refactor: add nil assignments to verify interface implementations

cmd/gazelle/fix-update.go

@@ -71,6 +71,8 @@ func getUpdateConfig(c *config.Config) *updateConfig {
 	return c.Exts[updateName].(*updateConfig)
 }
 
+var _ config.Configurer = (*updateConfigurer)(nil)
+
 type updateConfigurer struct {
 	mode           string
 	recursive      bool

cmd/gazelle/metaresolver.go

@@ -77,7 +77,7 @@ type inverseMapKindResolver struct {
 	delegate resolve.Resolver
 }
 
-var _ resolve.Resolver = inverseMapKindResolver{}
+var _ resolve.Resolver = (*inverseMapKindResolver)(nil)
 
 func (imkr inverseMapKindResolver) Name() string {
 	return imkr.delegate.Name()

cmd/gazelle/update-repos.go

@@ -50,6 +50,8 @@ func getUpdateReposConfig(c *config.Config) *updateReposConfig {
 	return c.Exts[updateReposName].(*updateReposConfig)
 }
 
+var _ config.Configurer = (*updateReposConfigurer)(nil)
+
 type updateReposConfigurer struct{}
 
 type macroFlag struct {

config/config.go

@@ -195,6 +195,8 @@ type Configurer interface {
 	Configure(c *Config, rel string, f *rule.File)
 }
 
+var _ Configurer = (*CommonConfigurer)(nil)
+
 // CommonConfigurer handles language-agnostic command-line flags and directives,
 // i.e., those that apply to Config itself and not to Config.Exts.
 type CommonConfigurer struct {

internal/gazellebinarytest/xlang.go

@@ -29,6 +29,8 @@ import (
 	"github.com/bazelbuild/bazel-gazelle/rule"
 )
 
+var _ config.Configurer = (*xlang)(nil)
+
 type xlang struct{}
 
 func NewLanguage() language.Language {

resolve/config.go

@@ -114,6 +114,8 @@ func getResolveConfig(c *config.Config) *resolveConfig {
 	return c.Exts[resolveName].(*resolveConfig)
 }
 
+var _ config.Configurer = (*Configurer)(nil)
+
 type Configurer struct{}
 
 func (*Configurer) RegisterFlags(fs *flag.FlagSet, cmd string, c *config.Config) {

rule/rule.go

@@ -514,7 +514,7 @@ type rulesByKindAndName struct {
 }
 
 // type checking
-var _ sort.Interface = rulesByKindAndName{}
+var _ sort.Interface = (*rulesByKindAndName)(nil)
 
 func (s rulesByKindAndName) Len() int {
 	return len(s.rules)
@@ -539,7 +539,7 @@ type loadsByName struct {
 }
 
 // type checking
-var _ sort.Interface = loadsByName{}
+var _ sort.Interface = (*loadsByName)(nil)
 
 func (s loadsByName) Len() int {
 	return len(s.loads)
@@ -1144,7 +1144,7 @@ func CheckInternalVisibility(rel, visibility string) string {
 
 type byAttrName []KeyValue
 
-var _ sort.Interface = byAttrName{}
+var _ sort.Interface = (*byAttrName)(nil)
 
 func (s byAttrName) Len() int {
 	return len(s)

rule/value.go

@@ -141,13 +141,13 @@ func (s SelectStringListValue) BzlExpr() bzl.Expr {
 // ExprFromValue converts a value into an expression that can be written into
 // a Bazel build file. The following types of values can be converted:
 //
-//   * bools, integers, floats, strings.
-//   * labels (converted to strings).
-//   * slices, arrays (converted to lists).
-//   * maps (converted to select expressions; keys must be rules in
+//   - bools, integers, floats, strings.
+//   - labels (converted to strings).
+//   - slices, arrays (converted to lists).
+//   - maps (converted to select expressions; keys must be rules in
 //     @io_bazel_rules_go//go/platform).
-//   * GlobValue (converted to glob expressions).
-//   * PlatformStrings (converted to a concatenation of a list and selects).
+//   - GlobValue (converted to glob expressions).
+//   - PlatformStrings (converted to a concatenation of a list and selects).
 //
 // Converting unsupported types will cause a panic.
 func ExprFromValue(val interface{}) bzl.Expr {
@@ -216,7 +216,7 @@ func mapKeyString(k reflect.Value) string {
 
 type byString []reflect.Value
 
-var _ sort.Interface = byString{}
+var _ sort.Interface = (*byString)(nil)
 
 func (s byString) Len() int {
 	return len(s)

walk/config.go

@@ -62,6 +62,8 @@ func (wc *walkConfig) shouldFollow(rel, base string) bool {
 	return matchAnyGlob(wc.follow, path.Join(rel, base))
 }
 
+var _ config.Configurer = (*Configurer)(nil)
+
 type Configurer struct{}
 
 func (*Configurer) RegisterFlags(fs *flag.FlagSet, cmd string, c *config.Config) {

walk/walk_test.go

@@ -329,6 +329,8 @@ func testConfig(t *testing.T, dir string) (*config.Config, []config.Configurer)
 	return c, cexts
 }
 
+var _ config.Configurer = (*testConfigurer)(nil)
+
 type testConfigurer struct {
 	configure func(c *config.Config, rel string, f *rule.File)
 }