W1005

Warning

W1005 — A let that reuses a name already declared in the same block, so the first value can no longer be named.

What the compiler reports

Warning[W1005] at {{.*}}warning_for_a_name_declared_twice_in_one_block.vx:21:3: `x` is already a parameter of this function
Warning[W1005] at {{.*}}warning_for_a_name_declared_twice_in_one_block.vx:27:3: `total` is already declared in this block

The fragments the test suite holds the compiler to. An ellipsis marks text the test does not constrain; the emitted message also carries a source location.

A program that triggers it

//
// Part of the Vx Project, under the Apache License v2.0 with LLVM Exceptions.
// See LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//
// W1005 warns when a `let` reuses a parameter's name in a function's body, or a name declared
// earlier in its own block. An `if`, loop or `match` arm body may reuse an outer name, its loop
// variable or a pattern's name; `_` names never warn, and neither does a lone tuple `let`.

// COUNT-COUNT-2: Warning[W1005]
// COUNT-NOT: Warning[W1005]

fn add_one(x : i32) -> i32 {
  let x = x + 1;
  return x;
}

fn main() -> i32 {
  let total : i32 = 1;
  let total = total + 1;
  let _ignored = 1;
  let _ignored = 2;
  let (a, b) = (3, 4);
  if total > 0 {
    let total = a;
    print(total);
  }
  for i in 0..2 {
    let i = i + b;
    let total = i;
    print(total);
  }
  match (a, b) {
    (0, _) => {
      print(0);
    }, (p, q) => {
      let p = p + q;
      print(p);
    }
  }
  return add_one(total);
}

From tests/frontend/pass/warning_for_a_name_declared_twice_in_one_block.vx, which asserts this diagnostic on every commit.

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