rustc: use more correct span data in for loop desugaring

[notriddle]

Fixes #82462

Before:

  help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
     |
  LL |     for x in DroppingSlice(&*v).iter(); {
     |                                       +

After:

  help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
     |
  LL |     };
     |      +

This seems like a reasonable fix: since the desugared "expr_drop_temps_mut" contains the entire desugared loop construct, its span should contain the entire loop construct as well.

[rust-highfive]

r? @nagisa

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[nagisa]

On one hand this looks like a nice improvement in that we no longer suggest non-sense, but on the other adding a semicolon there won't help either way (and the message sounds quite confident it would help…)

Please squash. r=me.

[notriddle]

@nagisa okay, it's squashed

[nagisa]

@bors r+

[bors]

📌 Commit 4b3bcb72a81c3bc8519366d071dc9a06e8ef2174 has been approved by nagisa

[bors]

⌛ Testing commit 4b3bcb72a81c3bc8519366d071dc9a06e8ef2174 with merge 0edc41c7315527e739aca1cb018d2459dee61abe...

[bors]

💔 Test failed - checks-actions

[notriddle]

I guess I'll rebase onto the master branch? I'm not actually sure what's wrong here: after locally rebasing and running with --bless, it didn't change the output.

[nagisa]

Did you re-generate the .stderr file after the rebase? Bors will always merge in master when testing a diff and this is the diff from the test output, while the PRd stderr file still contains the larger span.

---- [ui (nll)] ui/borrowck/issue-82462.rs stdout ----
diff of stderr:

7	   |              |               immutable borrow occurs here
8	   |              a temporary with access to the immutable borrow is created here ...
9	LL |         v.push(*x);
-	   |         ^^^^^^^^^^ mutable borrow occurs here
+	   |         ^ mutable borrow occurs here
11	LL |         break;
12	LL |     }
13	   |     - ... and the immutable borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `DroppingSlice`

[notriddle]

Yes, I tried to regenerate it and nothing happened.

[nagisa]

@bors r+

Lets try it again, then.

[bors]

📌 Commit 0b451b8c57fa6fdbe6ef460a1362bf1cfed70d5d has been approved by nagisa

[nagisa]

@bors rollup=never

[notriddle]

Okay, so it's not my local install. Why are optimizations impacting the format of error output?

[nagisa]

Hm, since this error is generated by borrowck, it could be that we inadvertently run some MIR pass before borrowck that we don't run in non-optimized builds? (You could verify with -Zmir-opt-level or whatever the flag is called)

[notriddle]

Found it. It's actually caused by test-compare-mode, and not the optimization stack.

I've added a second stderr file for this.

[nagisa]

@bors r+

[bors]

📌 Commit fe1a7f7 has been approved by nagisa

[bors]

⌛ Testing commit fe1a7f7 with merge f6f0cf7d2042b00d9eb2bf23a3c4b89afd3e7073...

[bors]

💔 Test failed - checks-actions

[notriddle]

@nagisa New commit to fix the broken Clippy lints.

[nagisa]

@bors r+

[bors]

📌 Commit 543e601 has been approved by nagisa

[bors]

🌲 The tree is currently closed for pull requests below priority 100. This pull request will be tested once the tree is reopened.

[bors]

⌛ Testing commit 543e601 with merge 4e880f8...

[bors]

☀️ Test successful - checks-actions
Approved by: nagisa
Pushing 4e880f8 to master...

[rust-timer]

Finished benchmarking commit (4e880f8): comparison url.

Summary: This benchmark run did not return any relevant changes.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression