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The && operator is the logical AND operator in Rust. It evaluates two boolean expressions and returns true if and only if both operands evaluate to true.

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Syntax and Type Constraints

The operator requires exactly two operands, both of which must strictly resolve to the bool primitive type. Rust does not support implicit type coercion for booleans (i.e., there are no “truthy” or “falsy” values). 
let a: bool = true;
let b: bool = false;
let result: bool = a && b; // Evaluates to false
Attempting to use non-boolean types will result in a compile-time E0308 (mismatched types) error: 
// Compilation error: expected `bool`, found integer
let invalid = 1 && true;

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Short-Circuit Evaluation

The && operator employs strict left-to-right short-circuit (lazy) evaluation.
  1. The left-hand operand is evaluated first.
  2. If the left-hand operand evaluates to false, the overall expression immediately yields false.
  3. The right-hand operand is never evaluated if the left-hand operand is false.
This behavior guarantees safe execution when the right-hand expression contains operations that could panic, cause side effects, or perform expensive computations. 
fn expensive_computation() -> bool {
    // This function is never called in the expression below
    true
}

let is_valid = false;
// The right side is ignored; no panic occurs and the function is not invoked.
let result = is_valid && expensive_computation();

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Operator Precedence

In Rust’s expression parsing, && has a specific precedence level:
  • Lower than comparison operators (==, !=, <, >, <=, >=) and bitwise operators (&, |, ^).
  • Higher than the logical OR operator (||) and assignment operators (=, +=, etc.).
Because it binds less tightly than comparison operators, parentheses are not required when combining relational expressions: 
let x = 5;
let y = 10;

// Parsed as: (x > 0) && (y < 20)
let in_range = x > 0 && y < 20;
However, because && binds more tightly than ||, expressions mixing the two will evaluate the && segments first: 
let a = true;
let b = false;
let c = true;

// Parsed as: a || (b && c)
let mixed = a || b && c;

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Trait Implementation Restrictions

Unlike the bitwise AND operator (&), which can be overloaded for custom types via the std::ops::BitAnd trait, the logical && operator cannot be overloaded. Rust enforces this restriction at the language level to preserve the guarantee of short-circuit evaluation. If && were backed by a trait method (e.g., fn logical_and(self, rhs: Self)), both operands would have to be fully evaluated before being passed as arguments to the function, which would fundamentally break short-circuiting semantics.
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