1 use super::utils::make_iterator_snippet;
2 use super::MANUAL_FLATTEN;
3 use clippy_utils::diagnostics::span_lint_and_then;
4 use clippy_utils::{is_lang_ctor, path_to_local_id};
5 use if_chain::if_chain;
6 use rustc_errors::Applicability;
7 use rustc_hir::LangItem::{OptionSome, ResultOk};
8 use rustc_hir::{Expr, ExprKind, MatchSource, Pat, PatKind, StmtKind};
9 use rustc_lint::LateContext;
11 use rustc_span::source_map::Span;
13 /// Check for unnecessary `if let` usage in a for loop where only the `Some` or `Ok` variant of the
14 /// iterator element is used.
15 pub(super) fn check<'tcx>(
16 cx: &LateContext<'tcx>,
22 if let ExprKind::Block(block, _) = body.kind {
23 // Ensure the `if let` statement is the only expression or statement in the for-loop
24 let inner_expr = if block.stmts.len() == 1 && block.expr.is_none() {
25 let match_stmt = &block.stmts[0];
26 if let StmtKind::Semi(inner_expr) = match_stmt.kind {
31 } else if block.stmts.is_empty() {
38 if let Some(inner_expr) = inner_expr;
39 if let ExprKind::Match(
40 match_expr, match_arms, MatchSource::IfLetDesugar{ contains_else_clause: false }
42 // Ensure match_expr in `if let` statement is the same as the pat from the for-loop
43 if let PatKind::Binding(_, pat_hir_id, _, _) = pat.kind;
44 if path_to_local_id(match_expr, pat_hir_id);
45 // Ensure the `if let` statement is for the `Some` variant of `Option` or the `Ok` variant of `Result`
46 if let PatKind::TupleStruct(ref qpath, _, _) = match_arms[0].pat.kind;
47 let some_ctor = is_lang_ctor(cx, qpath, OptionSome);
48 let ok_ctor = is_lang_ctor(cx, qpath, ResultOk);
49 if some_ctor || ok_ctor;
51 let if_let_type = if some_ctor { "Some" } else { "Ok" };
52 // Prepare the error message
53 let msg = format!("unnecessary `if let` since only the `{}` variant of the iterator element is used", if_let_type);
55 // Prepare the help message
56 let mut applicability = Applicability::MaybeIncorrect;
57 let arg_snippet = make_iterator_snippet(cx, arg, &mut applicability);
58 let copied = match cx.typeck_results().expr_ty(match_expr).kind() {
59 ty::Ref(_, inner, _) => match inner.kind() {
60 ty::Ref(..) => ".copied()",
72 let sugg = format!("{}{}.flatten()", arg_snippet, copied);
77 Applicability::MaybeIncorrect,
81 "...and remove the `if let` statement in the for loop",