Rustc should warn, not fail on bad doc comments

[Manishearth]

source

The following MWE fails to compile with error: expected item after doc comment

fn main(){
}

/// Hi

this one fails to compile with a generic unexpected token: /// some input

fn main(){

}

fn foo(
  /// some input
  x: u8
  ) {

}

Comments should be ignored by the compiler, even doc comments. It makes sense to sanity-check comments during compilation, but can this be a warning instead of an error? In general, the /// token should be treated as a comment after perhaps linting for doc comment correctness.

[lifthrasiir]

Related to #2789.

[steveklabnik]

This is a language semantic and so would need an RFC to change. Please persue one if you still feel strongly abou tthis.