Módulos inline y visibilidad granular

mod arith { ... } se declara inline; use std::math::{abs as absolute, sign} renombra durante la importación; pub(mod) secret_factor es usable por triple (mismo módulo) pero no por el código externo.

// Feature: inline `mod foo { ... }`, `use ... as ...` rename, granular

// visibility (private, `pub`, `pub(crate)`, `pub(super)`, `pub(in ...)`,

// `pub(mod)`) and origin-preserving re-exports.

// See `specs/mod-namespace-innovations.html` (cherry-picks C1, C4).


use std::math::{abs as absolute, sign}

// Inline module — declared inside this file, not loaded from disk.

mod arith {
  // No modifier: private to canonical module `crate::arith`.

  fn private_bias() -> int { 1 }

  pub fn add(a: int, b: int) -> int { a + b + private_bias() - 1 }
  pub fn mul(a: int, b: int) -> int { a * b }

  // pub(mod) keeps the item visible to siblings inside `arith` but

  // hidden to the outside file.

  pub(mod) fn secret_factor() -> int { 3 }

  // pub(crate) crosses module boundaries only inside this crate. The

  // resolver, VM/AOT lowerers and editor all use the same canonical region.

  pub(crate) fn triple(x: int) -> int { x * secret_factor() }

  // The canonical identities are `crate::arith::scoped` and

  // `crate::arith::origin`; the local names below are only aliases.

  mod scoped {
    pub(super) fn parent_only() -> int { 4 }
    pub(in crate::arith) fn arith_only() -> int { 5 }
  }

  pub fn scoped_total() -> int {
    scoped.parent_only() + scoped.arith_only()
  }

  mod origin {
    pub(crate) fn crate_value() -> int { 6 }
    pub fn public_value() -> int { 7 }
  }

  // Plain `pub use` cannot widen `crate_value`: the alias remains crate-only

  // because the re-export retains and intersects the declaration's origin.

  pub use origin::{crate_value as via_facade, public_value}
}

// Bring two items in with renames; the alias becomes the local name.

fn main() {
  print("arith.add(2,3)    = {arith.add(2, 3)}")       // 5

  print("arith.mul(2,3)    = {arith.mul(2, 3)}")       // 6

  print("arith.triple(4)   = {arith.triple(4)}")       // 12 (uses secret_factor)

  print("arith.scoped_total() = {arith.scoped_total()}") // 9

  print("arith.via_facade() = {arith.via_facade()}")   // 6 (crate-only)

  print("arith.public_value() = {arith.public_value()}") // 7 (public)

  print("absolute(-7)      = {absolute(-7)}")          // 7

  print("sign(-9)          = {sign(-9)}")              // -1

}