Mark more locals as moved to avoid building drops for them.

[cjgillot]

MIR building skips generating drops for moved-from locals in the topmost scope. This was only used for call terminators, but can be generalized to many other moves. This PR generalizes this to aggregate construction and many other assignments.

This avoids generating drops that would then be removed by drop elaboration.

This PR changes borrowck behaviour: some programs that were rejected are now accepted, see the last commit. That particular case was wrongly rejected.

Fixes #156713

Based on #158279 to remove a lint false-positive

[rustbot]

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[rustbot]

r? @JohnTitor

rustbot has assigned @JohnTitor.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

• Owners of files modified in this PR: compiler
• compiler expanded to 73 candidates
• Random selection from 21 candidates

[theemathas]

Does this have user-visible behavior changes? e.g., see #156713

[cjgillot]

Yes. With this change, both cases in #156713 pass. We also have a few user-visible consequences with the drop order lint.

[JohnTitor]

@rustbot reroll

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[rust-log-analyzer]

The job tidy failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

[TIMING:end] tool::ToolBuild { build_compiler: Compiler { stage: 0, host: x86_64-unknown-linux-gnu, forced_compiler: false }, target: x86_64-unknown-linux-gnu, tool: "tidy", path: "src/tools/tidy", mode: ToolBootstrap, source_type: InTree, extra_features: [], allow_features: "", cargo_args: [], artifact_kind: Binary } -- 58.288
[TIMING:end] tool::Tidy { compiler: Compiler { stage: 0, host: x86_64-unknown-linux-gnu, forced_compiler: false }, target: x86_64-unknown-linux-gnu } -- 0.000
fmt check
Diff in /checkout/tests/mir-opt/coroutine/unwind_in_vec.rs:6:
 // EMIT_MIR unwind_in_vec.build-{closure#0}.ElaborateDrops.diff
 #[inline(never)]
 pub async fn build(s: u64) -> Vec<String> {
-    vec![
-        "0".to_string(),
-        "1".to_string(),
-        "2".to_string(),
-        "3".to_string(),
-        "4".to_string(),
-    ]
+    vec!["0".to_string(), "1".to_string(), "2".to_string(), "3".to_string(), "4".to_string()]
 }
 
fmt: checked 6982 files
Bootstrap failed while executing `test src/tools/tidy tidyselftest --extra-checks=py,cpp,js,spellcheck`
Build completed unsuccessfully in 0:01:36