Add a comment for disabling errexit, try to debug appveyor cache
Comments added as requested.
Also, lets add some cache debugging to appveyor. I *think* this is how to ignore errors in cmd.exe (and I did try it on my own machine), but I'm not 100% sure how appveyor runs them. In the worst case it'll fail but I guess that isn't the end of the world since the build has already failed by this point.
r? @TimNN
Specialize Vec::from_elem to use calloc
Fixes#38723. This specializes the implementation for `u8` only, but it could be extended to other zeroable types if desired.
I haven't tested this extensively, but I did verify that it gives the expected performance boost for large `vec![0; n]` allocations with both alloc_system and jemalloc, on Linux. (I have not tested or even built the Windows code.)
[rustbuild] Side-step HashMap iteration to preserve command-line step order.
The new `HashMap` was introduced by #41227 and it accidentally randomized step order.
r? @alexcrichton
Part of #29368.
* added missing links
* updated method summaries to use 3rd person style
* added missing periods in `Component`'s variant summaries
* use standard iterator boilerplate in `Components`' and `Iter`'s docs
* added example to `Iter::as_path`, adapted from `Components::as_path`'s
example
* consolidated examples for `Path::file_name`
* some other small fixes
rustc: provide adt_sized_constraint as an on-demand query.
By using `queries::adt_sized_constraint::try_get`, we can detect cycles without a separate stack.
r? @nikomatsakis
add 'mir' to rustc help menu and man doc
add 'mir' to '--emit' flag list for 'rustc'.
This is added because 'rustc' can now generate MIR (referencing to
"Teach rustc --emit=mir #39891").
Do not desugar if-let-else to match arm guards
Fixes#41272
Changed the desugaring code
**Before**
```rust
match <sub_expr> {
<pat> => <body>,
[_ if <else_opt_if_cond> => <else_opt_if_body>,]
_ => [<else_opt> | ()]
}
```
**After**
```rust
match <sub_expr> {
<pat> => <body>,
_ => [<else_opt> | ()]
}
```
With this fix, it doesn't cause E0301
