explain a good reason for why LocalValue does not store the type of the local

[RalfJung]

As found out by @lcnr in #112307, storing the type here can lead to subtle bugs when it gets out of sync with the MIR body. That's not the reason why the interpreter does it this way I think, but good thing we dodged that bullet. :)

[rustbot]

r? @WaffleLapkin

(rustbot has picked a reviewer for you, use r? to override)

[rustbot]

Some changes occurred to the CTFE / Miri engine

cc @rust-lang/miri

[WaffleLapkin]

r=me with green CI

[RalfJung]

@bors r=WaffleLapkin

[bors]

📌 Commit a1b03e3 has been approved by WaffleLapkin

It is now in the queue for this repository.

[RalfJung]

@bors rollup

[bors]

⌛ Testing commit a1b03e3 with merge a1c65db...

[bors]

☀️ Test successful - checks-actions
Approved by: WaffleLapkin
Pushing a1c65db to master...

[rust-timer]

Finished benchmarking commit (a1c65db): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.6%	[-3.9%, -1.9%]	4
All ❌✅ (primary)	-	-	0

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 673.487s -> 671.079s (-0.36%)
Artifact size: 313.39 MiB -> 313.33 MiB (-0.02%)