allocator-first-param

Style

What This Rule Does

Checks that functions taking allocators as parameters have the allocator as the first parameter. This conforms to common Zig conventions.

Rule Details

This rule looks for functions take an Allocator parameter and reports a violation if

• it is not the first parameter, or
• there is a self parameter, and the allocator does not immediately follow it.

Parameters are considered to be an allocator if

• the are named allocator, alloc, gpa, or arena, or one of those with leading/trailing underscores,
• their type ends with Allocator

Parameters are considered to be a self parameter if

• they are named self, this, or one of those with leading/trailing underscores.
• their type is @This(), *@This(), etc.
• their type is a Capitalized and the function is within the definition of a similarly named container (e.g. a struct).

Examples

Examples of incorrect code for this rule:

fn foo(x: u32, allocator: Allocator) !*u32 {
  const heap_x = try allocator.create(u32);
  heap_x.* = x;
  return heap_x;
}

Examples of correct code for this rule:

fn foo(allocator: Allocator, x: u32) !*u32 {
  const heap_x = try allocator.create(u32);
  heap_x.* = x;
  return heap_x;
}
const Foo = struct {
  list: std.ArrayListUnmanaged(u32) = .{},
  // when writing methods, `self` must be the first parameter
  pub fn expandCapacity(self: *Foo, allocator: Allocator, new_len: usize) !void {
    try self.list.ensureTotalCapacity(allocator, new_len);
  }
};

Configuration

This rule accepts the following options:

• ignore: array