error[E0033]: type `&dyn SomeTrait` cannot be dereferenced
  --> $DIR/E0033-teach.rs:12:9
   |
LL |     let &invalid = trait_obj;
   |         ^^^^^^^^ type `&dyn SomeTrait` cannot be dereferenced
   |
   = note: This error indicates that a pointer to a trait type cannot be implicitly dereferenced by a pattern. Every trait defines a type, but because the size of trait implementors isn't fixed, this type has no compile-time size. Therefore, all accesses to trait types must be through pointers. If you encounter this error you should try to avoid dereferencing the pointer.
           
           You can read more about trait objects in the Trait Objects section of the Reference: https://doc.rust-lang.org/reference/types.html#trait-objects

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0033`.