Perf Phase 1: syntactic prefilters before semantic-model calls

[credfeto]

Part of #455. Depends on the benchmark baseline from the Phase 0 sub-issue.

Classic analyzer perf bug: calling GetSymbolInfo/GetTypeInfo/GetDeclaredSymbol before cheap syntactic checks (node kind, Identifier.Text, modifiers). Fix by adding a cheap syntactic prefilter before each semantic-model call. Ordered by impact:

• ProhibitedMethodsDiagnosticsAnalyzer.cs:281-287 — GetTypeInfo runs on every member access before any name check. Add a static HashSet<string> of banned member names (Now, UtcNow, Today, Parse, InvariantCulture, …) tested against Name.Identifier.Text first. Biggest single win in the package.
• ForceMethodParametersInvocationsDiagnosticsAnalyzer.cs:137 — method-name text prefilter (Serialize, SerializeAsync, Deserialize, DeserializeAsync, Received) before FindInvokedMemberSymbol
• ProhibitedMethodInvocationsDiagnosticsAnalyzer.cs:154 — prefilter on {True, False, AddOrUpdate, GetOrAdd, Equals} before FindInvokedMemberSymbol
• ProhibitedMethodWithStrictParametersInvocationDiagnosticsAnalyzer.cs:110 — prefilter on {Received, AddJsonFile} before FindInvokedMemberSymbol
• ProhibitedClassesInTestAssembliesDiagnosticsAnalyzer.cs:141 — syntactic prefilter for Console receivers
• ProhibitedSubstituteForUsageInTestBaseDiagnosticsAnalyzer.cs:187 — check syntactic name text is For before GetSymbolInfo
• ArgumentExceptionAnalysisDiagnosticsAnalyzer.cs:73 — check objectCreation.Type identifier text against {ArgumentException, ArgumentNullException, ArgumentOutOfRangeException} before GetSymbolInfo
• TestClassFieldsAnalysisDiagnosticsAnalyzer.cs:38 — reorder: cheap readonly/const modifier check BEFORE the semantic IsDerivedFromTestBase walk
• TestClassPropertyAnalysisDiagnosticsAnalyzer.cs:42 — reorder: syntactic accessor-mutability check BEFORE IsDerivedFromTestBase
• TestClassAnalysisDiagnosticsAnalyzer.cs:59 — syntactic attribute-name prefilter ({Fact, Theory, FactAttribute, TheoryAttribute}) before per-attribute GetTypeInfo, and/or gate the analyzer on IsTestAssembly() at compilation start

Verification: full test suite green, benchmarks from the Phase 0 sub-issue show reduced mean time / allocations for affected analyzers, no change in the set of diagnostics produced.

[dnyw4l3n13]

Implementation Plan

Files to change

• `src/FunFair.CodeAnalysis/ProhibitedMethodsDiagnosticsAnalyzer.cs` — add a static `HashSet` of all banned member names derived from `BannedMethods`, then in `LookForBannedMethods` check `memberAccessExpressionSyntax.Name.Identifier.Text` against it before calling `ExtractTypeInfo`/`GetTypeInfo`
• `src/FunFair.CodeAnalysis/ForceMethodParametersInvocationsDiagnosticsAnalyzer.cs` — extract the method name syntactically from the invocation expression (via `MemberAccessExpressionSyntax.Name.Identifier.Text` or `SimpleNameSyntax.Identifier.Text`) and check against a precomputed `HashSet` of `{Serialize, SerializeAsync, Deserialize, DeserializeAsync, Received}` before calling `FindInvokedMemberSymbol`
• `src/FunFair.CodeAnalysis/ProhibitedMethodInvocationsDiagnosticsAnalyzer.cs` — same pattern: syntactic name prefilter against `{True, False, AddOrUpdate, GetOrAdd, Equals}` before `FindInvokedMemberSymbol`
• `src/FunFair.CodeAnalysis/ProhibitedMethodWithStrictParametersInvocationDiagnosticsAnalyzer.cs` — same pattern: syntactic name prefilter against `{Received, AddJsonFile}` before `FindInvokedMemberSymbol`
• `src/FunFair.CodeAnalysis/ProhibitedClassesInTestAssembliesDiagnosticsAnalyzer.cs` — add syntactic receiver-name prefilter (check if the receiver identifier text is `Console`) before calling `FindInvokedMemberSymbol`
• `src/FunFair.CodeAnalysis/ProhibitedSubstituteForUsageInTestBaseDiagnosticsAnalyzer.cs` — in `GetSubstituteForMethodSymbol`, check that the expression's name identifier text is `For` before calling `GetSymbolInfo`
• `src/FunFair.CodeAnalysis/ArgumentExceptionAnalysisDiagnosticsAnalyzer.cs` — in `ArgumentExceptionsMustPassParameterName`, check `objectCreation.Type`'s identifier text against `{ArgumentException, ArgumentNullException, ArgumentOutOfRangeException}` before calling `GetSymbolInfo`
• `src/FunFair.CodeAnalysis/TestClassFieldsAnalysisDiagnosticsAnalyzer.cs` — in `FieldMustBeReadOnly`, reorder so that the cheap `readonly`/`const` modifier check (syntactic) happens BEFORE the semantic `IsDerivedFromTestBase` walk
• `src/FunFair.CodeAnalysis/TestClassPropertyAnalysisDiagnosticsAnalyzer.cs` — in `PropertyMustBeReadOnly`, reorder so that the syntactic accessor-mutability check happens BEFORE `IsDerivedFromTestBase`
• `src/FunFair.CodeAnalysis/Helpers/TestDetection.cs` — in `IsTestMethod`, add a syntactic prefilter that skips `GetTypeInfo` for any attribute whose name is not in `{Fact, Theory, FactAttribute, TheoryAttribute}`

Approach

For each affected analyzer, insert a cheap syntactic prefilter immediately after the node-type guard (the existing `is not XSyntax` check), before any semantic-model call (`GetTypeInfo`, `GetSymbolInfo`, `FindInvokedMemberSymbol`). The prefilter uses `Identifier.Text` on the syntax node's name token and compares against a static `HashSet` (or `FrozenSet` if available in the target TFM) populated at class-initialisation time; this is a pure string dictionary lookup with no allocations. For the three `TestClass*` analyzers the fix is a reorder: the syntactic check is already present but is evaluated after the expensive semantic walk — swapping the order avoids the semantic call entirely for fields/properties that are already read-only or properties that have no setter. For `TestDetection.IsTestMethod`, a syntactic attribute-name filter is added so `GetTypeInfo` is only called for attributes whose unqualified name matches a known test attribute name. For `ProhibitedMethodsDiagnosticsAnalyzer`, the set of banned method names is derived from the existing `BannedMethods` array at static initialisation rather than being hardcoded, so it stays in sync automatically as new rules are added.

Test strategy

The existing test suites for all ten analyzers (in `src/FunFair.CodeAnalysis.Tests/`) cover both triggering and non-triggering cases and will be run unmodified to confirm that no diagnostic is added or removed by these purely internal ordering changes. The Phase 0 benchmarks (in `src/FunFair.CodeAnalysis.Benchmark.Tests/`) will be re-run after the changes; the mean time and/or allocation figures for the affected analyzers are expected to decrease relative to the recorded baseline.

Assumptions

• `FrozenSet` (System.Collections.Frozen, .NET 8+) is available in the target TFM; if not, `HashSet` with `StringComparer.Ordinal` is used instead.
• The set of banned names for `ProhibitedMethodsDiagnosticsAnalyzer` is derived programmatically from `BannedMethods` so no manual maintenance is required.
• No new test cases are needed because the prefilter must not change the set of reported diagnostics — the existing tests already assert that invariant.

Open questions

None — ready to proceed pending approval.

[dnyw4l3n13]

Draft PR #463 created at #463 on branch perf/457-syntactic-prefilters-before-semantic-model-calls — implementation of the approved plan will proceed in subsequent cycles via the pull-request workflow.