This allows builtin derives to be registered and
resolved, just like other derive types.

The old code created a flat listing of "HIR -> WorkProduct" edges.
While perfectly general, this could lead to a lot of repetition if the
same HIR nodes affect many work-products. This is set to be a problem
when we start to skip typeck, since we will be adding a lot more
"work-product"-like nodes.

The newer code uses an alternative strategy: it "reduces" the graph
instead. Basically we walk the dep-graph and convert it to a DAG, where
we only keep intermediate nodes if they are used by multiple
work-products.

This DAG does not contain the same set of nodes as the original graph,
but it is guaranteed that (a) every output node is included in the graph
and (b) the set of input nodes that can reach each output node is
unchanged.

(Input nodes are basically HIR nodes and foreign metadata; output nodes
are nodes that have assocaited state which we will persist to disk in
some way. These are assumed to be disjoint sets.)

This removes the expand_derives function, and sprinkles
the functionality throughout the Invocation Collector,
Expander and Resolver.

fixes rust-lang/rls#160

…igured

We should be sure to add our build system entry point!

Closes #39476

The old algorithm was O(graph)

I already checked this into stable, but it needs to be on master/beta too.

rewrite the predecessors code to create a reduced graph

The old code created a flat listing of "HIR -> WorkProduct" edges.
While perfectly general, this could lead to a lot of repetition if the
same HIR nodes affect many work-products. This is set to be a problem
when we start to skip typeck, since we will be adding a lot more
"work-product"-like nodes.

The newer code uses an alternative strategy: it "reduces" the graph
instead. Basically we walk the dep-graph and convert it to a DAG, where
we only keep intermediate nodes if they are used by multiple
work-products.

This DAG does not contain the same set of nodes as the original graph,
but it is guaranteed that (a) every output node is included in the graph
and (b) the set of input nodes that can reach each output node is
unchanged.

(Input nodes are basically HIR nodes and foreign metadata; output nodes
are nodes that have assocaited state which we will persist to disk in
some way. These are assumed to be disjoint sets.)

r? @michaelwoerister

Fixes #39494

Expand derive macros in the MacroExpander

This removes the expand_derives function, and sprinkles the functionality throughout the Invocation Collector, Expander and Resolver.

r? @jseyfried

…atsakis

Don't suggest to use things which weren't found either

Fixes #38054

The best code I can come up with, suggestions are welcome.

Basically, removing ```. Did you mean to use `DoesntExist1`?``` in the code below, because it is useless.

```rust
error[E0432]: unresolved import `DoesntExist1`
 --> src/lib.rs:1:5
  |
1 | use DoesntExist1;
  |     ^^^^^^^^^^^^ no `DoesntExist1` in the root

error[E0432]: unresolved import `DoesntExist2`
 --> src/lib.rs:2:5
  |
2 | use DoesntExist2;
  |     ^^^^^^^^^^^^ no `DoesntExist2` in the root. Did you mean to use `DoesntExist1`?
```

save-analysis: be more paranoid about generated paths

fixes rust-lang/rls#160

…ried

Change tracking issue for `proc_macro` feature to #38356

r? @jseyfried

Fix bootstrap.py issues with new rustbuild build system (fixes #39469)

rustbuild: Add x.py to source tarballs

We should be sure to add our build system entry point!

Closes #39476

…ichton

Tiny doc wording change

Fix #39366

Add missing urls in HashMap

r? @frewsxcv

Update relnotes for 1.15.1

I already checked this into stable, but it needs to be on master/beta too.

Rollup of 10 pull requests

- Successful merges: #39424, #39442, #39443, #39453, #39454, #39471, #39478, #39486, #39506, #39517
- Failed merges: #39444