The SCCs of the region graph are not a reliable heuristic to use for blaming an interesting
constraint for diagnostics. For region errors, if the outlived region is `'static`, or the involved
types are invariant in their lifetiems, there will be cycles in the constraint graph containing both
the target region and the most interesting constraints to blame. To get better diagnostics in these
cases, this commit removes that heuristic.
```
error: trait object `dyn Send` cannot be used in patterns
--> $DIR/issue-70972-dyn-trait.rs:6:9
|
LL | const F: &'static dyn Send = &7u32;
| -------------------------- constant defined here
...
LL | F => panic!(),
| ^ trait object can't be used in patterns
```
Don't Suggest Labeling `const` and `unsafe` Blocks
Fixes#128604
Previously, both anonymous constant blocks (E.g. The labeled block
inside `['_'; 'block: { break 'block 1 + 2; }]`) and inline const
blocks (E.g. `const { ... }`) were considered to be the same
kind of blocks. This caused the compiler to incorrectly suggest
labeling both the blocks when only anonymous constant blocks can be
labeled.
This PR adds an other enum variant to `Context` so that both the
blocks can be handled appropriately.
Also, adds some doc comments and removes unnecessary `&mut` in a
couple of places.
Make `body_owned_by` return the `Body` instead of just the `BodyId`
fixes#125677
Almost all `body_owned_by` callers immediately called `body`, too, so just return `Body` directly.
This makes the inline-const query feeding more robust, as all calls to `body_owned_by` will now yield a body for inline consts, too.
I have not yet figured out a good way to make `tcx.hir().body()` return an inline-const body, but that can be done as a follow-up
THIR unsafety checking was getting a cycle of
function unsafety checking
-> building THIR for the function
-> evaluating pattern inline constants in the function
-> building MIR for the inline constant
-> checking unsafety of functions (so that THIR can be stolen)
This is fixed by not stealing THIR when generating MIR but instead when
unsafety checking.
This leaves an issue with pattern inline constants not being unsafety
checked because they are evaluated away when generating THIR.
To fix that we now represent inline constants in THIR patterns and
visit them in THIR unsafety checking.
