unused-decls

Correctness

This rule is enabled as a warning by default.

This rule has a dangerous fix available

What This Rule Does

Disallows container-scoped variables that are declared but never used. Note that top-level declarations are included.

The Zig compiler checks for unused parameters, payloads bound by if, catch, etc, and const/var declaration within functions. However, variables and functions declared in container scopes are not given the same treatment. This rule handles those cases.

warning

ZLint's semantic analyzer does not yet record references to variables on member access expressions (e.g. bar on foo.bar). It also does not handle method calls correctly. Until these features are added, only top-level const variable declarations are checked.

Examples

Examples of incorrect code for this rule:

// `std` used, but `Allocator` is not.
const std = @import("std");
const Allocator = std.mem.Allocator;

// Variables available to other code, either via `export` or `pub`, are not
// reported.
pub const x = 1;
export fn foo(x: u32) void {}

// `extern` functions are not reported
extern fn bar(a: i32) void;

Examples of correct code for this rule:

// Discarded variables are considered "used".
const x = 1;
_ = x;

// non-container scoped variables are allowed by this rule but banned by the
// compiler. `x`, `y`, and `z` are ignored by this rule.
pub fn foo(x: u32) void {
  const y = true;
  var z: u32 = 1;
}

Configuration

This rule has no configuration.