You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: formatting.rs
    path of file: ./repos/rust-clippy/clippy_lints/src
    
    the code of the file until where you have to start completion: use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_note};
use clippy_utils::is_span_if;
use clippy_utils::source::snippet_opt;
use rustc_ast::ast::{BinOpKind, Block, Expr, ExprKind, StmtKind};
use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
use rustc_middle::lint::in_external_macro;
use rustc_session::declare_lint_pass;
use rustc_span::Span;

declare_clippy_lint! {
    /// ### What it does
    /// Checks for usage of the non-existent `=*`, `=!` and `=-`
    /// operators.
    ///
    /// ### Why is this bad?
    /// This is either a typo of `*=`, `!=` or `-=` or
    /// confusin
    
fn check_assign(cx: &EarlyContext<'_>, expr: &Expr) {
    if let ExprKind::Assign(ref lhs, ref rhs, _) = expr.kind {
        if !lhs.span.from_expansion() && !rhs.span.from_expansion() {
            let eq_span = lhs.span.between(rhs.span);
            if let ExprKind::Unary(op, ref sub_rhs) = rhs.kind {
                if let Some(eq_snippet) = snippet_opt(cx, eq_span) {
                    let op = op.as_str();
                    let eqop_span = lhs.span.between(sub_rhs.span);
                    if eq_snippet.ends_with('=') {
                        span_lint_and_note(
                            cx,
                            SUSPICIOUS_ASSIGNMENT_FORMATTING,
                            eqop_span,
                            &format!(
                                "this looks like you are trying to use `.. {op}= ..`, but you \
                                 really are doing `.. = ({op} ..)`"
                            ),
                            None,
                            &format!("to remove this lint, use either `{op}=` or `= {op}`"),
                        );
                    }
                }
            }
        }
    }
}