accounts/abi: generate TryPack* methods for abigen v2 bindings

accounts/abi/abigen/source2.go.tpl

@@ -89,7 +89,7 @@ var (
 	{{ end }}
 
 	{{range .Calls}}
-		// Pack{{.Normalized.Name}} is the Go binding used to pack the parameters required for calling
+		// Pack{{.Normalized.Name}} is the Go binding used to pack the parameters required for calling, will panic for any error.
 		// the contract method with ID 0x{{printf "%x" .Original.ID}}.
 		//
 		// Solidity: {{.Original.String}}
@@ -101,6 +101,14 @@ var (
 			return enc
 		}
 
+		// Pack{{.Normalized.Name}} is the Go binding used to pack the parameters required for calling, return error if it failed to pack.
+		// the contract method with ID 0x{{printf "%x" .Original.ID}}.
+		//
+		// Solidity: {{.Original.String}}
+		func ({{ decapitalise $contract.Type}} *{{$contract.Type}}) TryPack{{.Normalized.Name}}({{range .Normalized.Inputs}} {{.Name}} {{bindtype .Type $structs}}, {{end}}) ([]byte, error) {
+			return {{ decapitalise $contract.Type}}.abi.Pack("{{.Original.Name}}" {{range .Normalized.Inputs}}, {{.Name}}{{end}})
+		}
+
 		{{/* Unpack method is needed only when there are return args */}}
 		{{if .Normalized.Outputs }}
 			{{ if .Structured }}
@@ -117,24 +125,23 @@ var (
 			//
 			// Solidity: {{.Original.String}}
 			func ({{ decapitalise $contract.Type}} *{{$contract.Type}}) Unpack{{.Normalized.Name}}(data []byte) (
-				{{- if .Structured}} {{.Normalized.Name}}Output,{{else}}
+				{{- if .Structured}} *{{.Normalized.Name}}Output,{{else}}
 				{{- range .Normalized.Outputs}} {{bindtype .Type $structs}},{{- end }}
 				{{- end }} error) {
 				out, err := {{ decapitalise $contract.Type}}.abi.Unpack("{{.Original.Name}}", data)
 				{{- if .Structured}}
-				outstruct := new({{.Normalized.Name}}Output)
 				if err != nil {
-					return *outstruct, err
+					return nil, err
 				}
+				outstruct := new({{.Normalized.Name}}Output)
 				{{- range $i, $t := .Normalized.Outputs}}
 				{{- if ispointertype .Type}}
 					outstruct.{{capitalise .Name}} = abi.ConvertType(out[{{$i}}], new({{underlyingbindtype .Type }})).({{bindtype .Type $structs}})
 				{{- else }}
 					outstruct.{{capitalise .Name}} = *abi.ConvertType(out[{{$i}}], new({{bindtype .Type $structs}})).(*{{bindtype .Type $structs}})
 				{{- end }}
 				{{- end }}
-				return *outstruct, err
-				{{else}}
+				return outstruct, nil{{else}}
 				if err != nil {
 					return {{range $i, $_ := .Normalized.Outputs}}{{if ispointertype .Type}}new({{underlyingbindtype .Type }}), {{else}}*new({{bindtype .Type $structs}}), {{end}}{{end}} err
 				}
@@ -145,8 +152,7 @@ var (
 				out{{$i}} := *abi.ConvertType(out[{{$i}}], new({{bindtype .Type $structs}})).(*{{bindtype .Type $structs}})
 				{{- end }}
 				{{- end}}
-				return {{range $i, $t := .Normalized.Outputs}}out{{$i}}, {{end}} err
-                {{- end}}
+				return {{range $i, $t := .Normalized.Outputs}}out{{$i}}, {{end}} nil{{- end}}
 			}
 		{{end}}
 	{{end}}