[teneko]

Stacked on #4 (fix/analyzer-diagnostics). Retarget this PR to main once #4 is merged.

Problem

A type became a matcher implicitly, only because some target listed it in Matchers = [typeof(T)]. The role was decided somewhere else, which caused two problems:

• Generator: IUserService with [GenerateOverloads(nameof(name))] void Update(int id, string? name); gets Update(this IUserService, int). As soon as another class adds [GenerateOverloads(Matchers = [typeof(IUserService)])] to its own method, the IUserService overload disappears (OverloadPlanBuilder skipped every type that was referenced as a matcher anywhere).
• Analyzer (fix: report analyzer diagnostics per type at in-source locations #4): each type is analyzed on its own, so an unreferenced-looking matcher type was treated as a direct target. This produced false generation diagnostics: two MOG006 in the acceptance project (Class_4_Matcher.Matcher_2, Bug_Class_1_ICommandRuntimeFactoryMatchers.Matcher). fix: report analyzer diagnostics per type at in-source locations #4 documents this as a known limitation.

Change

The matcher role is now explicit and local to the type:

[OverloadMatcher]
internal interface UserMatchers
{
    [GenerateOverloads(nameof(paramB))]
    void UpdateUser(int paramA, bool paramB);
}

Situation	Behavior
Type marked with [OverloadMatcher]	Matcher, never a target, whether or not anything references it
Unmarked type in Matchers	Not used as a matcher, keeps its own role. MOG020 (Error) at every typeof reference
[GenerateMethodOverloads] on a matcher type, or Matchers on one of its methods	Ignored. MOG021 (Error) at that attribute. Other [GenerateOverloads] of the matcher method still apply
Methods of a matcher type without [GenerateOverloads]	Neither matcher methods nor targets (unchanged)

New [OverloadMatcher] attribute: Class | Struct | Interface, no AllowMultiple, embedded like the other attributes.

Implementation

• TypeModel.IsMatcher comes from the marker (Parser.IsMatcherType). OverloadPlanBuilder skips methods of matcher types via this flag instead of the global set of referenced matcher types. Parser.ExtractMatcherTypes ignores unmarked types. TargetFactory ignores Matchers on matcher types.
• Formal checks of matcher attributes run in one place: the new ValidateMatcherMethods step reports MOG001, MOG007–MOG011, MOG013–MOG016, MOG018 and MOG019 once, in the matcher type's own analysis, independent of any target. The matcher path of a target now skips invalid matcher attributes silently; before, it reported diagnostics at matcher locations that the analyzer discarded. Generation diagnostics (MOG003–MOG006) are reported only at targets.
• MOG020 and MOG021 are declaration checks done directly in the analyzer. The analyzer reads them from symbols and syntax, so the locations are exact, and generator inputs carry no new diagnostics or source locations (see the planned "models without locations" PR).

Breaking change

Types listed in Matchers must be marked with [OverloadMatcher]. Unmarked types produce MOG020 and are ignored. Documented in the README.

Minor: a matcher method whose [GenerateOverloads] combines Matchers with window anchors or ExcludeAny was skipped entirely before (MOG012/MOG017, never visible at the matcher). Now only that attribute is ignored (MOG021).

Diagnostics before/after (acceptance sources, in-memory analyzer dump)

All 35 matcher types are marked. The suggested grep for Matchers = [...] missed SupplyParameterType_Class_12, which spans lines; MOG020 flagged its two matchers.

	Before	After
Total	39	39
In matcher types	2 × MOG006, live, false positives	0
In targets	37	the same 37 (identical apart from line shifts by the inserted attribute)
New	–	MOG020 in Class_46, MOG021 in Class_47 (new cases, suppressed as expected)

Generated overloads of all existing acceptance cases are unchanged.

Tests

Tests follow the acceptance-criteria approach (docs/testing.md):

• Class_46: an unmarked type in Matchers is ignored and keeps its own role, so its own overload is generated. MOG020 is reported at both typeof references (type and method level).
• Class_47: [GenerateMethodOverloads] on a matcher type (MOG021).
• Class_48: one matcher per path of the matcher validation step (invalid window MOG001, redundant anchors MOG008, parameterless MOG011, invalid bucket MOG013, invalid SupplyParameterType MOG014) and Matchers on a matcher method (MOG021). The error kinds themselves are already covered at targets. A target still gets the overload from the valid attribute of the MOG021 matcher.
• Class_49: an unused matcher in the shape of Class_4_Matcher produces no overloads and no MOG006 (the original false positive).
• Matchers that expect diagnostics are abstract classes, because the acceptance infrastructure maps diagnostics only inside classes.
• UnmarkedMatcherTests checks on the acceptance output that MOG020 is reported twice in Class_46. The diagnostics comparison works on IDs per class and cannot count.
• OverloadMatcher usages on class, struct and interface for AttributeUsageTests. AttributesOnlyTests checks that the attribute is emitted. The diagnostics snapshot gains MOG020 and MOG021. DiagnosticSuppressionTests marks its in-memory matcher.
• Mutation checks:
  • disabling ValidateMatcherMethods fails the five validation cases of Class_48
  • treating matcher methods as targets fails Class_49 (among others)
  • skipping a matcher method because of its Matchers attribute fails Class_48

Verification

• dotnet test --nologo: 131 passed. The feat! commit alone: 120 passed.
• dotnet build ref/...csproj -c Release -nodeReuse:false --no-incremental with TenekonMethodOverloadsSourceGeneratorAttributesOnly=false and =true: 0 errors, 0 MOG warnings. The CS8625 warnings are unchanged (59 in the full build).
• Patch coverage measured locally: 89.0%. Uncovered are mostly the report guards for SupplyParameterType errors on matcher types. The acceptance project has no case for type-level SupplyParameterType errors at all (pre-existing). No tests were added only for coverage.

Out of scope

• Generator models without source locations (separate PR).
• Matcher types from other assemblies.
• Acceptance infrastructure gaps (interfaces not mapped, comparison per class only, regex parsing of extension blocks, return type missing from the key).

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 88.96104% with 17 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
....SourceGenerator/Generation/OverloadPlanBuilder.cs	81.15%	5 Missing and 8 partials ⚠️
...rceGenerator/MethodOverloadsDiagnosticsAnalyzer.cs	92.30%	0 Missing and 4 partials ⚠️

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