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Auto merge of #8400 - Jarcho:split_matches, r=Manishearth

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Split matches

Part of #6680

changelog: None
This commit is contained in:
bors 2022-02-07 20:10:07 +00:00
commit 2590701b2a
16 changed files with 2548 additions and 2445 deletions
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2445
clippy_lints/src/matches.rs
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44
clippy_lints/src/matches/infalliable_detructuring_match.rs Normal file
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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::{path_to_local_id, peel_blocks, strip_pat_refs};
use rustc_errors::Applicability;
use rustc_hir::{ExprKind, Local, MatchSource, PatKind, QPath};
use rustc_lint::LateContext;
use super::INFALLIBLE_DESTRUCTURING_MATCH;
pub(crate) fn check(cx: &LateContext<'_>, local: &Local<'_>) -> bool {
if_chain! {
if !local.span.from_expansion();
if let Some(expr) = local.init;
if let ExprKind::Match(target, arms, MatchSource::Normal) = expr.kind;
if arms.len() == 1 && arms[0].guard.is_none();
if let PatKind::TupleStruct(
QPath::Resolved(None, variant_name), args, _) = arms[0].pat.kind;
if args.len() == 1;
if let PatKind::Binding(_, arg, ..) = strip_pat_refs(&args[0]).kind;
let body = peel_blocks(arms[0].body);
if path_to_local_id(body, arg);
then {
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
INFALLIBLE_DESTRUCTURING_MATCH,
local.span,
"you seem to be trying to use `match` to destructure a single infallible pattern. \
Consider using `let`",
"try this",
format!(
"let {}({}) = {};",
snippet_with_applicability(cx, variant_name.span, "..", &mut applicability),
snippet_with_applicability(cx, local.pat.span, "..", &mut applicability),
snippet_with_applicability(cx, target.span, "..", &mut applicability),
),
applicability,
);
return true;
}
}
false
}

85
clippy_lints/src/matches/match_as_ref.rs Normal file
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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::{is_lang_ctor, peel_blocks};
use rustc_errors::Applicability;
use rustc_hir::{Arm, BindingAnnotation, Expr, ExprKind, LangItem, PatKind, QPath};
use rustc_lint::LateContext;
use rustc_middle::ty;
use super::MATCH_AS_REF;
pub(crate) fn check(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
let arm_ref: Option<BindingAnnotation> = if is_none_arm(cx, &arms[0]) {
is_ref_some_arm(cx, &arms[1])
} else if is_none_arm(cx, &arms[1]) {
is_ref_some_arm(cx, &arms[0])
} else {
None
};
if let Some(rb) = arm_ref {
let suggestion = if rb == BindingAnnotation::Ref {
"as_ref"
} else {
"as_mut"
};
let output_ty = cx.typeck_results().expr_ty(expr);
let input_ty = cx.typeck_results().expr_ty(ex);
let cast = if_chain! {
if let ty::Adt(_, substs) = input_ty.kind();
let input_ty = substs.type_at(0);
if let ty::Adt(_, substs) = output_ty.kind();
let output_ty = substs.type_at(0);
if let ty::Ref(_, output_ty, _) = *output_ty.kind();
if input_ty != output_ty;
then {
".map(|x| x as _)"
} else {
""
}
};
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
MATCH_AS_REF,
expr.span,
&format!("use `{}()` instead", suggestion),
"try this",
format!(
"{}.{}(){}",
snippet_with_applicability(cx, ex.span, "_", &mut applicability),
suggestion,
cast,
),
applicability,
);
}
}
}
// Checks if arm has the form `None => None`
fn is_none_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> bool {
matches!(arm.pat.kind, PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, LangItem::OptionNone))
}
// Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
fn is_ref_some_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> Option<BindingAnnotation> {
if_chain! {
if let PatKind::TupleStruct(ref qpath, [first_pat, ..], _) = arm.pat.kind;
if is_lang_ctor(cx, qpath, LangItem::OptionSome);
if let PatKind::Binding(rb, .., ident, _) = first_pat.kind;
if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
if let ExprKind::Call(e, args) = peel_blocks(arm.body).kind;
if let ExprKind::Path(ref some_path) = e.kind;
if is_lang_ctor(cx, some_path, LangItem::OptionSome) && args.len() == 1;
if let ExprKind::Path(QPath::Resolved(_, path2)) = args[0].kind;
if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
then {
return Some(rb)
}
}
None
}

75
clippy_lints/src/matches/match_bool.rs Normal file
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use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::is_unit_expr;
use clippy_utils::source::{expr_block, snippet};
use clippy_utils::sugg::Sugg;
use rustc_ast::LitKind;
use rustc_errors::Applicability;
use rustc_hir::{Arm, Expr, ExprKind, PatKind};
use rustc_lint::LateContext;
use rustc_middle::ty;
use super::MATCH_BOOL;
pub(crate) fn check(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
// Type of expression is `bool`.
if *cx.typeck_results().expr_ty(ex).kind() == ty::Bool {
span_lint_and_then(
cx,
MATCH_BOOL,
expr.span,
"you seem to be trying to match on a boolean expression",
move |diag| {
if arms.len() == 2 {
// no guards
let exprs = if let PatKind::Lit(arm_bool) = arms[0].pat.kind {
if let ExprKind::Lit(ref lit) = arm_bool.kind {
match lit.node {
LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
_ => None,
}
} else {
None
}
} else {
None
};
if let Some((true_expr, false_expr)) = exprs {
let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
(false, false) => Some(format!(
"if {} {} else {}",
snippet(cx, ex.span, "b"),
expr_block(cx, true_expr, None, "..", Some(expr.span)),
expr_block(cx, false_expr, None, "..", Some(expr.span))
)),
(false, true) => Some(format!(
"if {} {}",
snippet(cx, ex.span, "b"),
expr_block(cx, true_expr, None, "..", Some(expr.span))
)),
(true, false) => {
let test = Sugg::hir(cx, ex, "..");
Some(format!(
"if {} {}",
!test,
expr_block(cx, false_expr, None, "..", Some(expr.span))
))
},
(true, true) => None,
};
if let Some(sugg) = sugg {
diag.span_suggestion(
expr.span,
"consider using an `if`/`else` expression",
sugg,
Applicability::HasPlaceholders,
);
}
}
}
},
);
}
}

166
clippy_lints/src/matches/match_like_matches.rs Normal file
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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::{higher, is_wild};
use rustc_ast::{Attribute, LitKind};
use rustc_errors::Applicability;
use rustc_hir::{BorrowKind, Expr, ExprKind, Guard, MatchSource, Pat};
use rustc_lint::LateContext;
use rustc_middle::ty;
use rustc_span::source_map::Spanned;
use super::MATCH_LIKE_MATCHES_MACRO;
/// Lint a `match` or `if let .. { .. } else { .. }` expr that could be replaced by `matches!`
pub(crate) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
if let Some(higher::IfLet {
let_pat,
let_expr,
if_then,
if_else: Some(if_else),
}) = higher::IfLet::hir(cx, expr)
{
return find_matches_sugg(
cx,
let_expr,
IntoIterator::into_iter([(&[][..], Some(let_pat), if_then, None), (&[][..], None, if_else, None)]),
expr,
true,
);
}
if let ExprKind::Match(scrut, arms, MatchSource::Normal) = expr.kind {
return find_matches_sugg(
cx,
scrut,
arms.iter().map(|arm| {
(
cx.tcx.hir().attrs(arm.hir_id),
Some(arm.pat),
arm.body,
arm.guard.as_ref(),
)
}),
expr,
false,
);
}
false
}
/// Lint a `match` or `if let` for replacement by `matches!`
fn find_matches_sugg<'a, 'b, I>(
cx: &LateContext<'_>,
ex: &Expr<'_>,
mut iter: I,
expr: &Expr<'_>,
is_if_let: bool,
) -> bool
where
'b: 'a,
I: Clone
+ DoubleEndedIterator
+ ExactSizeIterator
+ Iterator<
Item = (
&'a [Attribute],
Option<&'a Pat<'b>>,
&'a Expr<'b>,
Option<&'a Guard<'b>>,
),
>,
{
if_chain! {
if iter.len() >= 2;
if cx.typeck_results().expr_ty(expr).is_bool();
if let Some((_, last_pat_opt, last_expr, _)) = iter.next_back();
let iter_without_last = iter.clone();
if let Some((first_attrs, _, first_expr, first_guard)) = iter.next();
if let Some(b0) = find_bool_lit(&first_expr.kind, is_if_let);
if let Some(b1) = find_bool_lit(&last_expr.kind, is_if_let);
if b0 != b1;
if first_guard.is_none() || iter.len() == 0;
if first_attrs.is_empty();
if iter
.all(|arm| {
find_bool_lit(&arm.2.kind, is_if_let).map_or(false, |b| b == b0) && arm.3.is_none() && arm.0.is_empty()
});
then {
if let Some(last_pat) = last_pat_opt {
if !is_wild(last_pat) {
return false;
}
}
// The suggestion may be incorrect, because some arms can have `cfg` attributes
// evaluated into `false` and so such arms will be stripped before.
let mut applicability = Applicability::MaybeIncorrect;
let pat = {
use itertools::Itertools as _;
iter_without_last
.filter_map(|arm| {
let pat_span = arm.1?.span;
Some(snippet_with_applicability(cx, pat_span, "..", &mut applicability))
})
.join(" | ")
};
let pat_and_guard = if let Some(Guard::If(g)) = first_guard {
format!("{} if {}", pat, snippet_with_applicability(cx, g.span, "..", &mut applicability))
} else {
pat
};
// strip potential borrows (#6503), but only if the type is a reference
let mut ex_new = ex;
if let ExprKind::AddrOf(BorrowKind::Ref, .., ex_inner) = ex.kind {
if let ty::Ref(..) = cx.typeck_results().expr_ty(ex_inner).kind() {
ex_new = ex_inner;
}
};
span_lint_and_sugg(
cx,
MATCH_LIKE_MATCHES_MACRO,
expr.span,
&format!("{} expression looks like `matches!` macro", if is_if_let { "if let .. else" } else { "match" }),
"try this",
format!(
"{}matches!({}, {})",
if b0 { "" } else { "!" },
snippet_with_applicability(cx, ex_new.span, "..", &mut applicability),
pat_and_guard,
),
applicability,
);
true
} else {
false
}
}
}
/// Extract a `bool` or `{ bool }`
fn find_bool_lit(ex: &ExprKind<'_>, is_if_let: bool) -> Option<bool> {
match ex {
ExprKind::Lit(Spanned {
node: LitKind::Bool(b), ..
}) => Some(*b),
ExprKind::Block(
rustc_hir::Block {
stmts: &[],
expr: Some(exp),
..
},
_,
) if is_if_let => {
if let ExprKind::Lit(Spanned {
node: LitKind::Bool(b), ..
}) = exp.kind
{
Some(b)
} else {
None
}
},
_ => None,
}
}

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clippy_lints/src/matches/match_ref_pats.rs Normal file
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use clippy_utils::diagnostics::{multispan_sugg, span_lint_and_then};
use clippy_utils::source::snippet;
use clippy_utils::sugg::Sugg;
use core::iter::once;
use rustc_hir::{BorrowKind, Expr, ExprKind, Mutability, Pat, PatKind};
use rustc_lint::LateContext;
use super::MATCH_REF_PATS;
pub(crate) fn check<'a, 'b, I>(cx: &LateContext<'_>, ex: &Expr<'_>, pats: I, expr: &Expr<'_>)
where
'b: 'a,
I: Clone + Iterator<Item = &'a Pat<'b>>,
{
if !has_multiple_ref_pats(pats.clone()) {
return;
}
let (first_sugg, msg, title);
let span = ex.span.source_callsite();
if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner) = ex.kind {
first_sugg = once((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
msg = "try";
title = "you don't need to add `&` to both the expression and the patterns";
} else {
first_sugg = once((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
msg = "instead of prefixing all patterns with `&`, you can dereference the expression";
title = "you don't need to add `&` to all patterns";
}
let remaining_suggs = pats.filter_map(|pat| {
if let PatKind::Ref(refp, _) = pat.kind {
Some((pat.span, snippet(cx, refp.span, "..").to_string()))
} else {
None
}
});
span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| {
if !expr.span.from_expansion() {
multispan_sugg(diag, msg, first_sugg.chain(remaining_suggs));
}
});
}
fn has_multiple_ref_pats<'a, 'b, I>(pats: I) -> bool
where
'b: 'a,
I: Iterator<Item = &'a Pat<'b>>,
{
let mut ref_count = 0;
for opt in pats.map(|pat| match pat.kind {
PatKind::Ref(..) => Some(true), // &-patterns
PatKind::Wild => Some(false), // an "anything" wildcard is also fine
_ => None, // any other pattern is not fine
}) {
if let Some(inner) = opt {
if inner {
ref_count += 1;
}
} else {
return false;
}
}
ref_count > 1
}

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clippy_lints/src/matches/match_same_arms.rs Normal file
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use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::source::snippet;
use clippy_utils::{path_to_local, search_same, SpanlessEq, SpanlessHash};
use rustc_hir::{Arm, Expr, ExprKind, HirId, HirIdMap, HirIdSet, MatchSource, Pat, PatKind};
use rustc_lint::LateContext;
use rustc_middle::ty::TyS;
use std::collections::hash_map::Entry;
use super::MATCH_SAME_ARMS;
pub(crate) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) {
if let ExprKind::Match(_, arms, MatchSource::Normal) = expr.kind {
let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 {
let mut h = SpanlessHash::new(cx);
h.hash_expr(arm.body);
h.finish()
};
let eq = |&(lindex, lhs): &(usize, &Arm<'_>), &(rindex, rhs): &(usize, &Arm<'_>)| -> bool {
let min_index = usize::min(lindex, rindex);
let max_index = usize::max(lindex, rindex);
let mut local_map: HirIdMap<HirId> = HirIdMap::default();
let eq_fallback = |a: &Expr<'_>, b: &Expr<'_>| {
if_chain! {
if let Some(a_id) = path_to_local(a);
if let Some(b_id) = path_to_local(b);
let entry = match local_map.entry(a_id) {
Entry::Vacant(entry) => entry,
// check if using the same bindings as before
Entry::Occupied(entry) => return *entry.get() == b_id,
};
// the names technically don't have to match; this makes the lint more conservative
if cx.tcx.hir().name(a_id) == cx.tcx.hir().name(b_id);
if TyS::same_type(cx.typeck_results().expr_ty(a), cx.typeck_results().expr_ty(b));
if pat_contains_local(lhs.pat, a_id);
if pat_contains_local(rhs.pat, b_id);
then {
entry.insert(b_id);
true
} else {
false
}
}
};
// Arms with a guard are ignored, those can’t always be merged together
// This is also the case for arms in-between each there is an arm with a guard
(min_index..=max_index).all(|index| arms[index].guard.is_none())
&& SpanlessEq::new(cx)
.expr_fallback(eq_fallback)
.eq_expr(lhs.body, rhs.body)
// these checks could be removed to allow unused bindings
&& bindings_eq(lhs.pat, local_map.keys().copied().collect())
&& bindings_eq(rhs.pat, local_map.values().copied().collect())
};
let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect();
for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) {
span_lint_and_then(
cx,
MATCH_SAME_ARMS,
j.body.span,
"this `match` has identical arm bodies",
|diag| {
diag.span_note(i.body.span, "same as this");
// Note: this does not use `span_suggestion` on purpose:
// there is no clean way
// to remove the other arm. Building a span and suggest to replace it to ""
// makes an even more confusing error message. Also in order not to make up a
// span for the whole pattern, the suggestion is only shown when there is only
// one pattern. The user should know about `|` if they are already using it…
let lhs = snippet(cx, i.pat.span, "<pat1>");
let rhs = snippet(cx, j.pat.span, "<pat2>");
if let PatKind::Wild = j.pat.kind {
// if the last arm is _, then i could be integrated into _
// note that i.pat cannot be _, because that would mean that we're
// hiding all the subsequent arms, and rust won't compile
diag.span_note(
i.body.span,
&format!(
"`{}` has the same arm body as the `_` wildcard, consider removing it",
lhs
),
);
} else {
diag.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs,))
.help("...or consider changing the match arm bodies");
}
},
);
}
}
}
fn pat_contains_local(pat: &Pat<'_>, id: HirId) -> bool {
let mut result = false;
pat.walk_short(|p| {
result |= matches!(p.kind, PatKind::Binding(_, binding_id, ..) if binding_id == id);
!result
});
result
}
/// Returns true if all the bindings in the `Pat` are in `ids` and vice versa
fn bindings_eq(pat: &Pat<'_>, mut ids: HirIdSet) -> bool {
let mut result = true;
pat.each_binding_or_first(&mut |_, id, _, _| result &= ids.remove(&id));
result && ids.is_empty()
}

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clippy_lints/src/matches/match_single_binding.rs Normal file
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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::{indent_of, snippet_block, snippet_opt, snippet_with_applicability};
use clippy_utils::sugg::Sugg;
use clippy_utils::{get_parent_expr, is_refutable, peel_blocks};
use rustc_errors::Applicability;
use rustc_hir::{Arm, Expr, ExprKind, Local, Node, PatKind};
use rustc_lint::LateContext;
use super::MATCH_SINGLE_BINDING;
#[allow(clippy::too_many_lines)]
pub(crate) fn check<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
if expr.span.from_expansion() || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
return;
}
// HACK:
// This is a hack to deal with arms that are excluded by macros like `#[cfg]`. It is only used here
// to prevent false positives as there is currently no better way to detect if code was excluded by
// a macro. See PR #6435
if_chain! {
if let Some(match_snippet) = snippet_opt(cx, expr.span);
if let Some(arm_snippet) = snippet_opt(cx, arms[0].span);
if let Some(ex_snippet) = snippet_opt(cx, ex.span);
let rest_snippet = match_snippet.replace(&arm_snippet, "").replace(&ex_snippet, "");
if rest_snippet.contains("=>");
then {
// The code it self contains another thick arrow "=>"
// -> Either another arm or a comment
return;
}
}
let matched_vars = ex.span;
let bind_names = arms[0].pat.span;
let match_body = peel_blocks(arms[0].body);
let mut snippet_body = if match_body.span.from_expansion() {
Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
} else {
snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
};
// Do we need to add ';' to suggestion ?
match match_body.kind {
ExprKind::Block(block, _) => {
// macro + expr_ty(body) == ()
if block.span.from_expansion() && cx.typeck_results().expr_ty(match_body).is_unit() {
snippet_body.push(';');
}
},
_ => {
// expr_ty(body) == ()
if cx.typeck_results().expr_ty(match_body).is_unit() {
snippet_body.push(';');
}
},
}
let mut applicability = Applicability::MaybeIncorrect;
match arms[0].pat.kind {
PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
// If this match is in a local (`let`) stmt
let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
(
parent_let_node.span,
format!(
"let {} = {};\n{}let {} = {};",
snippet_with_applicability(cx, bind_names, "..", &mut applicability),
snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
" ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
snippet_body
),
)
} else {
// If we are in closure, we need curly braces around suggestion
let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0));
let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string());
if let Some(parent_expr) = get_parent_expr(cx, expr) {
if let ExprKind::Closure(..) = parent_expr.kind {
cbrace_end = format!("\n{}}}", indent);
// Fix body indent due to the closure
indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
cbrace_start = format!("{{\n{}", indent);
}
}
// If the parent is already an arm, and the body is another match statement,
// we need curly braces around suggestion
let parent_node_id = cx.tcx.hir().get_parent_node(expr.hir_id);
if let Node::Arm(arm) = &cx.tcx.hir().get(parent_node_id) {
if let ExprKind::Match(..) = arm.body.kind {
cbrace_end = format!("\n{}}}", indent);
// Fix body indent due to the match
indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
cbrace_start = format!("{{\n{}", indent);
}
}
(
expr.span,
format!(
"{}let {} = {};\n{}{}{}",
cbrace_start,
snippet_with_applicability(cx, bind_names, "..", &mut applicability),
snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
indent,
snippet_body,
cbrace_end
),
)
};
span_lint_and_sugg(
cx,
MATCH_SINGLE_BINDING,
target_span,
"this match could be written as a `let` statement",
"consider using `let` statement",
sugg,
applicability,
);
},
PatKind::Wild => {
if ex.can_have_side_effects() {
let indent = " ".repeat(indent_of(cx, expr.span).unwrap_or(0));
let sugg = format!(
"{};\n{}{}",
snippet_with_applicability(cx, ex.span, "..", &mut applicability),
indent,
snippet_body
);
span_lint_and_sugg(
cx,
MATCH_SINGLE_BINDING,
expr.span,
"this match could be replaced by its scrutinee and body",
"consider using the scrutinee and body instead",
sugg,
applicability,
);
} else {
span_lint_and_sugg(
cx,
MATCH_SINGLE_BINDING,
expr.span,
"this match could be replaced by its body itself",
"consider using the match body instead",
snippet_body,
Applicability::MachineApplicable,
);
}
},
_ => (),
}
}
/// Returns true if the `ex` match expression is in a local (`let`) statement
fn opt_parent_let<'a>(cx: &LateContext<'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
let map = &cx.tcx.hir();
if_chain! {
if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
then {
return Some(parent_let_expr);
}
}
None
}

198
clippy_lints/src/matches/match_wild_enum.rs Normal file
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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::{is_refutable, peel_hir_pat_refs, recurse_or_patterns};
use rustc_errors::Applicability;
use rustc_hir::def::{CtorKind, DefKind, Res};
use rustc_hir::{Arm, Expr, PatKind, PathSegment, QPath, Ty, TyKind};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, VariantDef};
use rustc_span::sym;
use super::{MATCH_WILDCARD_FOR_SINGLE_VARIANTS, WILDCARD_ENUM_MATCH_ARM};
#[allow(clippy::too_many_lines)]
pub(crate) fn check(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
let ty = cx.typeck_results().expr_ty(ex).peel_refs();
let adt_def = match ty.kind() {
ty::Adt(adt_def, _)
if adt_def.is_enum()
&& !(is_type_diagnostic_item(cx, ty, sym::Option) || is_type_diagnostic_item(cx, ty, sym::Result)) =>
{
adt_def
},
_ => return,
};
// First pass - check for violation, but don't do much book-keeping because this is hopefully
// the uncommon case, and the book-keeping is slightly expensive.
let mut wildcard_span = None;
let mut wildcard_ident = None;
let mut has_non_wild = false;
for arm in arms {
match peel_hir_pat_refs(arm.pat).0.kind {
PatKind::Wild => wildcard_span = Some(arm.pat.span),
PatKind::Binding(_, _, ident, None) => {
wildcard_span = Some(arm.pat.span);
wildcard_ident = Some(ident);
},
_ => has_non_wild = true,
}
}
let wildcard_span = match wildcard_span {
Some(x) if has_non_wild => x,
_ => return,
};
// Accumulate the variants which should be put in place of the wildcard because they're not
// already covered.
let has_hidden = adt_def.variants.iter().any(|x| is_hidden(cx, x));
let mut missing_variants: Vec<_> = adt_def.variants.iter().filter(|x| !is_hidden(cx, x)).collect();
let mut path_prefix = CommonPrefixSearcher::None;
for arm in arms {
// Guards mean that this case probably isn't exhaustively covered. Technically
// this is incorrect, as we should really check whether each variant is exhaustively
// covered by the set of guards that cover it, but that's really hard to do.
recurse_or_patterns(arm.pat, |pat| {
let path = match &peel_hir_pat_refs(pat).0.kind {
PatKind::Path(path) => {
#[allow(clippy::match_same_arms)]
let id = match cx.qpath_res(path, pat.hir_id) {
Res::Def(
DefKind::Const | DefKind::ConstParam | DefKind::AnonConst | DefKind::InlineConst,
_,
) => return,
Res::Def(_, id) => id,
_ => return,
};
if arm.guard.is_none() {
missing_variants.retain(|e| e.ctor_def_id != Some(id));
}
path
},
PatKind::TupleStruct(path, patterns, ..) => {
if let Some(id) = cx.qpath_res(path, pat.hir_id).opt_def_id() {
if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p)) {
missing_variants.retain(|e| e.ctor_def_id != Some(id));
}
}
path
},
PatKind::Struct(path, patterns, ..) => {
if let Some(id) = cx.qpath_res(path, pat.hir_id).opt_def_id() {
if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p.pat)) {
missing_variants.retain(|e| e.def_id != id);
}
}
path
},
_ => return,
};
match path {
QPath::Resolved(_, path) => path_prefix.with_path(path.segments),
QPath::TypeRelative(
Ty {
kind: TyKind::Path(QPath::Resolved(_, path)),
..
},
_,
) => path_prefix.with_prefix(path.segments),
_ => (),
}
});
}
let format_suggestion = |variant: &VariantDef| {
format!(
"{}{}{}{}",
if let Some(ident) = wildcard_ident {
format!("{} @ ", ident.name)
} else {
String::new()
},
if let CommonPrefixSearcher::Path(path_prefix) = path_prefix {
let mut s = String::new();
for seg in path_prefix {
s.push_str(seg.ident.as_str());
s.push_str("::");
}
s
} else {
let mut s = cx.tcx.def_path_str(adt_def.did);
s.push_str("::");
s
},
variant.name,
match variant.ctor_kind {
CtorKind::Fn if variant.fields.len() == 1 => "(_)",
CtorKind::Fn => "(..)",
CtorKind::Const => "",
CtorKind::Fictive => "{ .. }",
}
)
};
match missing_variants.as_slice() {
[] => (),
[x] if !adt_def.is_variant_list_non_exhaustive() && !has_hidden => span_lint_and_sugg(
cx,
MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
wildcard_span,
"wildcard matches only a single variant and will also match any future added variants",
"try this",
format_suggestion(x),
Applicability::MaybeIncorrect,
),
variants => {
let mut suggestions: Vec<_> = variants.iter().copied().map(format_suggestion).collect();
let message = if adt_def.is_variant_list_non_exhaustive() || has_hidden {
suggestions.push("_".into());
"wildcard matches known variants and will also match future added variants"
} else {
"wildcard match will also match any future added variants"
};
span_lint_and_sugg(
cx,
WILDCARD_ENUM_MATCH_ARM,
wildcard_span,
message,
"try this",
suggestions.join(" | "),
Applicability::MaybeIncorrect,
);
},
};
}
enum CommonPrefixSearcher<'a> {
None,
Path(&'a [PathSegment<'a>]),
Mixed,
}
impl<'a> CommonPrefixSearcher<'a> {
fn with_path(&mut self, path: &'a [PathSegment<'a>]) {
match path {
[path @ .., _] => self.with_prefix(path),
[] => (),
}
}
fn with_prefix(&mut self, path: &'a [PathSegment<'a>]) {
match self {
Self::None => *self = Self::Path(path),
Self::Path(self_path)
if path
.iter()
.map(|p| p.ident.name)
.eq(self_path.iter().map(|p| p.ident.name)) => {},
Self::Path(_) => *self = Self::Mixed,
Self::Mixed => (),
}
}
}
fn is_hidden(cx: &LateContext<'_>, variant_def: &VariantDef) -> bool {
let attrs = cx.tcx.get_attrs(variant_def.def_id);
clippy_utils::attrs::is_doc_hidden(attrs) || clippy_utils::attrs::is_unstable(attrs)
}

51
clippy_lints/src/matches/match_wild_err_arm.rs Normal file
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use clippy_utils::diagnostics::span_lint_and_note;
use clippy_utils::macros::{is_panic, root_macro_call};
use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::visitors::is_local_used;
use clippy_utils::{is_wild, peel_blocks_with_stmt};
use rustc_hir::{Arm, Expr, PatKind};
use rustc_lint::LateContext;
use rustc_span::symbol::{kw, sym};
use super::MATCH_WILD_ERR_ARM;
pub(crate) fn check<'tcx>(cx: &LateContext<'tcx>, ex: &Expr<'tcx>, arms: &[Arm<'tcx>]) {
let ex_ty = cx.typeck_results().expr_ty(ex).peel_refs();
if is_type_diagnostic_item(cx, ex_ty, sym::Result) {
for arm in arms {
if let PatKind::TupleStruct(ref path, inner, _) = arm.pat.kind {
let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
if path_str == "Err" {
let mut matching_wild = inner.iter().any(is_wild);
let mut ident_bind_name = kw::Underscore;
if !matching_wild {
// Looking for unused bindings (i.e.: `_e`)
for pat in inner.iter() {
if let PatKind::Binding(_, id, ident, None) = pat.kind {
if ident.as_str().starts_with('_') && !is_local_used(cx, arm.body, id) {
ident_bind_name = ident.name;
matching_wild = true;
}
}
}
}
if_chain! {
if matching_wild;
if let Some(macro_call) = root_macro_call(peel_blocks_with_stmt(arm.body).span);
if is_panic(cx, macro_call.def_id);
then {
// `Err(_)` or `Err(_e)` arm with `panic!` found
span_lint_and_note(cx,
MATCH_WILD_ERR_ARM,
arm.pat.span,
&format!("`Err({})` matches all errors", ident_bind_name),
None,
"match each error separately or use the error output, or use `.except(msg)` if the error case is unreachable",
);
}
}
}
}
}
}
}

646
clippy_lints/src/matches/mod.rs Normal file
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use clippy_utils::{meets_msrv, msrvs};
use rustc_hir::{Expr, ExprKind, Local, MatchSource, Pat};
use rustc_lint::{LateContext, LateLintPass};
use rustc_semver::RustcVersion;
use rustc_session::{declare_tool_lint, impl_lint_pass};
mod infalliable_detructuring_match;
mod match_as_ref;
mod match_bool;
mod match_like_matches;
mod match_ref_pats;
mod match_same_arms;
mod match_single_binding;
mod match_wild_enum;
mod match_wild_err_arm;
mod overlapping_arms;
mod redundant_pattern_match;
mod rest_pat_in_fully_bound_struct;
mod single_match;
mod wild_in_or_pats;
declare_clippy_lint! {
/// ### What it does
/// Checks for matches with a single arm where an `if let`
/// will usually suffice.
///
/// ### Why is this bad?
/// Just readability – `if let` nests less than a `match`.
///
/// ### Example
/// ```rust
/// # fn bar(stool: &str) {}
/// # let x = Some("abc");
/// // Bad
/// match x {
/// Some(ref foo) => bar(foo),
/// _ => (),
/// }
///
/// // Good
/// if let Some(ref foo) = x {
/// bar(foo);
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub SINGLE_MATCH,
style,
"a `match` statement with a single nontrivial arm (i.e., where the other arm is `_ => {}`) instead of `if let`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for matches with two arms where an `if let else` will
/// usually suffice.
///
/// ### Why is this bad?
/// Just readability – `if let` nests less than a `match`.
///
/// ### Known problems
/// Personal style preferences may differ.
///
/// ### Example
/// Using `match`:
///
/// ```rust
/// # fn bar(foo: &usize) {}
/// # let other_ref: usize = 1;
/// # let x: Option<&usize> = Some(&1);
/// match x {
/// Some(ref foo) => bar(foo),
/// _ => bar(&other_ref),
/// }
/// ```
///
/// Using `if let` with `else`:
///
/// ```rust
/// # fn bar(foo: &usize) {}
/// # let other_ref: usize = 1;
/// # let x: Option<&usize> = Some(&1);
/// if let Some(ref foo) = x {
/// bar(foo);
/// } else {
/// bar(&other_ref);
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub SINGLE_MATCH_ELSE,
pedantic,
"a `match` statement with two arms where the second arm's pattern is a placeholder instead of a specific match pattern"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for matches where all arms match a reference,
/// suggesting to remove the reference and deref the matched expression
/// instead. It also checks for `if let &foo = bar` blocks.
///
/// ### Why is this bad?
/// It just makes the code less readable. That reference
/// destructuring adds nothing to the code.
///
/// ### Example
/// ```rust,ignore
/// // Bad
/// match x {
/// &A(ref y) => foo(y),
/// &B => bar(),
/// _ => frob(&x),
/// }
///
/// // Good
/// match *x {
/// A(ref y) => foo(y),
/// B => bar(),
/// _ => frob(x),
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub MATCH_REF_PATS,
style,
"a `match` or `if let` with all arms prefixed with `&` instead of deref-ing the match expression"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for matches where match expression is a `bool`. It
/// suggests to replace the expression with an `if...else` block.
///
/// ### Why is this bad?
/// It makes the code less readable.
///
/// ### Example
/// ```rust
/// # fn foo() {}
/// # fn bar() {}
/// let condition: bool = true;
/// match condition {
/// true => foo(),
/// false => bar(),
/// }
/// ```
/// Use if/else instead:
/// ```rust
/// # fn foo() {}
/// # fn bar() {}
/// let condition: bool = true;
/// if condition {
/// foo();
/// } else {
/// bar();
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub MATCH_BOOL,
pedantic,
"a `match` on a boolean expression instead of an `if..else` block"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for overlapping match arms.
///
/// ### Why is this bad?
/// It is likely to be an error and if not, makes the code
/// less obvious.
///
/// ### Example
/// ```rust
/// let x = 5;
/// match x {
/// 1..=10 => println!("1 ... 10"),
/// 5..=15 => println!("5 ... 15"),
/// _ => (),
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub MATCH_OVERLAPPING_ARM,
style,
"a `match` with overlapping arms"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for arm which matches all errors with `Err(_)`
/// and take drastic actions like `panic!`.
///
/// ### Why is this bad?
/// It is generally a bad practice, similar to
/// catching all exceptions in java with `catch(Exception)`
///
/// ### Example
/// ```rust
/// let x: Result<i32, &str> = Ok(3);
/// match x {
/// Ok(_) => println!("ok"),
/// Err(_) => panic!("err"),
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub MATCH_WILD_ERR_ARM,
pedantic,
"a `match` with `Err(_)` arm and take drastic actions"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for match which is used to add a reference to an
/// `Option` value.
///
/// ### Why is this bad?
/// Using `as_ref()` or `as_mut()` instead is shorter.
///
/// ### Example
/// ```rust
/// let x: Option<()> = None;
///
/// // Bad
/// let r: Option<&()> = match x {
/// None => None,
/// Some(ref v) => Some(v),
/// };
///
/// // Good
/// let r: Option<&()> = x.as_ref();
/// ```
#[clippy::version = "pre 1.29.0"]
pub MATCH_AS_REF,
complexity,
"a `match` on an Option value instead of using `as_ref()` or `as_mut`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for wildcard enum matches using `_`.
///
/// ### Why is this bad?
/// New enum variants added by library updates can be missed.
///
/// ### Known problems
/// Suggested replacements may be incorrect if guards exhaustively cover some
/// variants, and also may not use correct path to enum if it's not present in the current scope.
///
/// ### Example
/// ```rust
/// # enum Foo { A(usize), B(usize) }
/// # let x = Foo::B(1);
/// // Bad
/// match x {
/// Foo::A(_) => {},
/// _ => {},
/// }
///
/// // Good
/// match x {
/// Foo::A(_) => {},
/// Foo::B(_) => {},
/// }
/// ```
#[clippy::version = "1.34.0"]
pub WILDCARD_ENUM_MATCH_ARM,
restriction,
"a wildcard enum match arm using `_`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for wildcard enum matches for a single variant.
///
/// ### Why is this bad?
/// New enum variants added by library updates can be missed.
///
/// ### Known problems
/// Suggested replacements may not use correct path to enum
/// if it's not present in the current scope.
///
/// ### Example
/// ```rust
/// # enum Foo { A, B, C }
/// # let x = Foo::B;
/// // Bad
/// match x {
/// Foo::A => {},
/// Foo::B => {},
/// _ => {},
/// }
///
/// // Good
/// match x {
/// Foo::A => {},
/// Foo::B => {},
/// Foo::C => {},
/// }
/// ```
#[clippy::version = "1.45.0"]
pub MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
pedantic,
"a wildcard enum match for a single variant"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for wildcard pattern used with others patterns in same match arm.
///
/// ### Why is this bad?
/// Wildcard pattern already covers any other pattern as it will match anyway.
/// It makes the code less readable, especially to spot wildcard pattern use in match arm.
///
/// ### Example
/// ```rust
/// // Bad
/// match "foo" {
/// "a" => {},
/// "bar" | _ => {},
/// }
///
/// // Good
/// match "foo" {
/// "a" => {},
/// _ => {},
/// }
/// ```
#[clippy::version = "1.42.0"]
pub WILDCARD_IN_OR_PATTERNS,
complexity,
"a wildcard pattern used with others patterns in same match arm"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for matches being used to destructure a single-variant enum
/// or tuple struct where a `let` will suffice.
///
/// ### Why is this bad?
/// Just readability – `let` doesn't nest, whereas a `match` does.
///
/// ### Example
/// ```rust
/// enum Wrapper {
/// Data(i32),
/// }
///
/// let wrapper = Wrapper::Data(42);
///
/// let data = match wrapper {
/// Wrapper::Data(i) => i,
/// };
/// ```
///
/// The correct use would be:
/// ```rust
/// enum Wrapper {
/// Data(i32),
/// }
///
/// let wrapper = Wrapper::Data(42);
/// let Wrapper::Data(data) = wrapper;
/// ```
#[clippy::version = "pre 1.29.0"]
pub INFALLIBLE_DESTRUCTURING_MATCH,
style,
"a `match` statement with a single infallible arm instead of a `let`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for useless match that binds to only one value.
///
/// ### Why is this bad?
/// Readability and needless complexity.
///
/// ### Known problems
/// Suggested replacements may be incorrect when `match`
/// is actually binding temporary value, bringing a 'dropped while borrowed' error.
///
/// ### Example
/// ```rust
/// # let a = 1;
/// # let b = 2;
///
/// // Bad
/// match (a, b) {
/// (c, d) => {
/// // useless match
/// }
/// }
///
/// // Good
/// let (c, d) = (a, b);
/// ```
#[clippy::version = "1.43.0"]
pub MATCH_SINGLE_BINDING,
complexity,
"a match with a single binding instead of using `let` statement"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for unnecessary '..' pattern binding on struct when all fields are explicitly matched.
///
/// ### Why is this bad?
/// Correctness and readability. It's like having a wildcard pattern after
/// matching all enum variants explicitly.
///
/// ### Example
/// ```rust
/// # struct A { a: i32 }
/// let a = A { a: 5 };
///
/// // Bad
/// match a {
/// A { a: 5, .. } => {},
/// _ => {},
/// }
///
/// // Good
/// match a {
/// A { a: 5 } => {},
/// _ => {},
/// }
/// ```
#[clippy::version = "1.43.0"]
pub REST_PAT_IN_FULLY_BOUND_STRUCTS,
restriction,
"a match on a struct that binds all fields but still uses the wildcard pattern"
}
declare_clippy_lint! {
/// ### What it does
/// Lint for redundant pattern matching over `Result`, `Option`,
/// `std::task::Poll` or `std::net::IpAddr`
///
/// ### Why is this bad?
/// It's more concise and clear to just use the proper
/// utility function
///
/// ### Known problems
/// This will change the drop order for the matched type. Both `if let` and
/// `while let` will drop the value at the end of the block, both `if` and `while` will drop the
/// value before entering the block. For most types this change will not matter, but for a few
/// types this will not be an acceptable change (e.g. locks). See the
/// [reference](https://doc.rust-lang.org/reference/destructors.html#drop-scopes) for more about
/// drop order.
///
/// ### Example
/// ```rust
/// # use std::task::Poll;
/// # use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
/// if let Ok(_) = Ok::<i32, i32>(42) {}
/// if let Err(_) = Err::<i32, i32>(42) {}
/// if let None = None::<()> {}
/// if let Some(_) = Some(42) {}
/// if let Poll::Pending = Poll::Pending::<()> {}
/// if let Poll::Ready(_) = Poll::Ready(42) {}
/// if let IpAddr::V4(_) = IpAddr::V4(Ipv4Addr::LOCALHOST) {}
/// if let IpAddr::V6(_) = IpAddr::V6(Ipv6Addr::LOCALHOST) {}
/// match Ok::<i32, i32>(42) {
/// Ok(_) => true,
/// Err(_) => false,
/// };
/// ```
///
/// The more idiomatic use would be:
///
/// ```rust
/// # use std::task::Poll;
/// # use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
/// if Ok::<i32, i32>(42).is_ok() {}
/// if Err::<i32, i32>(42).is_err() {}
/// if None::<()>.is_none() {}
/// if Some(42).is_some() {}
/// if Poll::Pending::<()>.is_pending() {}
/// if Poll::Ready(42).is_ready() {}
/// if IpAddr::V4(Ipv4Addr::LOCALHOST).is_ipv4() {}
/// if IpAddr::V6(Ipv6Addr::LOCALHOST).is_ipv6() {}
/// Ok::<i32, i32>(42).is_ok();
/// ```
#[clippy::version = "1.31.0"]
pub REDUNDANT_PATTERN_MATCHING,
style,
"use the proper utility function avoiding an `if let`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `match` or `if let` expressions producing a
/// `bool` that could be written using `matches!`
///
/// ### Why is this bad?
/// Readability and needless complexity.
///
/// ### Known problems
/// This lint falsely triggers, if there are arms with
/// `cfg` attributes that remove an arm evaluating to `false`.
///
/// ### Example
/// ```rust
/// let x = Some(5);
///
/// // Bad
/// let a = match x {
/// Some(0) => true,
/// _ => false,
/// };
///
/// let a = if let Some(0) = x {
/// true
/// } else {
/// false
/// };
///
/// // Good
/// let a = matches!(x, Some(0));
/// ```
#[clippy::version = "1.47.0"]
pub MATCH_LIKE_MATCHES_MACRO,
style,
"a match that could be written with the matches! macro"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `match` with identical arm bodies.
///
/// ### Why is this bad?
/// This is probably a copy & paste error. If arm bodies
/// are the same on purpose, you can factor them
/// [using `|`](https://doc.rust-lang.org/book/patterns.html#multiple-patterns).
///
/// ### Known problems
/// False positive possible with order dependent `match`
/// (see issue
/// [#860](https://github.com/rust-lang/rust-clippy/issues/860)).
///
/// ### Example
/// ```rust,ignore
/// match foo {
/// Bar => bar(),
/// Quz => quz(),
/// Baz => bar(), // <= oops
/// }
/// ```
///
/// This should probably be
/// ```rust,ignore
/// match foo {
/// Bar => bar(),
/// Quz => quz(),
/// Baz => baz(), // <= fixed
/// }
/// ```
///
/// or if the original code was not a typo:
/// ```rust,ignore
/// match foo {
/// Bar | Baz => bar(), // <= shows the intent better
/// Quz => quz(),
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub MATCH_SAME_ARMS,
pedantic,
"`match` with identical arm bodies"
}
#[derive(Default)]
pub struct Matches {
msrv: Option<RustcVersion>,
infallible_destructuring_match_linted: bool,
}
impl Matches {
#[must_use]
pub fn new(msrv: Option<RustcVersion>) -> Self {
Self {
msrv,
..Matches::default()
}
}
}
impl_lint_pass!(Matches => [
SINGLE_MATCH,
MATCH_REF_PATS,
MATCH_BOOL,
SINGLE_MATCH_ELSE,
MATCH_OVERLAPPING_ARM,
MATCH_WILD_ERR_ARM,
MATCH_AS_REF,
WILDCARD_ENUM_MATCH_ARM,
MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
WILDCARD_IN_OR_PATTERNS,
MATCH_SINGLE_BINDING,
INFALLIBLE_DESTRUCTURING_MATCH,
REST_PAT_IN_FULLY_BOUND_STRUCTS,
REDUNDANT_PATTERN_MATCHING,
MATCH_LIKE_MATCHES_MACRO,
MATCH_SAME_ARMS,
]);
impl<'tcx> LateLintPass<'tcx> for Matches {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if expr.span.from_expansion() {
return;
}
redundant_pattern_match::check(cx, expr);
if meets_msrv(self.msrv.as_ref(), &msrvs::MATCHES_MACRO) {
if !match_like_matches::check(cx, expr) {
match_same_arms::check(cx, expr);
}
} else {
match_same_arms::check(cx, expr);
}
if let ExprKind::Match(ex, arms, MatchSource::Normal) = expr.kind {
single_match::check(cx, ex, arms, expr);
match_bool::check(cx, ex, arms, expr);
overlapping_arms::check(cx, ex, arms);
match_wild_err_arm::check(cx, ex, arms);
match_wild_enum::check(cx, ex, arms);
match_as_ref::check(cx, ex, arms, expr);
wild_in_or_pats::check(cx, arms);
if self.infallible_destructuring_match_linted {
self.infallible_destructuring_match_linted = false;
} else {
match_single_binding::check(cx, ex, arms, expr);
}
}
if let ExprKind::Match(ex, arms, _) = expr.kind {
match_ref_pats::check(cx, ex, arms.iter().map(|el| el.pat), expr);
}
}
fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'_>) {
self.infallible_destructuring_match_linted |= infalliable_detructuring_match::check(cx, local);
}
fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) {
rest_pat_in_fully_bound_struct::check(cx, pat);
}
extract_msrv_attr!(LateContext);
}

181
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use clippy_utils::consts::{constant, constant_full_int, miri_to_const, FullInt};
use clippy_utils::diagnostics::span_lint_and_note;
use core::cmp::Ordering;
use rustc_hir::{Arm, Expr, PatKind, RangeEnd};
use rustc_lint::LateContext;
use rustc_middle::ty::Ty;
use rustc_span::Span;
use super::MATCH_OVERLAPPING_ARM;
pub(crate) fn check<'tcx>(cx: &LateContext<'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
if arms.len() >= 2 && cx.typeck_results().expr_ty(ex).is_integral() {
let ranges = all_ranges(cx, arms, cx.typeck_results().expr_ty(ex));
if !ranges.is_empty() {
if let Some((start, end)) = overlapping(&ranges) {
span_lint_and_note(
cx,
MATCH_OVERLAPPING_ARM,
start.span,
"some ranges overlap",
Some(end.span),
"overlaps with this",
);
}
}
}
}
/// Gets the ranges for each range pattern arm. Applies `ty` bounds for open ranges.
fn all_ranges<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>], ty: Ty<'tcx>) -> Vec<SpannedRange<FullInt>> {
arms.iter()
.filter_map(|arm| {
if let Arm { pat, guard: None, .. } = *arm {
if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
let lhs_const = match lhs {
Some(lhs) => constant(cx, cx.typeck_results(), lhs)?.0,
None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
};
let rhs_const = match rhs {
Some(rhs) => constant(cx, cx.typeck_results(), rhs)?.0,
None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
};
let lhs_val = lhs_const.int_value(cx, ty)?;
let rhs_val = rhs_const.int_value(cx, ty)?;
let rhs_bound = match range_end {
RangeEnd::Included => EndBound::Included(rhs_val),
RangeEnd::Excluded => EndBound::Excluded(rhs_val),
};
return Some(SpannedRange {
span: pat.span,
node: (lhs_val, rhs_bound),
});
}
if let PatKind::Lit(value) = pat.kind {
let value = constant_full_int(cx, cx.typeck_results(), value)?;
return Some(SpannedRange {
span: pat.span,
node: (value, EndBound::Included(value)),
});
}
}
None
})
.collect()
}
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum EndBound<T> {
Included(T),
Excluded(T),
}
#[derive(Debug, Eq, PartialEq)]
struct SpannedRange<T> {
pub span: Span,
pub node: (T, EndBound<T>),
}
fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
where
T: Copy + Ord,
{
#[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
enum BoundKind {
EndExcluded,
Start,
EndIncluded,
}
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
struct RangeBound<'a, T>(T, BoundKind, &'a SpannedRange<T>);
impl<'a, T: Copy + Ord> PartialOrd for RangeBound<'a, T> {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl<'a, T: Copy + Ord> Ord for RangeBound<'a, T> {
fn cmp(&self, RangeBound(other_value, other_kind, _): &Self) -> Ordering {
let RangeBound(self_value, self_kind, _) = *self;
(self_value, self_kind).cmp(&(*other_value, *other_kind))
}
}
let mut values = Vec::with_capacity(2 * ranges.len());
for r @ SpannedRange { node: (start, end), .. } in ranges {
values.push(RangeBound(*start, BoundKind::Start, r));
values.push(match end {
EndBound::Excluded(val) => RangeBound(*val, BoundKind::EndExcluded, r),
EndBound::Included(val) => RangeBound(*val, BoundKind::EndIncluded, r),
});
}
values.sort();
let mut started = vec![];
for RangeBound(_, kind, range) in values {
match kind {
BoundKind::Start => started.push(range),
BoundKind::EndExcluded | BoundKind::EndIncluded => {
let mut overlap = None;
while let Some(last_started) = started.pop() {
if last_started == range {
break;
}
overlap = Some(last_started);
}
if let Some(first_overlapping) = overlap {
return Some((range, first_overlapping));
}
},
}
}
None
}
#[test]
fn test_overlapping() {
use rustc_span::source_map::DUMMY_SP;
let sp = |s, e| SpannedRange {
span: DUMMY_SP,
node: (s, e),
};
assert_eq!(None, overlapping::<u8>(&[]));
assert_eq!(None, overlapping(&[sp(1, EndBound::Included(4))]));
assert_eq!(
None,
overlapping(&[sp(1, EndBound::Included(4)), sp(5, EndBound::Included(6))])
);
assert_eq!(
None,
overlapping(&[
sp(1, EndBound::Included(4)),
sp(5, EndBound::Included(6)),
sp(10, EndBound::Included(11))
],)
);
assert_eq!(
Some((&sp(1, EndBound::Included(4)), &sp(3, EndBound::Included(6)))),
overlapping(&[sp(1, EndBound::Included(4)), sp(3, EndBound::Included(6))])
);
assert_eq!(
Some((&sp(5, EndBound::Included(6)), &sp(6, EndBound::Included(11)))),
overlapping(&[
sp(1, EndBound::Included(4)),
sp(5, EndBound::Included(6)),
sp(6, EndBound::Included(11))
],)
);
}

436
clippy_lints/src/matches/redundant_pattern_match.rs Normal file
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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::{implements_trait, is_type_diagnostic_item, is_type_lang_item, match_type};
use clippy_utils::{higher, match_def_path};
use clippy_utils::{is_lang_ctor, is_trait_method, paths};
use if_chain::if_chain;
use rustc_ast::ast::LitKind;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::Applicability;
use rustc_hir::LangItem::{OptionNone, PollPending};
use rustc_hir::{
intravisit::{walk_expr, Visitor},
Arm, Block, Expr, ExprKind, LangItem, MatchSource, Node, Pat, PatKind, QPath, UnOp,
};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, subst::GenericArgKind, DefIdTree, Ty};
use rustc_span::sym;
pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if let Some(higher::IfLet {
if_else,
let_pat,
let_expr,
..
}) = higher::IfLet::hir(cx, expr)
{
find_sugg_for_if_let(cx, expr, let_pat, let_expr, "if", if_else.is_some());
}
if let ExprKind::Match(op, arms, MatchSource::Normal) = &expr.kind {
find_sugg_for_match(cx, expr, op, arms);
}
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);
}
}
/// Checks if the drop order for a type matters. Some std types implement drop solely to
/// deallocate memory. For these types, and composites containing them, changing the drop order
/// won't result in any observable side effects.
fn type_needs_ordered_drop<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
type_needs_ordered_drop_inner(cx, ty, &mut FxHashSet::default())
}
fn type_needs_ordered_drop_inner<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, seen: &mut FxHashSet<Ty<'tcx>>) -> bool {
if !seen.insert(ty) {
return false;
}
if !ty.needs_drop(cx.tcx, cx.param_env) {
false
} else if !cx
.tcx
.lang_items()
.drop_trait()
.map_or(false, |id| implements_trait(cx, ty, id, &[]))
{
// This type doesn't implement drop, so no side effects here.
// Check if any component type has any.
match ty.kind() {
ty::Tuple(_) => ty.tuple_fields().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
ty::Array(ty, _) => type_needs_ordered_drop_inner(cx, ty, seen),
ty::Adt(adt, subs) => adt
.all_fields()
.map(|f| f.ty(cx.tcx, subs))
.any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
_ => true,
}
}
// Check for std types which implement drop, but only for memory allocation.
else if is_type_diagnostic_item(cx, ty, sym::Vec)
|| is_type_lang_item(cx, ty, LangItem::OwnedBox)
|| is_type_diagnostic_item(cx, ty, sym::Rc)
|| is_type_diagnostic_item(cx, ty, sym::Arc)
|| is_type_diagnostic_item(cx, ty, sym::cstring_type)
|| is_type_diagnostic_item(cx, ty, sym::BTreeMap)
|| is_type_diagnostic_item(cx, ty, sym::LinkedList)
|| match_type(cx, ty, &paths::WEAK_RC)
|| match_type(cx, ty, &paths::WEAK_ARC)
{
// Check all of the generic arguments.
if let ty::Adt(_, subs) = ty.kind() {
subs.types().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen))
} else {
true
}
} else {
true
}
}
// 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
}
}
}
// Checks if there are any temporaries created in the given expression for which drop order
// matters.
fn temporaries_need_ordered_drop<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
struct V<'a, 'tcx> {
cx: &'a LateContext<'tcx>,
res: bool,
}
impl<'a, 'tcx> Visitor<'tcx> for V<'a, 'tcx> {
fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
match expr.kind {
// Taking the reference of a value leaves a temporary
// e.g. In `&String::new()` the string is a temporary value.
// Remaining fields are temporary values
// e.g. In `(String::new(), 0).1` the string is a temporary value.
ExprKind::AddrOf(_, _, expr) | ExprKind::Field(expr, _) => {
if !matches!(expr.kind, ExprKind::Path(_)) {
if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(expr)) {
self.res = true;
} else {
self.visit_expr(expr);
}
}
},
// the base type is alway taken by reference.
// e.g. In `(vec![0])[0]` the vector is a temporary value.
ExprKind::Index(base, index) => {
if !matches!(base.kind, ExprKind::Path(_)) {
if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(base)) {
self.res = true;
} else {
self.visit_expr(base);
}
}
self.visit_expr(index);
},
// Method calls can take self by reference.
// e.g. In `String::new().len()` the string is a temporary value.
ExprKind::MethodCall(_, [self_arg, args @ ..], _) => {
if !matches!(self_arg.kind, ExprKind::Path(_)) {
let self_by_ref = self
.cx
.typeck_results()
.type_dependent_def_id(expr.hir_id)
.map_or(false, |id| self.cx.tcx.fn_sig(id).skip_binder().inputs()[0].is_ref());
if self_by_ref && type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(self_arg)) {
self.res = true;
} else {
self.visit_expr(self_arg);
}
}
args.iter().for_each(|arg| self.visit_expr(arg));
},
// Either explicitly drops values, or changes control flow.
ExprKind::DropTemps(_)
| ExprKind::Ret(_)
| ExprKind::Break(..)
| ExprKind::Yield(..)
| ExprKind::Block(Block { expr: None, .. }, _)
| ExprKind::Loop(..) => (),
// Only consider the final expression.
ExprKind::Block(Block { expr: Some(expr), .. }, _) => self.visit_expr(expr),
_ => walk_expr(self, expr),
}
}
}
let mut v = V { cx, res: false };
v.visit_expr(expr);
v.res
}
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().and_then(|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 = type_needs_ordered_drop(cx, check_ty) || 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");
}
},
);
}
fn find_sugg_for_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
);
},
);
}
}
}
#[allow(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,
}
}

29
clippy_lints/src/matches/rest_pat_in_fully_bound_struct.rs Normal file
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use clippy_utils::diagnostics::span_lint_and_help;
use rustc_hir::{Pat, PatKind, QPath};
use rustc_lint::LateContext;
use rustc_middle::ty;
use super::REST_PAT_IN_FULLY_BOUND_STRUCTS;
pub(crate) fn check(cx: &LateContext<'_>, pat: &Pat<'_>) {
if_chain! {
if !pat.span.from_expansion();
if let PatKind::Struct(QPath::Resolved(_, path), fields, true) = pat.kind;
if let Some(def_id) = path.res.opt_def_id();
let ty = cx.tcx.type_of(def_id);
if let ty::Adt(def, _) = ty.kind();
if def.is_struct() || def.is_union();
if fields.len() == def.non_enum_variant().fields.len();
then {
span_lint_and_help(
cx,
REST_PAT_IN_FULLY_BOUND_STRUCTS,
pat.span,
"unnecessary use of `..` pattern in struct binding. All fields were already bound",
None,
"consider removing `..` from this binding",
);
}
}
}

269
clippy_lints/src/matches/single_match.rs Normal file
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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::{expr_block, snippet};
use clippy_utils::ty::{implements_trait, match_type, peel_mid_ty_refs};
use clippy_utils::{
is_lint_allowed, is_unit_expr, is_wild, paths, peel_blocks, peel_hir_pat_refs, peel_n_hir_expr_refs,
};
use core::cmp::max;
use rustc_errors::Applicability;
use rustc_hir::{Arm, BindingAnnotation, Block, Expr, ExprKind, Pat, PatKind};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty, TyS};
use super::{MATCH_BOOL, SINGLE_MATCH, SINGLE_MATCH_ELSE};
#[rustfmt::skip]
pub(crate) fn check(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
if expr.span.from_expansion() {
// Don't lint match expressions present in
// macro_rules! block
return;
}
if let PatKind::Or(..) = arms[0].pat.kind {
// don't lint for or patterns for now, this makes
// the lint noisy in unnecessary situations
return;
}
let els = arms[1].body;
let els = if is_unit_expr(peel_blocks(els)) {
None
} else if let ExprKind::Block(Block { stmts, expr: block_expr, .. }, _) = els.kind {
if stmts.len() == 1 && block_expr.is_none() || stmts.is_empty() && block_expr.is_some() {
// single statement/expr "else" block, don't lint
return;
}
// block with 2+ statements or 1 expr and 1+ statement
Some(els)
} else {
// not a block, don't lint
return;
};
let ty = cx.typeck_results().expr_ty(ex);
if *ty.kind() != ty::Bool || is_lint_allowed(cx, MATCH_BOOL, ex.hir_id) {
check_single_pattern(cx, ex, arms, expr, els);
check_opt_like(cx, ex, arms, expr, ty, els);
}
}
}
fn check_single_pattern(
cx: &LateContext<'_>,
ex: &Expr<'_>,
arms: &[Arm<'_>],
expr: &Expr<'_>,
els: Option<&Expr<'_>>,
) {
if is_wild(arms[1].pat) {
report_single_pattern(cx, ex, arms, expr, els);
}
}
fn report_single_pattern(
cx: &LateContext<'_>,
ex: &Expr<'_>,
arms: &[Arm<'_>],
expr: &Expr<'_>,
els: Option<&Expr<'_>>,
) {
let lint = if els.is_some() { SINGLE_MATCH_ELSE } else { SINGLE_MATCH };
let els_str = els.map_or(String::new(), |els| {
format!(" else {}", expr_block(cx, els, None, "..", Some(expr.span)))
});
let (pat, pat_ref_count) = peel_hir_pat_refs(arms[0].pat);
let (msg, sugg) = if_chain! {
if let PatKind::Path(_) | PatKind::Lit(_) = pat.kind;
let (ty, ty_ref_count) = peel_mid_ty_refs(cx.typeck_results().expr_ty(ex));
if let Some(spe_trait_id) = cx.tcx.lang_items().structural_peq_trait();
if let Some(pe_trait_id) = cx.tcx.lang_items().eq_trait();
if ty.is_integral() || ty.is_char() || ty.is_str()
|| (implements_trait(cx, ty, spe_trait_id, &[])
&& implements_trait(cx, ty, pe_trait_id, &[ty.into()]));
then {
// scrutinee derives PartialEq and the pattern is a constant.
let pat_ref_count = match pat.kind {
// string literals are already a reference.
PatKind::Lit(Expr { kind: ExprKind::Lit(lit), .. }) if lit.node.is_str() => pat_ref_count + 1,
_ => pat_ref_count,
};
// References are only implicitly added to the pattern, so no overflow here.
// e.g. will work: match &Some(_) { Some(_) => () }
// will not: match Some(_) { &Some(_) => () }
let ref_count_diff = ty_ref_count - pat_ref_count;
// Try to remove address of expressions first.
let (ex, removed) = peel_n_hir_expr_refs(ex, ref_count_diff);
let ref_count_diff = ref_count_diff - removed;
let msg = "you seem to be trying to use `match` for an equality check. Consider using `if`";
let sugg = format!(
"if {} == {}{} {}{}",
snippet(cx, ex.span, ".."),
// PartialEq for different reference counts may not exist.
"&".repeat(ref_count_diff),
snippet(cx, arms[0].pat.span, ".."),
expr_block(cx, arms[0].body, None, "..", Some(expr.span)),
els_str,
);
(msg, sugg)
} else {
let msg = "you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`";
let sugg = format!(
"if let {} = {} {}{}",
snippet(cx, arms[0].pat.span, ".."),
snippet(cx, ex.span, ".."),
expr_block(cx, arms[0].body, None, "..", Some(expr.span)),
els_str,
);
(msg, sugg)
}
};
span_lint_and_sugg(
cx,
lint,
expr.span,
msg,
"try this",
sugg,
Applicability::HasPlaceholders,
);
}
fn check_opt_like<'a>(
cx: &LateContext<'a>,
ex: &Expr<'_>,
arms: &[Arm<'_>],
expr: &Expr<'_>,
ty: Ty<'a>,
els: Option<&Expr<'_>>,
) {
// list of candidate `Enum`s we know will never get any more members
let candidates = &[
(&paths::COW, "Borrowed"),
(&paths::COW, "Cow::Borrowed"),
(&paths::COW, "Cow::Owned"),
(&paths::COW, "Owned"),
(&paths::OPTION, "None"),
(&paths::RESULT, "Err"),
(&paths::RESULT, "Ok"),
];
// We want to suggest to exclude an arm that contains only wildcards or forms the exhaustive
// match with the second branch, without enum variants in matches.
if !contains_only_wilds(arms[1].pat) && !form_exhaustive_matches(arms[0].pat, arms[1].pat) {
return;
}
let mut paths_and_types = Vec::new();
if !collect_pat_paths(&mut paths_and_types, cx, arms[1].pat, ty) {
return;
}
let in_candidate_enum = |path_info: &(String, &TyS<'_>)| -> bool {
let (path, ty) = path_info;
for &(ty_path, pat_path) in candidates {
if path == pat_path && match_type(cx, ty, ty_path) {
return true;
}
}
false
};
if paths_and_types.iter().all(in_candidate_enum) {
report_single_pattern(cx, ex, arms, expr, els);
}
}
/// Collects paths and their types from the given patterns. Returns true if the given pattern could
/// be simplified, false otherwise.
fn collect_pat_paths<'a>(acc: &mut Vec<(String, Ty<'a>)>, cx: &LateContext<'a>, pat: &Pat<'_>, ty: Ty<'a>) -> bool {
match pat.kind {
PatKind::Wild => true,
PatKind::Tuple(inner, _) => inner.iter().all(|p| {
let p_ty = cx.typeck_results().pat_ty(p);
collect_pat_paths(acc, cx, p, p_ty)
}),
PatKind::TupleStruct(ref path, ..) => {
let path = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| {
s.print_qpath(path, false);
});
acc.push((path, ty));
true
},
PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => {
acc.push((ident.to_string(), ty));
true
},
PatKind::Path(ref path) => {
let path = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| {
s.print_qpath(path, false);
});
acc.push((path, ty));
true
},
_ => false,
}
}
/// Returns true if the given arm of pattern matching contains wildcard patterns.
fn contains_only_wilds(pat: &Pat<'_>) -> bool {
match pat.kind {
PatKind::Wild => true,
PatKind::Tuple(inner, _) | PatKind::TupleStruct(_, inner, ..) => inner.iter().all(contains_only_wilds),
_ => false,
}
}
/// Returns true if the given patterns forms only exhaustive matches that don't contain enum
/// patterns without a wildcard.
fn form_exhaustive_matches(left: &Pat<'_>, right: &Pat<'_>) -> bool {
match (&left.kind, &right.kind) {
(PatKind::Wild, _) | (_, PatKind::Wild) => true,
(PatKind::Tuple(left_in, left_pos), PatKind::Tuple(right_in, right_pos)) => {
// We don't actually know the position and the presence of the `..` (dotdot) operator
// in the arms, so we need to evaluate the correct offsets here in order to iterate in
// both arms at the same time.
let len = max(
left_in.len() + {
if left_pos.is_some() { 1 } else { 0 }
},
right_in.len() + {
if right_pos.is_some() { 1 } else { 0 }
},
);
let mut left_pos = left_pos.unwrap_or(usize::MAX);
let mut right_pos = right_pos.unwrap_or(usize::MAX);
let mut left_dot_space = 0;
let mut right_dot_space = 0;
for i in 0..len {
let mut found_dotdot = false;
if i == left_pos {
left_dot_space += 1;
if left_dot_space < len - left_in.len() {
left_pos += 1;
}
found_dotdot = true;
}
if i == right_pos {
right_dot_space += 1;
if right_dot_space < len - right_in.len() {
right_pos += 1;
}
found_dotdot = true;
}
if found_dotdot {
continue;
}
if !contains_only_wilds(&left_in[i - left_dot_space])
&& !contains_only_wilds(&right_in[i - right_dot_space])
{
return false;
}
}
true
},
_ => false,
}
}

24
clippy_lints/src/matches/wild_in_or_pats.rs Normal file
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use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::is_wild;
use rustc_hir::{Arm, PatKind};
use rustc_lint::LateContext;
use super::WILDCARD_IN_OR_PATTERNS;
pub(crate) fn check(cx: &LateContext<'_>, arms: &[Arm<'_>]) {
for arm in arms {
if let PatKind::Or(fields) = arm.pat.kind {
// look for multiple fields in this arm that contains at least one Wild pattern
if fields.len() > 1 && fields.iter().any(is_wild) {
span_lint_and_help(
cx,
WILDCARD_IN_OR_PATTERNS,
arm.pat.span,
"wildcard pattern covers any other pattern as it will match anyway",
None,
"consider handling `_` separately",
);
}
}
}
}