Golang / GoLang Basics Interview Questions

What is the difference between a type definition and a type alias in Go?

Go has two ways to give a new name to a type, with importantly different semantics. Understanding this prevents subtle type-safety bugs and confusing compiler errors.

Type Definition vs Type Alias
Aspect	Type Definition: type T U	Type Alias: type T = U
Creates new type?	YES — T and U are distinct types	NO — T is just another name for U
Methods of U inherited?	No — T starts with no methods	Yes — T and U are identical
T → U assignment	Requires explicit conversion: U(t)	No conversion needed
Use for	Adding type safety, defining method sets	Code migration, readability aliases

// TYPE DEFINITION â new type with type safety
type Celsius    float64
type Fahrenheit float64

func (c Celsius) ToFahrenheit() Fahrenheit {
    return Fahrenheit(c*9/5 + 32)
}

var bodyTemp Celsius = 37.0
// var t Fahrenheit = bodyTemp  // COMPILE ERROR â different types!
var t Fahrenheit = bodyTemp.ToFahrenheit()  // OK

// Prevents bugs: you cannot accidentally mix temperatures
func setOven(temp Celsius)        { /* ... */ }
// setOven(Fahrenheit(350))       // COMPILE ERROR â type safety!
setOven(Celsius(180))             // OK

// TYPE ALIAS â same type, different name
type MyString = string

var s1 string   = "hello"
var s2 MyString = s1    // OK â same type
s1 = s2                 // OK â no conversion

// Built-in aliases you already use:
// byte = uint8
// rune = int32
// any  = interface{}

Take quiz

What is the key difference between 'type Celsius float64' and 'type Celsius = float64'?There is no functional difference

✗ Try again.

The first creates a new distinct type (requiring explicit conversion); the second is just an alias — the same type with a different name

✓ Correct! Well done.

Only the second form allows defining methods on Celsius

✗ Try again.

The first form is faster at runtime

✗ Try again.

Can you directly assign a Celsius value to a Fahrenheit variable if both are defined as 'type X float64'?Yes — they share the same underlying float64 type

✗ Try again.

No — they are distinct types; explicit conversion Fahrenheit(celsius) is required

✓ Correct! Well done.

Yes — Go automatically converts between numeric type definitions

✗ Try again.

Only inside the same package

✗ Try again.

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Golang / GoLang Basics Interview Questions

What is the difference between a type definition and a type alias in Go?

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