bug: fix check of subtest builder from another file

pkg/analyzer/analyzer.go

@@ -412,8 +412,8 @@ func unwrapTestingFunctionBuilding(pass *analysis.Pass, expr ast.Expr, testFuncT
 		funcDecl.Body = f.Body
 		funcDecl.Type = f.Type
 	case *ast.Ident:
-		funObjDecl, ok := f.Obj.Decl.(*ast.FuncDecl)
-		if !ok {
+		funObjDecl := findFunctionDeclaration(pass, f)
+		if funObjDecl == nil {
 			return nil
 		}
 
@@ -533,3 +533,32 @@ func findSelectroDeclaration(pass *analysis.Pass, expr *ast.SelectorExpr) *ast.F
 
 	return nil
 }
+
+// findFunctionDeclaration returns function declaration called by identity.
+func findFunctionDeclaration(pass *analysis.Pass, ident *ast.Ident) *ast.FuncDecl {
+	if ident.Obj != nil {
+		if funObjDecl, ok := ident.Obj.Decl.(*ast.FuncDecl); ok {
+			return funObjDecl
+		}
+	}
+
+	obj := pass.TypesInfo.ObjectOf(ident)
+	if obj == nil {
+		return nil
+	}
+
+	for _, file := range pass.Files {
+		for _, decl := range file.Decls {
+			funcDecl, ok := decl.(*ast.FuncDecl)
+			if !ok {
+				continue
+			}
+
+			if funcDecl.Name.Pos() == obj.Pos() {
+				return funcDecl
+			}
+		}
+	}
+
+	return nil
+}

pkg/analyzer/testdata/src/t/s.go

@@ -36,6 +36,7 @@ func (sh subhelper) anotherCheck(t *testing.T) {} // want "test helper function
 func TestSubtestWithBuilder(t *testing.T) {
 	t.Run("sub1", subtestBuilder("first"))
 	t.Run("sub2", subtestBuilder("second"))
+	t.Run("sub_from_other_file", subtestBuilderAnotherFile())
 	t.Run("anon", func() func(t *testing.T) { return func(t *testing.T) {} }())
 
 	fixture := subtestFixture{}

pkg/analyzer/testdata/src/t/ss.go

@@ -0,0 +1,7 @@
+package t
+
+import "testing"
+
+func subtestBuilderAnotherFile() func(*testing.T) {
+	return func(t *testing.T) {}
+}