go/analysis/passes/unusedresult: add test for typeparams

This CL adds a test for unused results inside a function using generics.

Update golang/go#48704

Author: jmesyou

go/analysis/passes/unusedresult/testdata/src/typeparams/typeparams.go

@@ -0,0 +1,29 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+//
+//go:build go1.18
+
+package typeparams
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+)
+
+func _[T any]() {
+	fmt.Errorf("") // want "result of fmt.Errorf call not used"
+	_ = fmt.Errorf("")
+
+	errors.New("") // want "result of errors.New call not used"
+
+	err := errors.New("")
+	err.Error() // want `result of \(error\).Error call not used`
+
+	var buf bytes.Buffer
+	buf.String() // want `result of \(bytes.Buffer\).String call not used`
+
+	fmt.Sprint("")  // want "result of fmt.Sprint call not used"
+	fmt.Sprintf("") // want "result of fmt.Sprintf call not used"
+}

go/analysis/passes/unusedresult/unusedresult_test.go

@@ -9,9 +9,14 @@ import (
 
 	"golang.org/x/tools/go/analysis/analysistest"
 	"golang.org/x/tools/go/analysis/passes/unusedresult"
+	"golang.org/x/tools/internal/typeparams"
 )
 
 func Test(t *testing.T) {
 	testdata := analysistest.TestData()
-	analysistest.Run(t, testdata, unusedresult.Analyzer, "a")
+	tests := []string{"a"}
+	if typeparams.Enabled {
+		tests = append(tests, "typeparams")
+	}
+	analysistest.Run(t, testdata, unusedresult.Analyzer, tests...)
 }