This fixes `issue-28848.rs` -- it also handles another case that the
AST region checker gets wrong (`wf-self-type.rs`). I don't actually
think that this is the *right way* to be enforcing this constraint --
I think we should probably do it more generally, perhaps by editing
`predicates_of` for the impl itself. The chalk-style implied bounds
setup ought to fix this.
This gives at least some explanation for why a borrow is expected to
last for a certain free region. Also:
* Reports E0373: "closure may outlive the current function" with NLL.
* Special cases the case of returning a reference to (or value
referencing) a local variable or temporary (E0515).
* Special case assigning a reference to a local variable in a closure
to a captured variable.
Adds UseAsConst and UseAsStatic to replace Return in consts/statics.
Don't report the arguments to an overloaded operator as CallArguments.
Also don't report "escaping data" in these items.
Prefer unwrap_or_else to unwrap_or in case of function calls/allocations
The contents of `unwrap_or` are evaluated eagerly, so it's not a good pick in case of function calls and allocations. This PR also changes a few `unwrap_or`s with `unwrap_or_default`.
An added bonus is that in some cases this change also reveals if the object it's called on is an `Option` or a `Result` (based on whether the closure takes an argument).
handle underscore bounds in unexpected places
Per the discussion on #54902, I made it a hard error to use lifetime bounds in various places where they used to be permitted:
- `where Foo: Bar<'_>` for example
I also moved error reporting to HIR lowering and added `Error` variants to let us suppress downstream errors that result.
I (imo) improved the error message wording to be clearer, as well.
In the process, I fixed the ICE in #52098.
Fixes#54902Fixes#52098
At some point, I had thought to use this code to handle equality
comparisons for the `IfEq` verify bounds; at that point, we might not
have had an infcx to talk about. But we wound up doing "SCC
representatives" instead, so that's fine.
Instead, we talk about:
- creating the "next" universe
- universes "extending" one another
- and `u1.can_name(u2)`, meaning that `u1` contains all names from `u2`
[NLL] Check user types are well-formed
Also contains a change of span for AscribeUserType.
I'm not quite sure if this was what @nikomatsakis was thinking.
Closes#54620
r? @nikomatsakis
Better Diagnostic for Trait Object Capture
Part of #52663.
This commit enhances `LaterUseKind` detection to identify when a borrow
is captured by a trait object which helps explain why there is a borrow
error.
r? @nikomatsakis
cc @pnkfelix
Now when a `FnMut` closure is returning a closure that contains a
reference to a captured variable, we provide an error that makes it more
clear what is happening.
