support duplicate entries in the opaque_type_storage

[lcnr]

Necessary for the new solver as we may unify keys when eagerly resolving for canonical queries. See the relevant comment when instantiating query responses:

            // We eagerly resolve inference variables when computing the query response.
            // This can cause previously distinct opaque type keys to now be structurally equal.
            //
            // To handle this, we store any duplicate entries in a separate list to check them
            // at the end of typeck/borrowck. We could alternatively eagerly equate the hidden
            // types here. However, doing so is difficult as it may result in nested goals and
            // any errors may make it harder to track the control flow for diagnostics.
            if let Some(prev) = prev {
                self.delegate.add_duplicate_opaque_type(key, prev, self.origin_span);
            }

This will be far more relevant with #140497.

r? @compiler-errors

[rustbot]

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

[lcnr]

@bors try @rust-timer queue

[bors]

⌛ Trying commit a714e28 with merge 93308d9...

[bors]

☀️ Try build successful - checks-actions
Build commit: 93308d9 (93308d94b2869be5d252948a335d86db7f041654)

[rust-timer]

Finished benchmarking commit (93308d9): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

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

Max RSS (memory usage)

Results (primary -0.1%)

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)	0.6%	[0.4%, 1.3%]	21
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.6%	[-6.6%, -0.5%]	6
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.1%	[-6.6%, 1.3%]	27

Cycles

Results (primary -0.6%, secondary -1.8%)

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)	0.5%	[0.4%, 0.6%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.7%	[-1.5%, -0.4%]	19
Improvements ✅ (secondary)	-1.8%	[-2.1%, -1.4%]	3
All ❌✅ (primary)	-0.6%	[-1.5%, 0.6%]	22

Binary size

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

Bootstrap: 769.364s -> 769.01s (-0.05%)
Artifact size: 365.54 MiB -> 365.46 MiB (-0.02%)