Found unnecessary multiple type assertion SCC-S1034
Anti-pattern
Major
5 months ago
—
3 years old
assigning the result of this type assertion to a variable (switch outputWriter := outputWriter.(type)) could eliminate type assertions in switch cases
171 return false, "", err
172 }
173
174 switch outputWriter.(type) {175 case io.WriteCloser:
176 outputWriter.(io.WriteCloser).Close()
177 }assigning the result of this type assertion to a variable (switch obj := obj.(type)) could eliminate type assertions in switch cases
234// not support int64 on 32-bit platform
235func (m Max) IsSatisfied(obj interface{}) bool {
236 var v int
237 switch obj.(type) {238 case int64:
239 if wordsize == 32 {
240 return falseassigning the result of this type assertion to a variable (switch obj := obj.(type)) could eliminate type assertions in switch cases
188// not support int64 on 32-bit platform
189func (m Min) IsSatisfied(obj interface{}) bool {
190 var v int
191 switch obj.(type) {192 case int64:
193 if wordsize == 32 {
194 return falseassigning the result of this type assertion to a variable (switch f := f.(type)) could eliminate type assertions in switch cases
789
790func formatPattern(f interface{}, v ...interface{}) string {
791 var msg string
792 switch f.(type) {793 case string:
794 msg = f.(string)
795 if len(v) == 0 {
Description
Instead of asserting the type every time in a switch statement, assign the
result of type assertion to a variable and use it.
A type assertion provides access to an interface's underlying concrete value.
The following statement asserts that the interface value i holds the concrete type
T assigns the underlying T value to the variable t. The statement will trigger
panic if i does not hold a T.
t := i.(T)
Hence, the recommendation of using the result of type assertion is idiomatic and straightforward. Also, it saves from the following bad practice:
switch x.(type) {
case int:
// Triggers a panic as "x" doesn't hold
// concrete type "string" but "int"
fmt.Println(x.(string))
}
Bad practice
switch x.(type) {
case int:
fmt.Println(x.(int))
}
Recommended
switch x := x.(type) {
case int:
fmt.Println(x)
}