internal: fix unused errors reported by ineffassign

Updates #76704

Author: linsite

internal/goroot/importcfg.go

@@ -16,37 +16,29 @@ import (
 	"sync"
 )
 
-var (
-	stdlibPkgfileMap map[string]string
-	stdlibPkgfileErr error
-	once             sync.Once
-)
-
 // PkgfileMap returns a map of package paths to the location on disk
 // of the .a file for the package.
 // The caller must not modify the map.
 func PkgfileMap() (map[string]string, error) {
-	once.Do(func() {
+	return sync.OnceValues(func() (map[string]string, error) {
 		m := make(map[string]string)
 		output, err := exec.Command("go", "list", "-export", "-e", "-f", "{{.ImportPath}} {{.Export}}", "std", "cmd").Output()
 		if err != nil {
-			stdlibPkgfileErr = err
+			return m, err
 		}
 		for line := range strings.SplitSeq(string(output), "\n") {
 			if line == "" {
 				continue
 			}
 			sp := strings.SplitN(line, " ", 2)
 			if len(sp) != 2 {
-				err = fmt.Errorf("determining pkgfile map: invalid line in go list output: %q", line)
-				return
+				return m, fmt.Errorf("determining pkgfile map: invalid line in go list output: %q", line)
 			}
 			importPath, export := sp[0], sp[1]
 			if export != "" {
 				m[importPath] = export
 			}
 		}
-		stdlibPkgfileMap = m
-	})
-	return stdlibPkgfileMap, stdlibPkgfileErr
+		return m, nil
+	})()
 }

internal/imports/sourcex_test.go

@@ -78,6 +78,9 @@ func TestSource(t *testing.T) {
 	opts := imports.Options{}
 	// ApplyFixes needs a non-nil opts
 	got, err := imports.ApplyFixes(fixes, "tfile.go", []byte(fx), &opts, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	fxwant := "package main\n\nimport \"bar.com/foo\"\n\nvar _ = foo.Foo\nvar _ = foo.Bar\n"
 	if diff := cmp.Diff(string(got), fxwant); diff != "" {