Unfortunately, the diagnotic machinery does not cope well with an empty
span which can happen if the crate is empty, in which case we merely set
a spanless note.

Intrinsics can only be defined by the compiler.

Same checks are performed during name resolution, and all attributes go through name resolution now

Use `PostExpansionVisitor` directly instead

… r=RalfJung

Stabilise weak_ptr_eq

Implemented in rust-lang#55987.

Closes rust-lang#55981.

…ebank

Provide a span if main function is not present in crate

Unfortunately, the diagnostic machinery does not cope well with an empty
span which can happen if the crate is empty, in which case we merely set
a spanless note.

Tests are already updated for this change, so a dedicated test is not added.

Resolves rust-lang#36561.

…nsic, r=Centril

Ban non-extern rust intrinsics

Intrinsics can only be defined by the compiler.

Fixes rust-lang#36979

feature_gate: Remove dead code from attribute checking

rust-lang#63468 is merged, so all attributes go through name resolution now, so we can remove code that previously performed some checks for attributes not going through resolution.