test: clean up run.go

• Inline check function because it's more readable.
• Delete toolPath because it was unused.
• Use strings.TrimPrefix because it's simpler.
• Remove out variable because its value was unused.
• Rename serr to err because it's more consistent.

Change-Id: I084fb4f8b399578834d5eea29a673c386cf3a357
Reviewed-on: https://go-review.googlesource.com/c/go/+/218701
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Hajime Hoshi <hajimehoshi@gmail.com>

test/run.go

@@ -166,14 +166,6 @@ func main() {
 	}
 }
 
-func toolPath(name string) string {
-	p := filepath.Join(os.Getenv("GOROOT"), "bin", "tool", name)
-	if _, err := os.Stat(p); err != nil {
-		log.Fatalf("didn't find binary at %s", p)
-	}
-	return p
-}
-
 // goTool reports the path of the go tool to use to run the tests.
 // If possible, use the same Go used to run run.go, otherwise
 // fallback to the go version found in the PATH.
@@ -201,10 +193,14 @@ func shardMatch(name string) bool {
 
 func goFiles(dir string) []string {
 	f, err := os.Open(dir)
-	check(err)
+	if err != nil {
+		log.Fatal(err)
+	}
 	dirnames, err := f.Readdirnames(-1)
 	f.Close()
-	check(err)
+	if err != nil {
+		log.Fatal(err)
+	}
 	names := []string{}
 	for _, name := range dirnames {
 		if !strings.HasPrefix(name, ".") && strings.HasSuffix(name, ".go") && shardMatch(name) {
@@ -262,12 +258,6 @@ type skipError string
 
 func (s skipError) Error() string { return string(s) }
 
-func check(err error) {
-	if err != nil {
-		log.Fatal(err)
-	}
-}
-
 // test holds the state of a test.
 type test struct {
 	dir, gofile string
@@ -361,7 +351,9 @@ func goDirPackages(longdir string, singlefilepkgs bool) ([][]string, error) {
 	for _, file := range files {
 		name := file.Name()
 		pkgname, err := getPackageNameFromSource(filepath.Join(longdir, name))
-		check(err)
+		if err != nil {
+			log.Fatal(err)
+		}
 		i, ok := m[pkgname]
 		if singlefilepkgs || !ok {
 			i = len(pkgs)
@@ -500,9 +492,7 @@ func (t *test) run() {
 		// skip first line
 		action = action[nl+1:]
 	}
-	if strings.HasPrefix(action, "//") {
-		action = action[2:]
-	}
+	action = strings.TrimPrefix(action, "//")
 
 	// Check for build constraints only up to the actual code.
 	pkgPos := strings.Index(t.src, "\npackage")
@@ -601,7 +591,9 @@ func (t *test) run() {
 	}
 
 	err = ioutil.WriteFile(filepath.Join(t.tempDir, t.gofile), srcBytes, 0644)
-	check(err)
+	if err != nil {
+		log.Fatal(err)
+	}
 
 	// A few tests (of things like the environment) require these to be set.
 	if os.Getenv("GOOS") == "" {
@@ -814,8 +806,10 @@ func (t *test) run() {
 			pflags = append(pflags, flags...)
 			if setpkgpaths {
 				fp := filepath.Join(longdir, gofiles[0])
-				pkgname, serr := getPackageNameFromSource(fp)
-				check(serr)
+				pkgname, err := getPackageNameFromSource(fp)
+				if err != nil {
+					log.Fatal(err)
+				}
 				pflags = append(pflags, "-p", pkgname)
 			}
 			_, err := compileInDir(runcmd, longdir, pflags, localImports, gofiles...)
@@ -967,13 +961,13 @@ func (t *test) run() {
 		longdirgofile := filepath.Join(filepath.Join(cwd, t.dir), t.gofile)
 		cmd = append(cmd, flags...)
 		cmd = append(cmd, longdirgofile)
-		out, err := runcmd(cmd...)
+		_, err := runcmd(cmd...)
 		if err != nil {
 			t.err = err
 			return
 		}
 		cmd = []string{"./a.exe"}
-		out, err = runcmd(append(cmd, args...)...)
+		out, err := runcmd(append(cmd, args...)...)
 		if err != nil {
 			t.err = err
 			return
@@ -1129,7 +1123,9 @@ func (t *test) String() string {
 func (t *test) makeTempDir() {
 	var err error
 	t.tempDir, err = ioutil.TempDir("", "")
-	check(err)
+	if err != nil {
+		log.Fatal(err)
+	}
 	if *keep {
 		log.Printf("Temporary directory is %s", t.tempDir)
 	}