Limitations and constraints of return value type inference in Go language

The Go language return value type inference function is only applicable to single return statements, and cannot be inferred for interface{} return values ​​and built-in functions. Specific limitations include: only applicable to single return statements. Cannot infer the interface{} return value. Unable to infer built-in function type.

Limitations and constraints of Go language return value type inference

In Go language, return value type inference is usually very convenient , which can save a lot of typing when writing code. However, it also has some limitations and constraints that may cause unexpected results or compilation errors.

1. Only applicable to single return statements

The function of return value type inference is only applicable to single return statements. If a function has multiple return statements, the type must be explicitly specified for each return statement. For example:

func sum(a, b int) (int, error) {
  if a < 0 || b < 0 {
    return 0, errors.New("invalid input")
  }
  return a + b, nil
}

2. Unable to infer the return value of interface{}

Go language does not support interface{} type of value for return value type inference. If a function returns a value of type interface{}, its type must be specified explicitly. For example:

type Animal interface {
  Speak()
}

func getAnimal() interface{} {
  return new(Cat) // returns a pointer to a Cat implementation
}

3. Unable to infer the built-in function type

Built-in functions in Go language, such as fmt.Println() and math.Pow(), the return value type cannot be inferred. That is, the return value type must be explicitly specified for it. For example:

package main

import "fmt"

func main() {
  v := fmt.Println("Hello, world!") // error: cannot infer type from
}

Practical case

The following is an example of a function with return value type inference:

func getLength(s string) int {
  return len(s)
}

In this function, the return value The type Int is inferred through the len() function.

Note:

If you are unsure of the return type, it is recommended to always use an explicit type. This makes the code more readable and avoids potential compilation errors.

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