0259]: the name `m1` is defined multiple times
  --> $DIR/extern-crate-rename.rs:16:1
   |
LL | extern crate m1;
   | ---------------- previous import of the extern crate `m1` here
LL | extern crate m2 as m1; //~ ERROR is defined multiple times
   | ^^^^^^^^^^^^^^^^^^^^^^
   | |
   | `m1` reimported here
   | You can use `as` to change the binding name of the import
   |
   = note: `m1` must be defined only once in the type namespace of this module

error: aborting due to previous error

For more information about this error, try `rustc --explain E0259`.