On return type `impl Trait` for block with no expr point at last semi
Partial solution, doesn't actually validate that the last statement in the function body can satisfy the trait bound, but it's a good incremental improvement over the status quo.
```
error[E0277]: the trait bound `(): Bar` is not satisfied
--> $DIR/impl-trait-return-trailing-semicolon.rs:3:13
|
LL | fn foo() -> impl Bar {
| ^^^^^^^^ the trait `Bar` is not implemented for `()`
LL | 5;
| - consider removing this semicolon
|
= note: the return type of a function must have a statically known size
```
Partially addresses #54771.
Create a derive macro for HashStable and allow proc macros in rustc
A combination of https://github.com/rust-lang/rust/pull/56864 and https://github.com/rust-lang/rust/pull/56795. There were complications with using `serde_derive` as rustc doesn't know which crate to use for the host when there is a serde_derive in the sysroot and cargo passes another on the command line built from crates.io.
r? @eddyb (for proc macro changes) @alexcrichton (for rustbuild changes) @michaelwoerister (for the macro itself)
```
error[E0317]: if may be missing an else clause
--> $DIR/if-without-else-as-fn-expr.rs:2:5
|
LL | fn foo(bar: usize) -> usize {
| ----- found `usize` because of this return type
LL | / if bar % 5 == 0 {
LL | | return 3;
LL | | }
| |_____^ expected (), found usize
|
= note: expected type `()`
found type `usize`
= note: `if` expressions without `else` must evaluate to `()`
```
`va_start` and `va_end` must be called to initialize/cleanup the
"spoofed" `VaList` in a Rust defined C-variadic function even if
the `VaList` is not used.
`-Z treat-err-as-bug=0` will cause `rustc` to panic after the first
error is reported. `-Z treat-err-as-bug=2` will cause `rustc` to
panic after 3 errors have been reported.
Add const generics to ty (and transitive dependencies)
Split out from #53645. This work is a collaborative effort with @yodaldevoid.
There are a number of stubs. Some I plan to leave for the next PRs (e.g. `infer` and `rustdoc`). Others I can either fix up in this PR, or as follow ups (which would avoid the time-consuming rebasing).
It was a little hard to split this up, as so much depends on ty and friends. Apologies for the large diff.
r? @eddyb
