There were only some UI tests that covered this function.
Since there's more diagnostic work going on, I think it makes
sense to have this unit tested.
TokenStream::extend
Two new insta-stable impls in libproc_macro:
```rust
impl Extend<TokenTree> for TokenStream
impl Extend<TokenStream> for TokenStream
```
`proc_macro::TokenStream` already implements `FromIterator<TokenTree>` and `FromIterator<TokenStream>` so I elected to support the same input types for `Extend`.
**This commit reduces compile time of Serde derives by 60% (takes less than half as long to compile)** as measured by building our test suite:
```console
$ git clone https://github.com/serde-rs/serde
$ cd serde/test_suite
$ cargo check --tests --features proc-macro2/nightly
$ rm -f ../target/debug/deps/libtest_*.rmeta
$ time cargo check --tests --features proc-macro2/nightly
Before: 20.8 seconds
After: 8.6 seconds
```
r? @alexcrichton
The Generics now contain one Vec of an enum for the generic parameters,
rather than two separate Vec's for lifetime and type parameters.
Additionally, places that previously used Vec<LifetimeDef> now use
Vec<GenericParam> instead.
Add case insensitive comparison, besides Levenstein for DYM
Closes#46332
Draft version. The idea is that Levenstein does not work for some cases when we have multiple equal weights for strings. I didn't understand the case with `if found != name => Some(found)` so it means that new code does not work correctly yet.
At least now I think that we might return all maximal weights from levenstein and think about next cases in priority order:
1) There is exact match -> None
2) There is exact match, but case insensitive -> Some(match)
3) There is some match from levenstein -> Some(matches.take_any)
4) There is no match -> None
@estebank WDYT?
Add ..= to the parser
Add ..= to libproc_macro
Add ..= to ICH
Highlight ..= in rustdoc
Update impl Debug for RangeInclusive to ..=
Replace `...` to `..=` in range docs
Make the dotdoteq warning point to the ...
Add warning for ... in expressions
Updated more tests to the ..= syntax
Updated even more tests to the ..= syntax
Updated the inclusive_range entry in unstable book
