[alokkumary2j]

Problem. loader.addImportsToPkgs keys packages by PkgPath and keeps the variant with MORE files, i.e. the white-box test
variant p [p.test] whenever p has an in-package _test.go. Implementation extraction therefore sees only the test variant's
*types.Named for types of p. An implementer in another package q was type-checked against the PLAIN p, so
types.Implements(Impl, p.Iface) fails for any interface method whose signature names a type declared in p (two distinct
*types.Named for the same p.Opts). Result: is_implementation edges silently missing for every cross-package implementer
of such an interface in any package that has an in-package test file.

Measured (prometheus @ 21fd457, GOWORK=off, scip-go v0.2.7):

run	discovery.Config implementers (cross-pkg)	whole module, type->interface edges (non-test files)
v0.2.7	4 (0)	1,624
NeedDeps added to the loader mode	4 (0) — not the cause	n/a
--skip-tests	37 (36) — but every test-file symbol is lost	1,905
this patch	40 (36)	1,944 (superset of both baselines: +320 / +39)
44 interfaces lose implementers on prometheus alone (Config 36, Iterator 19, AppenderV2 14, ...). Debug trace:
missing=NewDiscoverer ... wrongType=true while the method-name mask passes.

Fix (~40 lines). When types.Implements fails, compare gopls-methodsets identity: every interface method's
Id + signature fingerprint must be present in the candidate type's method set. Types with type parameters (tricky fingerprints)
stay on types.Implements only, so the fallback can only ADD edges where the type checker was fooled by the universe split.

Minimal repro.

go.mod        module example.com/impl
p/p.go        package p; type Opts struct{}; type Svc interface{ Run(o *Opts) error }
p/p_test.go   package p; import "testing"; func TestOpts(t *testing.T) { _ = Opts{} }
q/q.go        package q; import "example.com/impl/p"; type Impl struct{}; func (Impl) Run(o *p.Opts) error { return nil }

scip-go -> no is_implementation relationship from q.Impl to p.Svc (delete p/p_test.go and it appears).
With the patch the edge is emitted.

Patch: scip-go-v0.2.7-fingerprint-fallback.patch (touches internal/implementations/{extractor,implementations}.go).

Still present on v0.2.9 (173cadc): the minimal repro above emits no is_implementation relationship unpatched and emits
q.Impl# -> p.Svc# (and Impl#Run(). -> Svc#Run.) patched. The patch applies cleanly to main, and go test ./... passes.

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