Skip to content

Commit

Permalink
Auto merge of #8549 - J-ZhengLi:issue8542, r=llogiq
Browse files Browse the repository at this point in the history 
fix FP in lint `[needless_match]`

fixes: #8542
fixes: #8551
fixes: #8595
fixes: #8599

---

changelog: check for more complex custom type, and ignore type coercion in [`needless_match`]
  • Loading branch information
@bors
bors committed Apr 6, 2022
2 parents 30019d1 + 85b081b commit 81e004a
Show file tree
Hide file tree
Showing 5 changed files with 425 additions and 196 deletions.
2 changes: 1 addition & 1 deletion clippy_lints/src/matches/mod.rs
View file
Expand Up @@ -667,7 +667,7 @@ impl<'tcx> LateLintPass<'tcx> for Matches {
overlapping_arms::check(cx, ex, arms);
match_wild_enum::check(cx, ex, arms);
match_as_ref::check(cx, ex, arms, expr);
needless_match::check_match(cx, ex, arms);
needless_match::check_match(cx, ex, arms, expr);

if self.infallible_destructuring_match_linted {
self.infallible_destructuring_match_linted = false;
Expand Down
160 changes: 86 additions & 74 deletions clippy_lints/src/matches/needless_match.rs
View file
@@ -1,37 +1,25 @@
use super::NEEDLESS_MATCH;
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::{eq_expr_value, get_parent_expr, higher, is_else_clause, is_lang_ctor, peel_blocks_with_stmt};
use clippy_utils::ty::{is_type_diagnostic_item, same_type_and_consts};
use clippy_utils::{
eq_expr_value, get_parent_expr_for_hir, get_parent_node, higher, is_else_clause, is_lang_ctor, over,
peel_blocks_with_stmt,
};
use rustc_errors::Applicability;
use rustc_hir::LangItem::OptionNone;
use rustc_hir::{Arm, BindingAnnotation, Expr, ExprKind, Pat, PatKind, Path, PathSegment, QPath, UnOp};
use rustc_hir::{Arm, BindingAnnotation, Expr, ExprKind, FnRetTy, Node, Pat, PatKind, Path, QPath};
use rustc_lint::LateContext;
use rustc_span::sym;
use rustc_typeck::hir_ty_to_ty;

pub(crate) fn check_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
// This is for avoiding collision with `match_single_binding`.
if arms.len() < 2 {
return;
}

for arm in arms {
if let PatKind::Wild = arm.pat.kind {
let ret_expr = strip_return(arm.body);
if !eq_expr_value(cx, ex, ret_expr) {
return;
}
} else if !pat_same_as_expr(arm.pat, arm.body) {
return;
}
}

if let Some(match_expr) = get_parent_expr(cx, ex) {
pub(crate) fn check_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
if arms.len() > 1 && expr_ty_matches_p_ty(cx, ex, expr) && check_all_arms(cx, ex, arms) {
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
NEEDLESS_MATCH,
match_expr.span,
expr.span,
"this match expression is unnecessary",
"replace it with",
snippet_with_applicability(cx, ex.span, "..", &mut applicability).to_string(),
Expand Down Expand Up @@ -60,11 +48,8 @@ pub(crate) fn check_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>])
/// }
/// ```
pub(crate) fn check(cx: &LateContext<'_>, ex: &Expr<'_>) {
if_chain! {
if let Some(ref if_let) = higher::IfLet::hir(cx, ex);
if !is_else_clause(cx.tcx, ex);
if check_if_let(cx, if_let);
then {
if let Some(ref if_let) = higher::IfLet::hir(cx, ex) {
if !is_else_clause(cx.tcx, ex) && expr_ty_matches_p_ty(cx, if_let.let_expr, ex) && check_if_let(cx, if_let) {
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
Expand All @@ -79,6 +64,19 @@ pub(crate) fn check(cx: &LateContext<'_>, ex: &Expr<'_>) {
}
}

fn check_all_arms(cx: &LateContext<'_>, match_expr: &Expr<'_>, arms: &[Arm<'_>]) -> bool {
for arm in arms {
let arm_expr = peel_blocks_with_stmt(arm.body);
if let PatKind::Wild = arm.pat.kind {
return eq_expr_value(cx, match_expr, strip_return(arm_expr));
} else if !pat_same_as_expr(arm.pat, arm_expr) {
return false;
}
}

true
}

fn check_if_let(cx: &LateContext<'_>, if_let: &higher::IfLet<'_>) -> bool {
if let Some(if_else) = if_let.if_else {
if !pat_same_as_expr(if_let.let_pat, peel_blocks_with_stmt(if_let.if_then)) {
Expand All @@ -92,18 +90,21 @@ fn check_if_let(cx: &LateContext<'_>, if_let: &higher::IfLet<'_>) -> bool {

if matches!(if_else.kind, ExprKind::Block(..)) {
let else_expr = peel_blocks_with_stmt(if_else);
if matches!(else_expr.kind, ExprKind::Block(..)) {
return false;
}
let ret = strip_return(else_expr);
let let_expr_ty = cx.typeck_results().expr_ty(if_let.let_expr);
if is_type_diagnostic_item(cx, let_expr_ty, sym::Option) {
if let ExprKind::Path(ref qpath) = ret.kind {
return is_lang_ctor(cx, qpath, OptionNone) || eq_expr_value(cx, if_let.let_expr, ret);
}
} else {
return eq_expr_value(cx, if_let.let_expr, ret);
return true;
}
return true;
return eq_expr_value(cx, if_let.let_expr, ret);
}
}

false
}

Expand All @@ -116,48 +117,70 @@ fn strip_return<'hir>(expr: &'hir Expr<'hir>) -> &'hir Expr<'hir> {
}
}

/// Manually check for coercion casting by checking if the type of the match operand or let expr
/// differs with the assigned local variable or the funtion return type.
fn expr_ty_matches_p_ty(cx: &LateContext<'_>, expr: &Expr<'_>, p_expr: &Expr<'_>) -> bool {
if let Some(p_node) = get_parent_node(cx.tcx, p_expr.hir_id) {
match p_node {
// Compare match_expr ty with local in `let local = match match_expr {..}`
Node::Local(local) => {
let results = cx.typeck_results();
return same_type_and_consts(results.node_type(local.hir_id), results.expr_ty(expr));
},
// compare match_expr ty with RetTy in `fn foo() -> RetTy`
Node::Item(..) => {
if let Some(fn_decl) = p_node.fn_decl() {
if let FnRetTy::Return(ret_ty) = fn_decl.output {
return same_type_and_consts(hir_ty_to_ty(cx.tcx, ret_ty), cx.typeck_results().expr_ty(expr));
}
}
},
// check the parent expr for this whole block `{ match match_expr {..} }`
Node::Block(block) => {
if let Some(block_parent_expr) = get_parent_expr_for_hir(cx, block.hir_id) {
return expr_ty_matches_p_ty(cx, expr, block_parent_expr);
}
},
// recursively call on `if xxx {..}` etc.
Node::Expr(p_expr) => {
return expr_ty_matches_p_ty(cx, expr, p_expr);
},
_ => {},
}
}
false
}

fn pat_same_as_expr(pat: &Pat<'_>, expr: &Expr<'_>) -> bool {
let expr = strip_return(expr);
match (&pat.kind, &expr.kind) {
// Example: `Some(val) => Some(val)`
(
PatKind::TupleStruct(QPath::Resolved(_, path), [first_pat, ..], _),
ExprKind::Call(call_expr, [first_param, ..]),
) => {
(PatKind::TupleStruct(QPath::Resolved(_, path), tuple_params, _), ExprKind::Call(call_expr, call_params)) => {
if let ExprKind::Path(QPath::Resolved(_, call_path)) = call_expr.kind {
if has_identical_segments(path.segments, call_path.segments)
&& has_same_non_ref_symbol(first_pat, first_param)
{
return true;
}
return over(path.segments, call_path.segments, |pat_seg, call_seg| {
pat_seg.ident.name == call_seg.ident.name
}) && same_non_ref_symbols(tuple_params, call_params);
}
},
// Example: `val => val`, or `ref val => *val`
(PatKind::Binding(annot, _, pat_ident, _), _) => {
let new_expr = if let (
BindingAnnotation::Ref | BindingAnnotation::RefMut,
ExprKind::Unary(UnOp::Deref, operand_expr),
) = (annot, &expr.kind)
{
operand_expr
} else {
expr
};

if let ExprKind::Path(QPath::Resolved(
// Example: `val => val`
(
PatKind::Binding(annot, _, pat_ident, _),
ExprKind::Path(QPath::Resolved(
_,
Path {
segments: [first_seg, ..],
..
},
)) = new_expr.kind
{
return pat_ident.name == first_seg.ident.name;
}
)),
) => {
return !matches!(annot, BindingAnnotation::Ref | BindingAnnotation::RefMut)
&& pat_ident.name == first_seg.ident.name;
},
// Example: `Custom::TypeA => Custom::TypeB`, or `None => None`
(PatKind::Path(QPath::Resolved(_, p_path)), ExprKind::Path(QPath::Resolved(_, e_path))) => {
return has_identical_segments(p_path.segments, e_path.segments);
return over(p_path.segments, e_path.segments, |p_seg, e_seg| {
p_seg.ident.name == e_seg.ident.name
});
},
// Example: `5 => 5`
(PatKind::Lit(pat_lit_expr), ExprKind::Lit(expr_spanned)) => {
Expand All @@ -171,27 +194,16 @@ fn pat_same_as_expr(pat: &Pat<'_>, expr: &Expr<'_>) -> bool {
false
}

fn has_identical_segments(left_segs: &[PathSegment<'_>], right_segs: &[PathSegment<'_>]) -> bool {
if left_segs.len() != right_segs.len() {
fn same_non_ref_symbols(pats: &[Pat<'_>], exprs: &[Expr<'_>]) -> bool {
if pats.len() != exprs.len() {
return false;
}
for i in 0..left_segs.len() {
if left_segs[i].ident.name != right_segs[i].ident.name {
return false;
}
}
true
}

fn has_same_non_ref_symbol(pat: &Pat<'_>, expr: &Expr<'_>) -> bool {
if_chain! {
if let PatKind::Binding(annot, _, pat_ident, _) = pat.kind;
if !matches!(annot, BindingAnnotation::Ref | BindingAnnotation::RefMut);
if let ExprKind::Path(QPath::Resolved(_, Path {segments: [first_seg, ..], .. })) = expr.kind;
then {
return pat_ident.name == first_seg.ident.name;
for i in 0..pats.len() {
if !pat_same_as_expr(&pats[i], &exprs[i]) {
return false;
}
}

false
true
}

0 comments on commit 81e004a

Please sign in to comment.