use crate::rustc::hir::{Expr, ExprKind, MutMutable, QPath};
use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
use crate::rustc::{declare_tool_lint, lint_array};
-use crate::utils::{match_def_path, match_qpath, match_type, opt_def_id, paths, snippet, span_lint_and_sugg};
+use crate::utils::{match_def_path, match_qpath, opt_def_id, paths, snippet, span_lint_and_sugg};
use if_chain::if_chain;
/// **What it does:** Checks for `mem::replace()` on an `Option` with
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MemReplace {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
if_chain! {
+ // Check that `expr` is a call to `mem::replace()`
if let ExprKind::Call(ref func, ref func_args) = expr.node;
if func_args.len() == 2;
if let ExprKind::Path(ref func_qpath) = func.node;
if let Some(def_id) = opt_def_id(cx.tables.qpath_def(func_qpath, func.hir_id));
if match_def_path(cx.tcx, def_id, &paths::MEM_REPLACE);
- if let ExprKind::AddrOf(MutMutable, ref replaced) = func_args[0].node;
- if match_type(cx, cx.tables.expr_ty(replaced), &paths::OPTION);
+
+ // Check that second argument is `Option::None`
if let ExprKind::Path(ref replacement_qpath) = func_args[1].node;
if match_qpath(replacement_qpath, &paths::OPTION_NONE);
- if let ExprKind::Path(QPath::Resolved(None, ref replaced_path)) = replaced.node;
+
then {
- let sugg = format!("{}.take()", snippet(cx, replaced_path.span, ""));
+ // Since this is a late pass (already type-checked),
+ // and we already know that the second argument is an
+ // `Option`, we do not need to check if the first
+ // argument's type. All that's left is to get
+ // replacee's path.
+ let replaced_path = match func_args[0].node {
+ ExprKind::AddrOf(MutMutable, ref replaced) => {
+ if let ExprKind::Path(QPath::Resolved(None, ref replaced_path)) = replaced.node {
+ replaced_path
+ } else {
+ return
+ }
+ },
+ ExprKind::Path(QPath::Resolved(None, ref replaced_path)) => replaced_path,
+ _ => return,
+ };
+
span_lint_and_sugg(
cx,
MEM_REPLACE_OPTION_WITH_NONE,
expr.span,
"replacing an `Option` with `None`",
"consider `Option::take()` instead",
- sugg
+ format!("{}.take()", snippet(cx, replaced_path.span, ""))
);
}
}