error[E0119]: conflicting implementations of trait `From<(_,)>` for type `(_,)`
  --> $DIR/coherence-overlap-all-t-and-tuple.rs:16:1
   |
LL | impl <T> From<T> for T {
   | ---------------------- first implementation here
...
LL | impl <T11, U11> From<(U11,)> for (T11,) {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(_,)`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0119`.