Because of type inference, duplicate obligations exist and cause duplicate
errors. To avoid this, only display the first error for each (predicate,span).
The inclusion of the span is somewhat bikesheddy, but *is* the more
conservative option (it does not remove some instability, as duplicate
obligations are ignored by `duplicate_set` under some inference conditions).
Fixes#28098
cc #21528 (is it a dupe?)
This PR removes random remaining `Ident`s outside of libsyntax and performs general cleanup
In particular, interfaces of `Name` and `Ident` are tidied up, `Name`s and `Ident`s being small `Copy` aggregates are always passed to functions by value, and `Ident`s are never used as keys in maps, because `Ident` comparisons are tricky.
Although this PR closes https://github.com/rust-lang/rust/issues/6993 there's still work related to it:
- `Name` can be made `NonZero` to compress numerous `Option<Name>`s and `Option<Ident>`s but it requires const unsafe functions.
- Implementation of `PartialEq` on `Ident` should be eliminated and replaced with explicit hygienic, non-hygienic or member-wise comparisons.
- Finally, large parts of AST can potentially be converted to `Name`s in the same way as HIR to clearly separate identifiers used in hygienic and non-hygienic contexts.
r? @nrc
Make sure Name, SyntaxContext and Ident are passed by value
Make sure Idents don't serve as keys (or parts of keys) in maps, Ident comparison is not well defined
Part of https://github.com/rust-lang/rust/issues/6993
This patch replaces `Ident`s with `Name`s in data structures of HIR and updates the dependent crates to compile and pass `make check`.
Some HIR structures still use `Ident`s, namely `PathSegment`, `PatIdent`, `ExprWhile`, `ExprLoop`, `ExprBreak` and `ExprAgain`, they need them for resolve (but `PathSegment` is special, see https://github.com/rust-lang/rust/issues/6993#issuecomment-141256292).
r? @nrc
Fixes#28279.
Currently
`common_supertype(*mut for<'a> Fn(&'a usize), *mut for<'a> Fn(&'a usize) + 'static)`
equals `*mut Fn(&usize)` which seems to be caused by `higher_ranked_sub()` allowing region variables to escape the comparison. This prevents inference from working properly with stuff like `Rc<Fn(&T)>`.
r? @nikomatsakis
new error style:
```
path.rs:4:6: 4:7 error: the trait `core::marker::Sized` is not implemented for the type `[u8]` [E0277]
path.rs:4 fn f(p: Path) {}
^
path.rs:4:6: 4:7 help: run `rustc --explain E0277` to see a detailed explanation
path.rs:4:6: 4:7 note: `[u8]` does not have a constant size known at compile-time
path.rs:4:6: 4:7 note: required because it appears within the type `std::sys::os_str::Slice`
path.rs:4:6: 4:7 note: required because it appears within the type `std::ffi::os_str::OsStr`
path.rs:4:6: 4:7 note: required because it appears within the type `std::path::Path`
path.rs:4:6: 4:7 note: all local variables must have a statically known size
path.rs:7:5: 7:36 error: the trait `core::marker::Send` is not implemented for the type `alloc::rc::Rc<()>` [E0277]
path.rs:7 foo::<BTreeMap<Rc<()>, Rc<()>>>();
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
path.rs:7:5: 7:36 help: run `rustc --explain E0277` to see a detailed explanation
path.rs:7:5: 7:36 note: `alloc::rc::Rc<()>` cannot be sent between threads safely
path.rs:7:5: 7:36 note: required because it appears within the type `collections::btree::node::Node<alloc::rc::Rc<()>, alloc::rc::Rc<()>>`
path.rs:7:5: 7:36 note: required because it appears within the type `collections::btree::map::BTreeMap<alloc::rc::Rc<()>, alloc::rc::Rc<()>>`
path.rs:7:5: 7:36 note: required by `foo`
error: aborting due to 2 previous errors
```
Fixes#21793Fixes#23286
r? @nikomatsakis
The sort key is a (DefId, Name), which is *not* stable between
runs, so we must re-sort when loading.
Fixes#24063Fixes#25467Fixes#27222Fixes#28377
r? @eddyb
new error style:
```
path.rs:4:6: 4:7 error: the trait `core::marker::Sized` is not implemented for the type `[u8]` [E0277]
path.rs:4 fn f(p: Path) {}
^
path.rs:4:6: 4:7 help: run `rustc --explain E0277` to see a detailed explanation
path.rs:4:6: 4:7 note: `[u8]` does not have a constant size known at compile-time
path.rs:4:6: 4:7 note: required because it appears within the type `std::sys::os_str::Slice`
path.rs:4:6: 4:7 note: required because it appears within the type `std::ffi::os_str::OsStr`
path.rs:4:6: 4:7 note: required because it appears within the type `std::path::Path`
path.rs:4:6: 4:7 note: all local variables must have a statically known size
path.rs:7:5: 7:36 error: the trait `core::marker::Send` is not implemented for the type `alloc::rc::Rc<()>` [E0277]
path.rs:7 foo::<BTreeMap<Rc<()>, Rc<()>>>();
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
path.rs:7:5: 7:36 help: run `rustc --explain E0277` to see a detailed explanation
path.rs:7:5: 7:36 note: `alloc::rc::Rc<()>` cannot be sent between threads safely
path.rs:7:5: 7:36 note: required because it appears within the type `collections::btree::node::Node<alloc::rc::Rc<()>, alloc::rc::Rc<()>>`
path.rs:7:5: 7:36 note: required because it appears within the type `collections::btree::map::BTreeMap<alloc::rc::Rc<()>, alloc::rc::Rc<()>>`
path.rs:7:5: 7:36 note: required by `foo`
error: aborting due to 2 previous errors
```
This improves the #21793/#23286 situation
