Go Labeled Statement

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Syntax

LabelName: Statement

LabelName:
    for {
        // ...
    }

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Scope and Namespace

• Function Scope: Labels are scoped to the function in which they are declared. They are not block-scoped. A label declared anywhere in a function is visible throughout the entire function, but cannot be referenced from nested functions, closures, or outside the function.
• Independent Namespace: Labels exist in a separate namespace from variables, types, and functions. A label can share an identifier with a variable without causing a shadowing conflict or compilation error.
• Strict Utilization: Go enforces strict label utilization. Declaring a label without subsequently referencing it with a goto, break, or continue statement results in a compile-time error (label X defined and not used).

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Control Flow Mechanics

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1. break

Outer:
    for i := 0; i < 10; i++ {
        switch i {
        case 5:
            break Outer // Terminates the 'for' loop, not just the 'switch'
        }
    }

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2. continue

LoopTarget:
    for i := 0; i < 3; i++ {
        for j := 0; j < 3; j++ {
            if j == 1 {
                continue LoopTarget // Advances 'i', skipping the rest of the inner loop
            }
        }
    }

​

3. goto

• A goto statement must not cause any variables to come into scope that were not already in scope at the point of the goto.
• A goto cannot jump into a nested block from outside that block.

func gotoMechanics() {
    goto ValidTarget // Allowed: no new variables come into scope between here and the target

ValidTarget:
    // Execution resumes here
    
    // goto InvalidTarget // Compile error: causes 'x' to come into scope

    x := 10
    _ = x

// InvalidTarget:
    
    // goto NestedTarget // Compile error: cannot jump into a nested block
    
    {
// NestedTarget:
    }
}