perf(assertions-analyzers): cache assertion symbols and cut per-call work

[thomhurst]

Summary

Performance cleanup of TUnit.Assertions.Analyzers, following the approach #6917 took for TUnit.Analyzers. Every Assert.That is inspected by several analyzers, and each one was rebuilding display strings or calling GetTypeByMetadataName on every call. They now share a per-compilation symbol cache and compare symbols. The TUnit.Assertions.Analyzers total on TUnit.TestProject drops from about 0.16s to 0.06s, and MixAndOrOperatorsAnalyzer is about 20x faster.

What changed

• Helpers/AssertionSymbols: a new per-compilation cache (ConditionalWeakTable) holding Assert, ShouldExtensions, IAssertionSource(<T>), IShouldSource(<T>) and Assertion<T>, with IsAssertThat / IsShould helpers. Analyzers resolve these in RegisterCompilationStartAction and don't register at all when TUnit.Assertions isn't referenced.
• AwaitAssertionAnalyzer, AwaitValueTaskAssertThatAnalyzer, ConstantInAssertThatAnalyzer, DynamicInAssertThatAnalyzer: these compare symbols instead of building fully qualified name strings. ValueTask/ValueTask<T> and TUnit.Assertions.Assert are resolved once per compilation instead of on every That call.
• MixAndOrOperatorsAnalyzer (runs on every await):
  • It used to call awaitOperation.Descendants().OfType<IPropertyReferenceOperation>().ToArray(). It now walks only the awaited chain's receivers: instance or extension this argument, conversions and parentheses. The walk stops at Should().
  • The expensive awaited-type check (AllInterfaces on constructed generic assertion types) now runs only when the chain contains both And and Or.
• IsNotNullAssertionSuppressor:
  • Diagnostics are grouped by their containing scope. Each scope's IsNotNull()/NotBeNull() candidates are collected once per ReportSuppressions call, and each candidate's semantic validation is memoized. Before, every diagnostic re-walked the whole method and re-validated every candidate.
  • The three GetTypeByMetadataName lookups are resolved once per call.
  • The containing-type string comparisons use the existing IsGloballyQualifiedNonGeneric name prefilter.
  • Matching logic is unchanged, including the rejection of source-defined lookalikes.
• XUnitAssertionAnalyzer: registration is skipped when no Xunit.Assert type exists. The check is a merged global-namespace lookup, so ambiguous references don't disable it.
• CompilerArgumentsPopulatedAnalyzer:
  • It now registers on Invocation + ObjectCreation instead of Argument, the most frequent operation kind, so calls outside TUnit.Assertions are rejected once per call rather than once per argument.
  • Caller-info parameters are cached per method definition.

Not done: the shared GloballyQualified name matcher (TypeExtensions.GloballyQualified.cs) still re-parses its expected string on every call. After these changes it's no longer hot in this assembly: its remaining callers are cached per method, per suppression candidate, or run only on Equals calls. It's also shared with TUnit.Analyzers, so I left it alone.

Deliberate behavior changes

1. TUnitAssertions0001 (mixed And/Or) no longer counts And/Or from separate assertion chains nested in arguments or lambdas.
   • Before, await Assert.ThrowsAsync(async () => { await Assert.That(1).IsEqualTo(2).Or.IsEqualTo(3); await Assert.That(2).IsEqualTo(3).And.IsEqualTo(4); }) was flagged even though no single chain mixes the two. That's the one diagnostic that disappears from tests/TUnit.Assertions.Tests (Old/AssertMultipleTests.cs:70).
   • A nested chain that does mix is now reported once, on its own await, instead of on both the inner and outer await.
   • Ternaries inside the awaited expression are no longer walked. That's an edge case: the two branches aren't one chain.
2. TUnitAssertions0003 (caller-info argument populated) now checks the target method's assembly. The old code checked argument.Parent.Type.ContainingAssembly, which is the invocation's return type assembly, and that looks like a bug. What changed:
   • It now flags TUnit.Assertions methods whose return type is outside TUnit.Assertions. Reflecting over the shipped assembly finds only Assert.NotNull(value, "expr") and Assert.Null(value, "expr") (both return void), plus the generic-returning CollectionItemSatisfiesExtensions.Satisfies.
   • It no longer flags user-defined methods that happen to return a TUnit.Assertions type (e.g. a custom MyThat(...) wrapper returning ValueAssertion<T>). A wrapper's forwarding call into Assert.That(value, expression) is still flagged, as before.
   • TUnit.Assertions.Should isn't affected either way: all 231 of its caller-info methods return Should types.

New tests cover each change: 4 of the 5 added tests fail against the old analyzers. The fifth covers parenthesized chains and passes on both.

Measurements

Every run is a warm compiler server (restarted and warmed up after each analyzer DLL swap), dotnet build -f net10.0 -c Release --no-dependencies -p:ReportAnalyzer=true -v:d. Values are the TUnit.Assertions.Analyzers rows. Old and new DLLs were swapped and interleaved over 2 rounds; the table shows medians. The machine was noisy (other builds running), so individual runs vary by roughly 2x.

TUnit.Assertions.Analyzers total

Project	Before	After
tests/TUnit.TestProject (12 runs each)	0.156s	0.062s
Synthetic: 100 classes, ~5,500 Assert.That, 1,500 suppressed CS8602 (6 runs each)	0.285s	0.192s

Per analyzer, synthetic project

Analyzer	Before	After
MixAndOrOperatorsAnalyzer	0.094s	0.006s
AwaitValueTaskAssertThatAnalyzer	0.062s	0.022s
AwaitAssertionAnalyzer	0.019s	0.012s
IsNotNullAssertionSuppressor	0.097s	0.084s (within noise)

I also used an isolated in-process harness: CompilationWithAnalyzers, non-concurrent, the same synthetic sources with the TUnit source generator applied, one analyzer at a time. There, MixAndOrOperatorsAnalyzer went from about 379ms to 8ms. A no-op await analyzer showed that most of the remaining pre-change cost was AllInterfaces on the awaited type, which is why that check now runs last.

On the synthetic project, the suppressor gain is within noise because each method there has only a few diagnostics. The change removes the O(diagnostics × scope size) re-scan and the repeated semantic validation for methods with many nullable warnings.

Testing done

• tests/TUnit.Assertions.Analyzers.Tests: 117/117 pass on net10.0 and net8.0. That includes 5 new tests (3 MixAndOr, 2 CompilerArgumentsPopulated).
• tests/TUnit.Assertions.Analyzers.CodeFixers.Tests: 19/19 pass on net10.0. That includes the xUnit code-fix tests, which reference the real xunit package, so they exercise the new registration gate.
• Diagnostic equivalence: I built TUnit.TestProject, TUnit.Assertions.Tests and the synthetic project with the old and new analyzers and SARIF error logs, then compared every result, suppressed ones included, by rule, location and suppression.
  • TUnit.TestProject (3,335 results) and the synthetic project (2,652 results, including 1,500 IsNotNullAssertionSuppressor suppressions) are identical.
  • TUnit.Assertions.Tests differs only by the one TUnitAssertions0001 false positive described above.

Summary by CodeRabbit

• Bug Fixes
  • Improved assertion diagnostics for caller-info arguments and mixed .And/.Or chains, including nested and parenthesized assertions.
  • Improved recognition of TUnit and xUnit assertions referenced through aliases, reducing missed or incorrectly matched diagnostics.
  • Refined detection of unawaited assertions, constant or dynamic assertion arguments, and assertion-related null-check suppressions.
• Tests
  • Added coverage for aliased assertion references, forwarded arguments, and nested or parenthesized assertion chains.

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📝 Walkthrough

Walkthrough

The pull request updates assertion analyzers to resolve symbols across compilation references. It revises caller-info argument analysis, null-check suppression, and mixed And/Or chain detection. Tests cover extern aliases, caller-info arguments, and nested assertion chains.

Changes

Analyzer updates

Layer / File(s)	Summary
Assertion symbol resolution and analyzer registration src/TUnit.Assertions.Analyzers/Helpers/TypeSymbolSet.cs, src/TUnit.Assertions.Analyzers/Helpers/AssertionSymbols.cs, src/TUnit.Assertions.Analyzers/AwaitAssertionAnalyzer.cs, src/TUnit.Assertions.Analyzers/AwaitValueTaskAssertThatAnalyzer.cs, src/TUnit.Assertions.Analyzers/ConstantInAssertThatAnalyzer.cs, src/TUnit.Assertions.Analyzers/DynamicInAssertThatAnalyzer.cs, src/TUnit.Assertions.Analyzers/XUnitAssertionAnalyzer.cs, tests/TUnit.Assertions.Analyzers.Tests/AwaitAssertionAnalyzerTests.cs, tests/TUnit.Assertions.Analyzers.Tests/XUnitAssertionAnalyzerTests.cs, tests/TUnit.Assertions.Analyzers.Tests/Verifiers/CSharpAnalyzerVerifier\1.cs`	Analyzers resolve assertion and framework types during compilation analysis. Symbol checks identify assertion methods across global and extern-aliased references. Tests exercise TUnit and XUnit assertions with aliased references.
Caller-info argument diagnostics src/TUnit.Assertions.Analyzers/CompilerArgumentsPopulatedAnalyzer.cs, tests/TUnit.Assertions.Analyzers.Tests/CompilerArgumentsPopulatedAnalyzerTests.cs, tests/TUnit.Assertions.Analyzers.Tests/Verifiers/CSharpAnalyzerVerifier\1.cs`	The analyzer checks explicit arguments to methods in resolved TUnit assertion assemblies and caches caller-info parameter flags. Tests cover populated arguments, forwarded wrapper arguments, constructors, and aliased references.
Null-check suppression candidate analysis src/TUnit.Assertions.Analyzers/IsNotNullAssertionSuppressor.cs	The suppressor caches null-check candidates by scope and resolves relevant types per analysis call. It filters candidates by statement position and compares asserted expressions with warning targets.
Mixed And/Or assertion-chain analysis src/TUnit.Assertions.Analyzers/MixAndOrOperatorsAnalyzer.cs, tests/TUnit.Assertions.Analyzers.Tests/MixAndOrOperatorsAnalyzerTests.cs	The analyzer walks awaited receiver chains to detect mixed And and Or operators. Tests cover parenthesized chains and nested assertions.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~45 minutes

Change: Refactor

Merge Risk: ⚪ Minimal · up to 62822

The analyzer changes are mergeable after normal checks; no actionable issue remains identified.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 66c87

The change may cause a caller-info diagnostic to apply to methods outside the intended assertion library when another assembly defines the same assertion type name. The identified effect is limited to build diagnostics; no runtime access or privilege change was established. Security coverage remains incomplete.

Retained concerns

• Low · architecture · inferred: An assembly that defines a type named TUnit.Assertions.Assert can qualify all of its methods for caller-info argument diagnostics, including methods unrelated to assertions. The previous assembly-name gate did not admit those other assemblies.

Security review details

Security Blast Radius

• inferred — Compilation inputs can influence which assembly symbols qualify for diagnostics. The inspected paths produce compiler diagnostics or suppressions; no tenant, credential, network, or runtime privilege transition was established.

Trust Boundaries and Controls

• observed — Most inspected assertion-call recognition compares Roslyn symbol identities, while the caller-info analyzer uses membership of the method's entire containing assembly. The null-warning suppressor applies an additional TUnit assembly check.

Hardening Proposals

• proposed — Constrain caller-info diagnostic eligibility to the intended assertion assembly identity or assertion methods, rather than treating the presence of one matching type as authority for every method in its assembly.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 21.21% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 66 functions across 15 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main performance changes: caching assertion symbols and reducing per-call analyzer work.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[github-actions]

Review

I read the shared AssertionSymbols cache and the rewritten MixAndOrOperatorsAnalyzer in full. I skimmed the other analyzers in the diff but did not build the project or run any tests, so my comments below are from reading the code only.

What looks good

• The per-compilation ConditionalWeakTable cache is a sound design. It lets the analyzers do symbol comparisons instead of string building, and they skip registration when TUnit.Assertions isn't referenced.
• The MixAndOr receiver walk is much cheaper than Descendants().OfType().ToArray(). Deferring the AllInterfaces check until both And and Or are present is a good change.
• The null checks are handled correctly. SymbolEqualityComparer.Equals(x, null) returns false, so the nullable symbols are safe.

Points to consider

1. Behavior change in MixAndOrOperatorsAnalyzer. The old code scanned all descendants. The new walk follows only the receiver chain. That is arguably more correct, because a nested assertion in an argument is its own chain. But a chain that used to be flagged through an argument, or through an operation kind the default branch doesn't handle, is now silently missed. Examples are a null-forgiving or as cast, which show up as a conversion or a different operation, and a ConditionalAccess operation. I'd add analyzer tests for these:
   • (await ...) with parentheses
   • a chain through a conversion
   • And and Or inside a lambda argument, asserting the intended non-report
2. GetTypeByMetadataName returns null when the type is ambiguous. If two referenced assemblies define the same type, for example via an internal copy, the analyzers silently turn off. That is unlikely and the trade-off is acceptable. A short comment in AssertionSymbols would make it explicit.
3. Minor. IsAssertionSource checks four symbols per interface. If the awaited type has many interfaces, a HashSet or an early check on @interface.ContainingNamespace would be cheaper. This is now off the hot path, so it isn't worth doing.

Overall this is a clean, well-motivated perf cleanup. I'd like to see the extra test coverage from point 1 before merging, but I don't see a blocker.

[greptile-apps]

Confidence Score: 5/5

[Medium risk] Refactors assertion analyzers to cache symbol lookups.

The PR appears safe to merge; no outstanding or new actionable findings remain.

Summary

The PR caches assertion symbols per compilation and reduces repeated work across assertion analyzers. It also narrows mixed-chain analysis, updates caller-info argument checks, and adds alias and constructor coverage.

• The three previous alias-related findings are addressed in the current code.
• No new actionable issue was identified in the changes since the previous review.

_{Reviews (4) · Last reviewed commit: "test(assertions-analyzers): cover constr..."}

[github-actions]

Review: PR 6927 (TUnit.Assertions.Analyzers perf cleanup)

I read the full diff and found nothing blocking. I did not build the branch or run the tests, and the code-review skill failed to run, so this is a manual read.

What looks good

• AssertionSymbols is a sound design. A ConditionalWeakTable keyed on the compilation resolves each symbol once. Analyzers skip registration when TUnit.Assertions isn't referenced, and symbol comparison replaces string building on the hot path.
• The extern-alias fallback in ResolveType is well reasoned and has a regression test.
• MixAndOrOperatorsAnalyzer now walks only the receiver chain and defers the AllInterfaces check until both And and Or are found. That is a real algorithmic improvement over Descendants().OfType().ToArray().
  • It also fixes false positives from nested assertions inside lambdas or arguments. The new tests cover this.
• CompilerArgumentsPopulatedAnalyzer registers on invocations and object creations, and the caller-info flags are cached per OriginalDefinition in a ConcurrentDictionary. Filtering by the target method's assembly is more accurate than the old check on the parent's return type.
• IsNotNullAssertionSuppressor groups candidates by scope and memoizes each candidate's semantic validation.

Minor observations (non-blocking)

1. ResolveType returns the first referenced assembly that defines the type. If two aliased copies of TUnit.Assertions are referenced, only one is matched. That is an unusual setup, but a short comment would make the limitation explicit.
2. NullCheckTypes and NullCheckCandidate use non-thread-safe lazy state. This is fine because ReportSuppressions runs single-threaded per call and they are locals. A comment saying so would protect against future sharing.
3. AssertionSymbols exposes ResolveType publicly, and the suppressor and XUnitAssertionAnalyzer both use it. It could move into a neutral helper, though that is not needed.
4. MixAndOrOperatorsAnalyzer.GetReceiver handles instance calls and extension this arguments only. That matches how assertion chains are built today. If a new chain shape appears (for example a static helper wrapper), it would silently stop the walk and miss the diagnostic. The tests are a decent safety net.

Overall this is a clean, well-tested change. The added tests cover extern alias, parenthesized chains, nested assertions and user wrappers. Approving from my side.

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⚠️ Outside diff range comments (1)

🟡 Minor · Track all matching assertion assemblies in this… · CompilerArgumentsPopulatedAnalyzer.cs:24-50

src/TUnit.Assertions.Analyzers/CompilerArgumentsPopulatedAnalyzer.cs:24-50
🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Track all matching assertion assemblies in this analyzer.

AssertionSymbols.ResolveType returns one Assert symbol. Its fallback returns the first matching referenced assembly. This analyzer compares each method against that single assembly.

When a compilation references global and aliased TUnit.Assertions assemblies, an explicit argument to a caller-info parameter on a method from the other assembly fails the comparison. The analyzer then omits TUnitAssertions0003. Preserve the existing non-TUnit filter, but match every assembly that defines the assertion API and add a regression test for two references.

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Review comment at
@src/TUnit.Assertions.Analyzers/CompilerArgumentsPopulatedAnalyzer.cs around
lines 24 - 50:
Update CompilerArgumentsPopulatedAnalyzer’s assembly matching so
AnalyzeArguments recognizes methods from every assembly defining the assertion
API, rather than only the single assembly returned by AssertionSymbols.For;
preserve the existing non-TUnit filter. Add a regression test with global and
aliased TUnit.Assertions references that verifies explicit caller-info arguments
on methods from both assemblies report TUnitAssertions0003.

---

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🤖 Prompt to fix review comments

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Inline comments:
Review comments at @src/TUnit.Assertions.Analyzers/Helpers/AssertionSymbols.cs:
- Around line 62-66: Update ResolveType in AssertionSymbols and the cached
assertion-type comparisons so they recognize every referenced symbol matching
the metadata name, rather than returning only the first match. Ensure
IsAssertThat, IsShould, and the other assertion checks correctly match methods
bound through extern aliases.

---

Outside diff comments:
Review comments at
@src/TUnit.Assertions.Analyzers/CompilerArgumentsPopulatedAnalyzer.cs:
- Around line 24-50: Update CompilerArgumentsPopulatedAnalyzer’s assembly
matching so AnalyzeArguments recognizes methods from every assembly defining the
assertion API, rather than only the single assembly returned by
AssertionSymbols.For; preserve the existing non-TUnit filter. Add a regression
test with global and aliased TUnit.Assertions references that verifies explicit
caller-info arguments on methods from both assemblies report
TUnitAssertions0003.

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• src/TUnit.Assertions.Analyzers/Helpers/AssertionSymbols.cs
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• src/TUnit.Assertions.Analyzers/XUnitAssertionAnalyzer.cs
• tests/TUnit.Assertions.Analyzers.Tests/AwaitAssertionAnalyzerTests.cs
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[thomhurst]

@coderabbitai Re the outside-diff finding on CompilerArgumentsPopulatedAnalyzer.cs (single assertion assembly): confirmed and fixed in 66c8792. The analyzer now holds the TypeSymbolSet for TUnit.Assertions.Assert and accepts a method when its containing assembly is any assembly that defines that type. Methods from other assemblies are still rejected as before. Regression tests: CompilerArgumentsPopulatedAnalyzerTests.Flagged_For_Global_And_Extern_Aliased_Assertion_Assemblies (fails on the previous commit) and Not_Flagged_For_Extern_Aliased_Copy_When_Not_Populated.

[github-actions]

Review of #6927

I reviewed the diff by reading it, and I did not build the analyzers or run the tests. The code-review skill failed to run, so this is a manual review.

The approach is sound. It resolves symbols once per compilation and compares them instead of building display strings. The MixAndOr receiver walk and the memoized scope candidates in IsNotNullAssertionSuppressor follow from that.

Things I checked and found fine:

• Extern aliases: TypeSymbolSet handles extern-aliased copies of TUnit.Assertions, which GetTypeByMetadataName alone would miss. It only takes the slow path when a non-global alias exists.
• Early exit: analyzers skip registration entirely when TUnit.Assertions isn't referenced.
• Cache lifetime: ConditionalWeakTable keyed by Compilation doesn't leak. The per-compilation ConcurrentDictionary in CompilerArgumentsPopulatedAnalyzer is thread-safe.

Suggestions, none of them blocking:

1. Behaviour change in CompilerArgumentsPopulatedAnalyzer. It used to fire for any IArgumentOperation whose parent's result type was in TUnit.Assertions. That check tested the wrong thing (the return type), so testing the method's assembly is more correct. It now only covers invocations and object creations. Arguments to indexers or attribute constructors are no longer visited, though those have no caller-info parameters in practice. A test that pins this down would help, for example a [CallerArgumentExpression] argument on a constructor of an assertion type, plus the extern-alias case.
2. Duplicated resolution. AwaitValueTaskAssertThatAnalyzer still resolves ValueTask and ValueTask1by itself. If more analyzers need BCL types, put them inAssertionSymbols` (or a sibling cache) so there is one pattern.
3. Caller-info flags. GetCallerInfoFlags allocates a bool[] per method definition. That is acceptable because it is cached, but a ulong bitmask would avoid the array for methods with 64 or fewer parameters. This is minor.
4. TypeSymbolSet as a struct. It holds two references, so it is a 16-byte struct copied on every property access. That is fine, but readonly members and in parameters would make the intent clearer. This is a nit.

The change is good overall. The measured drop from about 0.16s to 0.06s and the roughly 20x speedup on MixAndOrOperatorsAnalyzer justify it. Please confirm the analyzer test suite is green, including the extern-alias tests.

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🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
set -euo pipefail
fd -t f '^(CompilerArgumentsPopulatedAnalyzer|CompilerArgumentsPopulatedAnalyzerTests|TypeSymbolSet)\.cs$'
ast-grep outline src/TUnit.Assertions.Analyzers/CompilerArgumentsPopulatedAnalyzer.cs --items all
ast-grep outline tests/TUnit.Assertions.Analyzers.Tests/CompilerArgumentsPopulatedAnalyzerTests.cs --items all --match 'Flagged_For_Global_And_Extern_Aliased_Assertion_Assemblies|Not_Flagged_For_Extern_Aliased_Copy_When_Not_Populated'
sed -n '1,240p' src/TUnit.Assertions.Analyzers/CompilerArgumentsPopulatedAnalyzer.cs
rg -n -A45 -B8 'Flagged_For_Global_And_Extern_Aliased_Assertion_Assemblies|Not_Flagged_For_Extern_Aliased_Copy_When_Not_Populated' tests/TUnit.Assertions.Analyzers.Tests/CompilerArgumentsPopulatedAnalyzerTests.cs

Length of output: 8753

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🏁 Script executed:

#!/bin/bash
set -euo pipefail
ast-grep outline src/TUnit.Assertions.Analyzers/Helpers/TypeSymbolSet.cs --items all --match 'ContainsAssembly|Resolve'
sed -n '1,235p' src/TUnit.Assertions.Analyzers/Helpers/TypeSymbolSet.cs

Length of output: 5608

---

@thomhurst, thanks for the fix and the regression tests. I checked CompilerArgumentsPopulatedAnalyzer.cs: it now accepts methods from every assembly in the resolved TUnit.Assertions.Assert type set and rejects methods from other assemblies. The two named regression tests cover the populated and unpopulated cases. I did not run the tests in this inspection environment.

---

✏️ Learnings added

Learnt from: thomhurst
URL: https://github.com/thomhurst/TUnit/pull/6927

Timestamp: 2026-09-29T10:17:02.576Z
Learning: In `src/TUnit.Assertions.Analyzers/CompilerArgumentsPopulatedAnalyzer.cs`, the C# analyzer accepts a method for caller-info argument diagnostics when the method's containing assembly is any assembly that defines `TUnit.Assertions.Assert`, including an extern-aliased copy. It rejects methods from other assemblies.

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[thomhurst]

Thanks for the review. Responses to the four points:

1. CompilerArgumentsPopulatedAnalyzer scope: Added tests in 6282230. They cover new ExpressionCapture(1, "explicit"), target-typed new(1, expression: ..., member: ...), and a : base(value, "...") constructor initializer. Each call targets a type in an extern-aliased assembly that defines TUnit.Assertions.Assert, and the constructor has [CallerArgumentExpression] and [CallerMemberName] parameters. Explicit arguments are flagged and omitted ones are not. As a check, I disabled the object-creation registration and the new "flagged" test failed. Existing tests already cover extern-aliased Assert.That invocations. On the other shapes you raised:

   • Attribute constructors: these are irrelevant. Their arguments are AttributeArgumentSyntax, not ArgumentSyntax, so the previous implementation skipped them too.
   • Indexers: the only indexers in TUnit.Assertions are this[int index], and they have no caller-info parameters.
   • Constructor initializers: these are IInvocationOperations, so they are covered.

   The remaining behaviour changes are intentional and already tested. A user method that returns an assertion type is no longer checked (User_Method_Returning_TUnit_Assertion_Is_Not_Flagged). Void-returning assertion methods such as Assert.NotNull are now checked, where before they were missed (Expression_Argument_Is_Flagged_For_TUnit_Assertions_Method_Returning_Void).

2. ValueTask in AssertionSymbols: Not changed. ValueTask and ValueTask<T> are already resolved once per compilation at compilation start, not per call, so moving them saves nothing. AssertionSymbols holds the TUnit types that need multi-assembly/extern-alias matching through TypeSymbolSet. The BCL types don't need that, and only this one analyzer uses them, so I'd rather keep them local.

3. bool[] vs ulong bitmask in GetCallerInfoFlags: Not changed. The array is allocated once per distinct method definition per compilation and then cached, so it isn't a per-call cost. A bitmask would also need a fallback path for methods with more than 64 parameters. The extra code isn't worth it for an allocation this rare.

4. TypeSymbolSet readonly: Already done. It is declared as internal readonly struct TypeSymbolSet with readonly fields.

TUnit.Assertions.Analyzers.Tests passes on net8.0, net9.0 and net10.0 (126/126 each).

[github-actions]

Review: analyzer perf cleanup

I read the diff and didn't build it or run the tests. I found no blocking issues.

What looks good

• AssertionSymbols and TypeSymbolSet resolve the symbols once per compilation. They also handle extern-aliased copies of TUnit.Assertions, which a plain GetTypeByMetadataName misses.
• Analyzers no longer register when TUnit.Assertions isn't referenced.
• Comparing symbols is more robust than comparing display strings.
• The suppressor now collects candidates once per scope, and the GetSemanticModel call is deferred.

Minor points

• CompilerArgumentsPopulatedAnalyzer now registers on Invocation and ObjectCreation only. The old OperationKind.Argument registration also covered other operations that take arguments, such as indexer or property references and : this(...) initializers. TUnit.Assertions probably has no caller-info parameters in those positions. If that's right, this is fine. A regression test with an explicit argument passed to a caller-info parameter through a constructor would pin it down.
• The old check used the assembly name TUnit.Assertions. The new check uses assemblies that define Assert. This is stricter, and it's correct for aliased copies.
• ConditionalWeakTable keyed on Compilation is fine. The cached symbols hold the compilation alive only as long as the key, and the table handles that.

Nice work overall.