Avoid memory allocation for interface enforcer

Summary:
Old:
```
// Compile time interface enforcer
var _ thrift.Struct = &Foo{}
```
New:
```
// Compile time interface enforcer
var _ thrift.Struct = (*Foo)(nil)
```

Why?
* Unnecessary memory allocation is avoided. Profit.

Reviewed By: podtserkovskiy

Differential Revision: D57456069

fbshipit-source-id: 89c05b773e9117a5b5ab20dc528ca0b432282f72

third-party/thrift/src/thrift/compiler/generate/templates/go/svc/client.mustache

@@ -29,7 +29,7 @@ type {{service:go_name}}ChannelClient struct {
     ch thrift.RequestChannel
 }
 // Compile time interface enforcer
-var _ {{service:go_name}}ChannelClientInterface = &{{service:go_name}}ChannelClient{}
+var _ {{service:go_name}}ChannelClientInterface = (*{{service:go_name}}ChannelClient)(nil)
 
 func New{{service:go_name}}ChannelClient(channel thrift.RequestChannel) *{{service:go_name}}ChannelClient {
     return &{{service:go_name}}ChannelClient{
@@ -57,8 +57,8 @@ type {{service:go_name}}Client struct {
     Mu       sync.Mutex
 }
 // Compile time interface enforcer
-var _ {{service:go_name}}ClientInterface = &{{service:go_name}}Client{}
-var _ {{service:go_name}}ContextClientInterface = &{{service:go_name}}Client{}
+var _ {{service:go_name}}ClientInterface = (*{{service:go_name}}Client)(nil)
+var _ {{service:go_name}}ContextClientInterface = (*{{service:go_name}}Client)(nil)
 
 func New{{service:go_name}}Client(prot thrift.Protocol) *{{service:go_name}}Client {
     return &{{service:go_name}}Client{

third-party/thrift/src/thrift/compiler/generate/templates/go/svc/processor.mustache

@@ -34,7 +34,7 @@ type {{service:go_name}}Processor struct {
     {{/service:extends?}}
 }
 // Compile time interface enforcer
-var _ thrift.ProcessorContext = &{{service:go_name}}Processor{}
+var _ thrift.ProcessorContext = (*{{service:go_name}}Processor)(nil)
 
 func New{{service:go_name}}Processor(handler {{service:go_name}}) *{{service:go_name}}Processor {
     p := &{{service:go_name}}Processor{
@@ -102,7 +102,7 @@ type {{> svc/proc_func_name}} struct {
     handler {{service:go_name}}
 }
 // Compile time interface enforcer
-var _ thrift.ProcessorFunctionContext = &{{> svc/proc_func_name}}{}
+var _ thrift.ProcessorFunctionContext = (*{{> svc/proc_func_name}})(nil)
 
 func (p *{{> svc/proc_func_name}}) Read(iprot thrift.Format) (thrift.Struct, thrift.Exception) {
     args := newReq{{service:go_name}}{{function:go_name}}()

third-party/thrift/src/thrift/compiler/generate/templates/go/types/struct_definition.mustache

@@ -26,9 +26,9 @@ type {{struct:go_name}} struct {
 {{/struct:fields_sorted}}
 }
 // Compile time interface enforcer
-var _ thrift.Struct = &{{struct:go_name}}{}
+var _ thrift.Struct = (*{{struct:go_name}})(nil)
 {{#struct:resp?}}
-var _ thrift.WritableResult = &{{struct:go_name}}{}
+var _ thrift.WritableResult = (*{{struct:go_name}})(nil)
 
 {{! TODO: resp struct is an internal implementation detail. Can we unexport it? }}
 // Deprecated: {{struct:go_public_resp_name}} is deprecated, since it is supposed to be internal.

third-party/thrift/src/thrift/compiler/test/fixtures/adapter/out/go/gen-go/module/svcs.go

@@ -47,7 +47,7 @@ type ServiceChannelClient struct {
     ch thrift.RequestChannel
 }
 // Compile time interface enforcer
-var _ ServiceChannelClientInterface = &ServiceChannelClient{}
+var _ ServiceChannelClientInterface = (*ServiceChannelClient)(nil)
 
 func NewServiceChannelClient(channel thrift.RequestChannel) *ServiceChannelClient {
     return &ServiceChannelClient{
@@ -64,8 +64,8 @@ type ServiceClient struct {
     Mu       sync.Mutex
 }
 // Compile time interface enforcer
-var _ ServiceClientInterface = &ServiceClient{}
-var _ ServiceContextClientInterface = &ServiceClient{}
+var _ ServiceClientInterface = (*ServiceClient)(nil)
+var _ ServiceContextClientInterface = (*ServiceClient)(nil)
 
 func NewServiceClient(prot thrift.Protocol) *ServiceClient {
     return &ServiceClient{
@@ -107,7 +107,7 @@ type reqServiceFunc struct {
     Arg3 *Foo `thrift:"arg3,3" json:"arg3" db:"arg3"`
 }
 // Compile time interface enforcer
-var _ thrift.Struct = &reqServiceFunc{}
+var _ thrift.Struct = (*reqServiceFunc)(nil)
 
 // Deprecated: ServiceFuncArgsDeprecated is deprecated, since it is supposed to be internal.
 type ServiceFuncArgsDeprecated = reqServiceFunc
@@ -379,8 +379,8 @@ type respServiceFunc struct {
     Success *MyI32_4873 `thrift:"success,0,optional" json:"success,omitempty" db:"success"`
 }
 // Compile time interface enforcer
-var _ thrift.Struct = &respServiceFunc{}
-var _ thrift.WritableResult = &respServiceFunc{}
+var _ thrift.Struct = (*respServiceFunc)(nil)
+var _ thrift.WritableResult = (*respServiceFunc)(nil)
 
 // Deprecated: ServiceFuncResultDeprecated is deprecated, since it is supposed to be internal.
 type ServiceFuncResultDeprecated = respServiceFunc
@@ -538,7 +538,7 @@ type ServiceProcessor struct {
     handler            Service
 }
 // Compile time interface enforcer
-var _ thrift.ProcessorContext = &ServiceProcessor{}
+var _ thrift.ProcessorContext = (*ServiceProcessor)(nil)
 
 func NewServiceProcessor(handler Service) *ServiceProcessor {
     p := &ServiceProcessor{
@@ -584,7 +584,7 @@ type procFuncServiceFunc struct {
     handler Service
 }
 // Compile time interface enforcer
-var _ thrift.ProcessorFunctionContext = &procFuncServiceFunc{}
+var _ thrift.ProcessorFunctionContext = (*procFuncServiceFunc)(nil)
 
 func (p *procFuncServiceFunc) Read(iprot thrift.Format) (thrift.Struct, thrift.Exception) {
     args := newReqServiceFunc()
@@ -660,7 +660,7 @@ type AdapterServiceChannelClient struct {
     ch thrift.RequestChannel
 }
 // Compile time interface enforcer
-var _ AdapterServiceChannelClientInterface = &AdapterServiceChannelClient{}
+var _ AdapterServiceChannelClientInterface = (*AdapterServiceChannelClient)(nil)
 
 func NewAdapterServiceChannelClient(channel thrift.RequestChannel) *AdapterServiceChannelClient {
     return &AdapterServiceChannelClient{
@@ -677,8 +677,8 @@ type AdapterServiceClient struct {
     Mu       sync.Mutex
 }
 // Compile time interface enforcer
-var _ AdapterServiceClientInterface = &AdapterServiceClient{}
-var _ AdapterServiceContextClientInterface = &AdapterServiceClient{}
+var _ AdapterServiceClientInterface = (*AdapterServiceClient)(nil)
+var _ AdapterServiceContextClientInterface = (*AdapterServiceClient)(nil)
 
 func NewAdapterServiceClient(prot thrift.Protocol) *AdapterServiceClient {
     return &AdapterServiceClient{
@@ -734,7 +734,7 @@ func (c *AdapterServiceClient) AdaptedTypesContext(ctx context.Context, arg *Hea
 type reqAdapterServiceCount struct {
 }
 // Compile time interface enforcer
-var _ thrift.Struct = &reqAdapterServiceCount{}
+var _ thrift.Struct = (*reqAdapterServiceCount)(nil)
 
 // Deprecated: AdapterServiceCountArgsDeprecated is deprecated, since it is supposed to be internal.
 type AdapterServiceCountArgsDeprecated = reqAdapterServiceCount
@@ -810,8 +810,8 @@ type respAdapterServiceCount struct {
     Success *CountingStruct `thrift:"success,0,optional" json:"success,omitempty" db:"success"`
 }
 // Compile time interface enforcer
-var _ thrift.Struct = &respAdapterServiceCount{}
-var _ thrift.WritableResult = &respAdapterServiceCount{}
+var _ thrift.Struct = (*respAdapterServiceCount)(nil)
+var _ thrift.WritableResult = (*respAdapterServiceCount)(nil)
 
 // Deprecated: AdapterServiceCountResultDeprecated is deprecated, since it is supposed to be internal.
 type AdapterServiceCountResultDeprecated = respAdapterServiceCount
@@ -969,7 +969,7 @@ type reqAdapterServiceAdaptedTypes struct {
     Arg *HeapAllocated `thrift:"arg,1" json:"arg" db:"arg"`
 }
 // Compile time interface enforcer
-var _ thrift.Struct = &reqAdapterServiceAdaptedTypes{}
+var _ thrift.Struct = (*reqAdapterServiceAdaptedTypes)(nil)
 
 // Deprecated: AdapterServiceAdaptedTypesArgsDeprecated is deprecated, since it is supposed to be internal.
 type AdapterServiceAdaptedTypesArgsDeprecated = reqAdapterServiceAdaptedTypes
@@ -1124,8 +1124,8 @@ type respAdapterServiceAdaptedTypes struct {
     Success *HeapAllocated `thrift:"success,0,optional" json:"success,omitempty" db:"success"`
 }
 // Compile time interface enforcer
-var _ thrift.Struct = &respAdapterServiceAdaptedTypes{}
-var _ thrift.WritableResult = &respAdapterServiceAdaptedTypes{}
+var _ thrift.Struct = (*respAdapterServiceAdaptedTypes)(nil)
+var _ thrift.WritableResult = (*respAdapterServiceAdaptedTypes)(nil)
 
 // Deprecated: AdapterServiceAdaptedTypesResultDeprecated is deprecated, since it is supposed to be internal.
 type AdapterServiceAdaptedTypesResultDeprecated = respAdapterServiceAdaptedTypes
@@ -1287,7 +1287,7 @@ type AdapterServiceProcessor struct {
     handler            AdapterService
 }
 // Compile time interface enforcer
-var _ thrift.ProcessorContext = &AdapterServiceProcessor{}
+var _ thrift.ProcessorContext = (*AdapterServiceProcessor)(nil)
 
 func NewAdapterServiceProcessor(handler AdapterService) *AdapterServiceProcessor {
     p := &AdapterServiceProcessor{
@@ -1335,7 +1335,7 @@ type procFuncAdapterServiceCount struct {
     handler AdapterService
 }
 // Compile time interface enforcer
-var _ thrift.ProcessorFunctionContext = &procFuncAdapterServiceCount{}
+var _ thrift.ProcessorFunctionContext = (*procFuncAdapterServiceCount)(nil)
 
 func (p *procFuncAdapterServiceCount) Read(iprot thrift.Format) (thrift.Struct, thrift.Exception) {
     args := newReqAdapterServiceCount()
@@ -1386,7 +1386,7 @@ type procFuncAdapterServiceAdaptedTypes struct {
     handler AdapterService
 }
 // Compile time interface enforcer
-var _ thrift.ProcessorFunctionContext = &procFuncAdapterServiceAdaptedTypes{}
+var _ thrift.ProcessorFunctionContext = (*procFuncAdapterServiceAdaptedTypes)(nil)
 
 func (p *procFuncAdapterServiceAdaptedTypes) Read(iprot thrift.Format) (thrift.Struct, thrift.Exception) {
     args := newReqAdapterServiceAdaptedTypes()