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Types - Scope and Validity

Difficulty: 🔴 Advanced Time: 10 minutes

Current Implementation Status

Important: As of Cm v0.11.0, lifetime parameters ('a, 'static, etc.) are NOT implemented.

Scope Rules

Current Cm applies these basic scope rules:

int main() {
    int* r;
    {
        int x = 5;
        r = &x; // x is destroyed at the end of this block
    }
    // Using *r would be undefined behavior (compiler doesn't detect this yet)
    return 0;
}

Basic Borrowing Rules

Currently implemented borrow checking:

1. Cannot move while borrowed - Variables with active pointers cannot be moved
2. Cannot modify while borrowed - Assignment to borrowed variables is prohibited

int main() {
    int x = 100;
    const int* px = &x;  // Borrow x

    // int y = move x;  // Error: Cannot move while borrowed
    // x = 200;         // Error: Cannot modify while borrowed

    return 0;
}

Future Implementation

The following features are planned but currently NOT implemented:

• Lifetime parameters ('a, 'static, etc.)
• Lifetime annotations
• Advanced borrow checker

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Last Updated: 2026-02-08