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Diffstat (limited to 'src/tools/clippy/clippy_lints/src/matches/redundant_pattern_match.rs')
| -rw-r--r-- | src/tools/clippy/clippy_lints/src/matches/redundant_pattern_match.rs | 304 |
1 files changed, 304 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/matches/redundant_pattern_match.rs b/src/tools/clippy/clippy_lints/src/matches/redundant_pattern_match.rs new file mode 100644 index 000000000..8499e050a --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/matches/redundant_pattern_match.rs @@ -0,0 +1,304 @@ +use super::REDUNDANT_PATTERN_MATCHING; +use clippy_utils::diagnostics::span_lint_and_then; +use clippy_utils::source::snippet; +use clippy_utils::sugg::Sugg; +use clippy_utils::ty::needs_ordered_drop; +use clippy_utils::visitors::any_temporaries_need_ordered_drop; +use clippy_utils::{higher, is_lang_ctor, is_trait_method, match_def_path, paths}; +use if_chain::if_chain; +use rustc_ast::ast::LitKind; +use rustc_errors::Applicability; +use rustc_hir::LangItem::{OptionNone, PollPending}; +use rustc_hir::{Arm, Expr, ExprKind, Node, Pat, PatKind, QPath, UnOp}; +use rustc_lint::LateContext; +use rustc_middle::ty::{self, subst::GenericArgKind, DefIdTree, Ty}; +use rustc_span::sym; + +pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { + if let Some(higher::WhileLet { let_pat, let_expr, .. }) = higher::WhileLet::hir(expr) { + find_sugg_for_if_let(cx, expr, let_pat, let_expr, "while", false); + } +} + +pub(super) fn check_if_let<'tcx>( + cx: &LateContext<'tcx>, + expr: &'tcx Expr<'_>, + pat: &'tcx Pat<'_>, + scrutinee: &'tcx Expr<'_>, + has_else: bool, +) { + find_sugg_for_if_let(cx, expr, pat, scrutinee, "if", has_else); +} + +// Extract the generic arguments out of a type +fn try_get_generic_ty(ty: Ty<'_>, index: usize) -> Option<Ty<'_>> { + if_chain! { + if let ty::Adt(_, subs) = ty.kind(); + if let Some(sub) = subs.get(index); + if let GenericArgKind::Type(sub_ty) = sub.unpack(); + then { + Some(sub_ty) + } else { + None + } + } +} + +fn find_sugg_for_if_let<'tcx>( + cx: &LateContext<'tcx>, + expr: &'tcx Expr<'_>, + let_pat: &Pat<'_>, + let_expr: &'tcx Expr<'_>, + keyword: &'static str, + has_else: bool, +) { + // also look inside refs + // if we have &None for example, peel it so we can detect "if let None = x" + let check_pat = match let_pat.kind { + PatKind::Ref(inner, _mutability) => inner, + _ => let_pat, + }; + let op_ty = cx.typeck_results().expr_ty(let_expr); + // Determine which function should be used, and the type contained by the corresponding + // variant. + let (good_method, inner_ty) = match check_pat.kind { + PatKind::TupleStruct(ref qpath, [sub_pat], _) => { + if let PatKind::Wild = sub_pat.kind { + let res = cx.typeck_results().qpath_res(qpath, check_pat.hir_id); + let Some(id) = res.opt_def_id().map(|ctor_id| cx.tcx.parent(ctor_id)) else { return }; + let lang_items = cx.tcx.lang_items(); + if Some(id) == lang_items.result_ok_variant() { + ("is_ok()", try_get_generic_ty(op_ty, 0).unwrap_or(op_ty)) + } else if Some(id) == lang_items.result_err_variant() { + ("is_err()", try_get_generic_ty(op_ty, 1).unwrap_or(op_ty)) + } else if Some(id) == lang_items.option_some_variant() { + ("is_some()", op_ty) + } else if Some(id) == lang_items.poll_ready_variant() { + ("is_ready()", op_ty) + } else if match_def_path(cx, id, &paths::IPADDR_V4) { + ("is_ipv4()", op_ty) + } else if match_def_path(cx, id, &paths::IPADDR_V6) { + ("is_ipv6()", op_ty) + } else { + return; + } + } else { + return; + } + }, + PatKind::Path(ref path) => { + let method = if is_lang_ctor(cx, path, OptionNone) { + "is_none()" + } else if is_lang_ctor(cx, path, PollPending) { + "is_pending()" + } else { + return; + }; + // `None` and `Pending` don't have an inner type. + (method, cx.tcx.types.unit) + }, + _ => return, + }; + + // If this is the last expression in a block or there is an else clause then the whole + // type needs to be considered, not just the inner type of the branch being matched on. + // Note the last expression in a block is dropped after all local bindings. + let check_ty = if has_else + || (keyword == "if" && matches!(cx.tcx.hir().parent_iter(expr.hir_id).next(), Some((_, Node::Block(..))))) + { + op_ty + } else { + inner_ty + }; + + // All temporaries created in the scrutinee expression are dropped at the same time as the + // scrutinee would be, so they have to be considered as well. + // e.g. in `if let Some(x) = foo.lock().unwrap().baz.as_ref() { .. }` the lock will be held + // for the duration if body. + let needs_drop = needs_ordered_drop(cx, check_ty) || any_temporaries_need_ordered_drop(cx, let_expr); + + // check that `while_let_on_iterator` lint does not trigger + if_chain! { + if keyword == "while"; + if let ExprKind::MethodCall(method_path, _, _) = let_expr.kind; + if method_path.ident.name == sym::next; + if is_trait_method(cx, let_expr, sym::Iterator); + then { + return; + } + } + + let result_expr = match &let_expr.kind { + ExprKind::AddrOf(_, _, borrowed) => borrowed, + ExprKind::Unary(UnOp::Deref, deref) => deref, + _ => let_expr, + }; + + span_lint_and_then( + cx, + REDUNDANT_PATTERN_MATCHING, + let_pat.span, + &format!("redundant pattern matching, consider using `{}`", good_method), + |diag| { + // if/while let ... = ... { ... } + // ^^^^^^^^^^^^^^^^^^^^^^^^^^^ + let expr_span = expr.span; + + // if/while let ... = ... { ... } + // ^^^ + let op_span = result_expr.span.source_callsite(); + + // if/while let ... = ... { ... } + // ^^^^^^^^^^^^^^^^^^^ + let span = expr_span.until(op_span.shrink_to_hi()); + + let app = if needs_drop { + Applicability::MaybeIncorrect + } else { + Applicability::MachineApplicable + }; + + let sugg = Sugg::hir_with_macro_callsite(cx, result_expr, "_") + .maybe_par() + .to_string(); + + diag.span_suggestion(span, "try this", format!("{} {}.{}", keyword, sugg, good_method), app); + + if needs_drop { + diag.note("this will change drop order of the result, as well as all temporaries"); + diag.note("add `#[allow(clippy::redundant_pattern_matching)]` if this is important"); + } + }, + ); +} + +pub(super) fn check_match<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, op: &Expr<'_>, arms: &[Arm<'_>]) { + if arms.len() == 2 { + let node_pair = (&arms[0].pat.kind, &arms[1].pat.kind); + + let found_good_method = match node_pair { + ( + PatKind::TupleStruct(ref path_left, patterns_left, _), + PatKind::TupleStruct(ref path_right, patterns_right, _), + ) if patterns_left.len() == 1 && patterns_right.len() == 1 => { + if let (PatKind::Wild, PatKind::Wild) = (&patterns_left[0].kind, &patterns_right[0].kind) { + find_good_method_for_match( + cx, + arms, + path_left, + path_right, + &paths::RESULT_OK, + &paths::RESULT_ERR, + "is_ok()", + "is_err()", + ) + .or_else(|| { + find_good_method_for_match( + cx, + arms, + path_left, + path_right, + &paths::IPADDR_V4, + &paths::IPADDR_V6, + "is_ipv4()", + "is_ipv6()", + ) + }) + } else { + None + } + }, + (PatKind::TupleStruct(ref path_left, patterns, _), PatKind::Path(ref path_right)) + | (PatKind::Path(ref path_left), PatKind::TupleStruct(ref path_right, patterns, _)) + if patterns.len() == 1 => + { + if let PatKind::Wild = patterns[0].kind { + find_good_method_for_match( + cx, + arms, + path_left, + path_right, + &paths::OPTION_SOME, + &paths::OPTION_NONE, + "is_some()", + "is_none()", + ) + .or_else(|| { + find_good_method_for_match( + cx, + arms, + path_left, + path_right, + &paths::POLL_READY, + &paths::POLL_PENDING, + "is_ready()", + "is_pending()", + ) + }) + } else { + None + } + }, + _ => None, + }; + + if let Some(good_method) = found_good_method { + let span = expr.span.to(op.span); + let result_expr = match &op.kind { + ExprKind::AddrOf(_, _, borrowed) => borrowed, + _ => op, + }; + span_lint_and_then( + cx, + REDUNDANT_PATTERN_MATCHING, + expr.span, + &format!("redundant pattern matching, consider using `{}`", good_method), + |diag| { + diag.span_suggestion( + span, + "try this", + format!("{}.{}", snippet(cx, result_expr.span, "_"), good_method), + Applicability::MaybeIncorrect, // snippet + ); + }, + ); + } + } +} + +#[expect(clippy::too_many_arguments)] +fn find_good_method_for_match<'a>( + cx: &LateContext<'_>, + arms: &[Arm<'_>], + path_left: &QPath<'_>, + path_right: &QPath<'_>, + expected_left: &[&str], + expected_right: &[&str], + should_be_left: &'a str, + should_be_right: &'a str, +) -> Option<&'a str> { + let left_id = cx + .typeck_results() + .qpath_res(path_left, arms[0].pat.hir_id) + .opt_def_id()?; + let right_id = cx + .typeck_results() + .qpath_res(path_right, arms[1].pat.hir_id) + .opt_def_id()?; + let body_node_pair = if match_def_path(cx, left_id, expected_left) && match_def_path(cx, right_id, expected_right) { + (&arms[0].body.kind, &arms[1].body.kind) + } else if match_def_path(cx, right_id, expected_left) && match_def_path(cx, right_id, expected_right) { + (&arms[1].body.kind, &arms[0].body.kind) + } else { + return None; + }; + + match body_node_pair { + (ExprKind::Lit(ref lit_left), ExprKind::Lit(ref lit_right)) => match (&lit_left.node, &lit_right.node) { + (LitKind::Bool(true), LitKind::Bool(false)) => Some(should_be_left), + (LitKind::Bool(false), LitKind::Bool(true)) => Some(should_be_right), + _ => None, + }, + _ => None, + } +} |