E3033

Error · Type

E3033 — A comptime block the evaluator could not finish. The block runs during compilation and leaves nothing behind, so one that cannot be run has no meaning — and used to be emitted as ordinary run-time code, which hid the fact entirely.

What the compiler reports

Error[E3033]{{.*}}writes to 'for_outer'

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 the Apache License 2.0 with LLVM Exceptions.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//

fn main() -> i32 {
  let mut for_outer : i32 = 0i32;
  let value = comptime {
    for i in 0i32..2i32 {
      for_outer = i;
    }
    7i32
  };
  return value;
}

From tests/frontend/fail/comptime_bounded_for_outer_write.vx, which asserts this diagnostic on every commit.

A tour of VxThe chapter covering the rule this code enforces. All diagnosticsEvery code the compiler can emit, grouped by stage. E3032A chain of generic instantiations that does not end — f<N - 1>() whose base case is never reached. Reported here rather than left to run out of stack, which gave no file, no line and no message. E3034A comptime block inside another one. The outer block already runs at compile time, so the inner one asks for nothing extra, and nesting them is what made a block's value depend on evaluating a closure defined inside another block.

E3033

What the compiler reports

A program that triggers it

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