fix: extend support of parenthesized expression as receiver

check/check.go

@@ -908,15 +908,20 @@ func recvPrefix(recv *ast.FieldList) string {
 		}
 		expr = star.X
 	}
+
+	return identName(expr)
+}
+
+func identName(expr ast.Expr) string {
 	switch expr := expr.(type) {
 	case *ast.Ident:
 		return expr.Name + "."
 	case *ast.IndexExpr:
-		return expr.X.(*ast.Ident).Name + "."
+		return identName(expr.X)
 	case *ast.ParenExpr:
-		return expr.X.(*ast.Ident).Name + "."
+		return identName(expr.X)
 	case *ast.IndexListExpr:
-		return expr.X.(*ast.Ident).Name + "."
+		return identName(expr.X)
 	default:
 		panic(fmt.Sprintf("unexpected receiver AST node: %T", expr))
 	}

testdata/script/parenthesized_expression.txtar

@@ -7,6 +7,7 @@ module testdata.tld/foo
 go 1.18
 -- stdout.golden --
 foo.go:7:37: (*FooType).multImplsMethod - a is unused
+foo.go:12:44: (*FooType).multImplsMethod2 - a is unused
 -- foo.go --
 package foo
 
@@ -18,3 +19,8 @@ func (f *(FooType)) multImplsMethod(a int) int64 {
 	DoWork()
 	return 3
 }
+
+func (f *((((FooType))))) multImplsMethod2(a int) int64 {
+	DoWork()
+	return 3
+}