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use rustc::lint::*;
use rustc::hir::*;
use utils::{paths, method_chain_args, span_help_and_lint, match_type, snippet};
declare_lint! {
pub IF_LET_SOME_RESULT,
Warn,
"usage of `ok()` in `if let Some(pat)` statements is unnecessary, match on `Ok(pat)` instead"
}
#[derive(Copy, Clone)]
pub struct Pass;
impl LintPass for Pass {
fn get_lints(&self) -> LintArray {
lint_array!(IF_LET_SOME_RESULT)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
if_let_chain! {[
let ExprMatch(ref op, ref body, ref source) = expr.node,
let MatchSource::IfLetDesugar { .. } = *source,
let ExprMethodCall(_, _, ref result_types) = op.node,
let PatKind::TupleStruct(QPath::Resolved(_, ref x), ref y, _) = body[0].pats[0].node,
method_chain_args(op, &["ok"]).is_some()
], {
let is_result_type = match_type(cx, cx.tcx.tables().expr_ty(&result_types[0]), &paths::RESULT);
let some_expr_string = snippet(cx, y[0].span, "");
if print::to_string(print::NO_ANN, |s| s.print_path(x, false)) == "Some" && is_result_type {
span_help_and_lint(cx, IF_LET_SOME_RESULT, expr.span,
"Matching on `Some` with `ok()` is redundant",
&format!("Consider matching on `Ok({})` and removing the call to `ok` instead", some_expr_string));
}
}}
}
}