Use a more targeted span when suggesting casting an `fn` item to an `fn` pointer.
```
error[E0308]: cannot coerce functions which must be inlined to function pointers
--> $DIR/cast.rs:10:33
|
LL | let _: fn(isize) -> usize = callee;
| ------------------ ^^^^^^ cannot coerce functions which must be inlined to function pointers
| |
| expected due to this
|
= note: expected fn pointer `fn(_) -> _`
found fn item `fn(_) -> _ {callee}`
= note: fn items are distinct from fn pointers
help: consider casting to a fn pointer
|
LL | let _: fn(isize) -> usize = callee as fn(isize) -> usize;
| +++++++++++++++++++++
```
```
error[E0308]: mismatched types
--> $DIR/fn-pointer-mismatch.rs:42:30
|
LL | let d: &fn(u32) -> u32 = foo;
| --------------- ^^^ expected `&fn(u32) -> u32`, found fn item
| |
| expected due to this
|
= note: expected reference `&fn(_) -> _`
found fn item `fn(_) -> _ {foo}`
help: consider using a reference
|
LL | let d: &fn(u32) -> u32 = &foo;
| +
```
Previously we'd point at the whole expression for replacement, instead of marking what was being added.
We could also modify the suggestions for `&(name as fn())`, but for that we require storing more accurate spans than we have now.
Adds `#[rustc_force_inline]` which is similar to always inlining but
reports an error if the inlining was not possible, and which always
attempts to inline annotated items, regardless of optimisation levels.
It can only be applied to free functions to guarantee that the MIR
inliner will be able to resolve calls.
