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Move ManualMap into Matches lint pass

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This commit is contained in:
Jason Newcomb 2022-06-03 19:01:44 -04:00
parent 67cb5ec29f
commit 68c411ff94
7 changed files with 339 additions and 321 deletions
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2
clippy_lints/src/lib.register_all.rs
View file

@ -133,7 +133,6 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
LintId::of(main_recursion::MAIN_RECURSION), LintId::of(main_recursion::MAIN_RECURSION),
LintId::of(manual_async_fn::MANUAL_ASYNC_FN), LintId::of(manual_async_fn::MANUAL_ASYNC_FN),
LintId::of(manual_bits::MANUAL_BITS), LintId::of(manual_bits::MANUAL_BITS),
LintId::of(manual_map::MANUAL_MAP),
LintId::of(manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE), LintId::of(manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE),
LintId::of(manual_strip::MANUAL_STRIP), LintId::of(manual_strip::MANUAL_STRIP),
LintId::of(map_clone::MAP_CLONE), LintId::of(map_clone::MAP_CLONE),
@ -142,6 +141,7 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
LintId::of(match_result_ok::MATCH_RESULT_OK), LintId::of(match_result_ok::MATCH_RESULT_OK),
LintId::of(matches::COLLAPSIBLE_MATCH), LintId::of(matches::COLLAPSIBLE_MATCH),
LintId::of(matches::INFALLIBLE_DESTRUCTURING_MATCH), LintId::of(matches::INFALLIBLE_DESTRUCTURING_MATCH),
LintId::of(matches::MANUAL_MAP),
LintId::of(matches::MANUAL_UNWRAP_OR), LintId::of(matches::MANUAL_UNWRAP_OR),
LintId::of(matches::MATCH_AS_REF), LintId::of(matches::MATCH_AS_REF),
LintId::of(matches::MATCH_LIKE_MATCHES_MACRO), LintId::of(matches::MATCH_LIKE_MATCHES_MACRO),

2
clippy_lints/src/lib.register_lints.rs
View file

@ -250,7 +250,6 @@ store.register_lints(&[
manual_assert::MANUAL_ASSERT, manual_assert::MANUAL_ASSERT,
manual_async_fn::MANUAL_ASYNC_FN, manual_async_fn::MANUAL_ASYNC_FN,
manual_bits::MANUAL_BITS, manual_bits::MANUAL_BITS,
manual_map::MANUAL_MAP,
manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE, manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE,
manual_ok_or::MANUAL_OK_OR, manual_ok_or::MANUAL_OK_OR,
manual_strip::MANUAL_STRIP, manual_strip::MANUAL_STRIP,
@ -261,6 +260,7 @@ store.register_lints(&[
match_result_ok::MATCH_RESULT_OK, match_result_ok::MATCH_RESULT_OK,
matches::COLLAPSIBLE_MATCH, matches::COLLAPSIBLE_MATCH,
matches::INFALLIBLE_DESTRUCTURING_MATCH, matches::INFALLIBLE_DESTRUCTURING_MATCH,
matches::MANUAL_MAP,
matches::MANUAL_UNWRAP_OR, matches::MANUAL_UNWRAP_OR,
matches::MATCH_AS_REF, matches::MATCH_AS_REF,
matches::MATCH_BOOL, matches::MATCH_BOOL,

2
clippy_lints/src/lib.register_style.rs
View file

@ -45,12 +45,12 @@ store.register_group(true, "clippy::style", Some("clippy_style"), vec![
LintId::of(main_recursion::MAIN_RECURSION), LintId::of(main_recursion::MAIN_RECURSION),
LintId::of(manual_async_fn::MANUAL_ASYNC_FN), LintId::of(manual_async_fn::MANUAL_ASYNC_FN),
LintId::of(manual_bits::MANUAL_BITS), LintId::of(manual_bits::MANUAL_BITS),
LintId::of(manual_map::MANUAL_MAP),
LintId::of(manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE), LintId::of(manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE),
LintId::of(map_clone::MAP_CLONE), LintId::of(map_clone::MAP_CLONE),
LintId::of(match_result_ok::MATCH_RESULT_OK), LintId::of(match_result_ok::MATCH_RESULT_OK),
LintId::of(matches::COLLAPSIBLE_MATCH), LintId::of(matches::COLLAPSIBLE_MATCH),
LintId::of(matches::INFALLIBLE_DESTRUCTURING_MATCH), LintId::of(matches::INFALLIBLE_DESTRUCTURING_MATCH),
LintId::of(matches::MANUAL_MAP),
LintId::of(matches::MATCH_LIKE_MATCHES_MACRO), LintId::of(matches::MATCH_LIKE_MATCHES_MACRO),
LintId::of(matches::MATCH_OVERLAPPING_ARM), LintId::of(matches::MATCH_OVERLAPPING_ARM),
LintId::of(matches::MATCH_REF_PATS), LintId::of(matches::MATCH_REF_PATS),

2
clippy_lints/src/lib.rs
View file

@ -279,7 +279,6 @@ mod main_recursion;
mod manual_assert; mod manual_assert;
mod manual_async_fn; mod manual_async_fn;
mod manual_bits; mod manual_bits;
mod manual_map;
mod manual_non_exhaustive; mod manual_non_exhaustive;
mod manual_ok_or; mod manual_ok_or;
mod manual_strip; mod manual_strip;
@ -845,7 +844,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
}); });
store.register_late_pass(|| Box::new(redundant_slicing::RedundantSlicing)); store.register_late_pass(|| Box::new(redundant_slicing::RedundantSlicing));
store.register_late_pass(|| Box::new(from_str_radix_10::FromStrRadix10)); store.register_late_pass(|| Box::new(from_str_radix_10::FromStrRadix10));
store.register_late_pass(|| Box::new(manual_map::ManualMap));
store.register_late_pass(move || Box::new(if_then_some_else_none::IfThenSomeElseNone::new(msrv))); store.register_late_pass(move || Box::new(if_then_some_else_none::IfThenSomeElseNone::new(msrv)));
store.register_late_pass(|| Box::new(bool_assert_comparison::BoolAssertComparison)); store.register_late_pass(|| Box::new(bool_assert_comparison::BoolAssertComparison));
store.register_early_pass(move || Box::new(module_style::ModStyle)); store.register_early_pass(move || Box::new(module_style::ModStyle));

316
clippy_lints/src/manual_map.rs
View file

@ -1,316 +0,0 @@
use crate::{map_unit_fn::OPTION_MAP_UNIT_FN, matches::MATCH_AS_REF};
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::higher::IfLetOrMatch;
use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
use clippy_utils::ty::{is_type_diagnostic_item, peel_mid_ty_refs_is_mutable, type_is_unsafe_function};
use clippy_utils::{
can_move_expr_to_closure, in_constant, is_else_clause, is_lang_ctor, is_lint_allowed, path_to_local_id,
peel_blocks, peel_hir_expr_refs, peel_hir_expr_while, CaptureKind,
};
use rustc_ast::util::parser::PREC_POSTFIX;
use rustc_errors::Applicability;
use rustc_hir::LangItem::{OptionNone, OptionSome};
use rustc_hir::{
def::Res, Arm, BindingAnnotation, Block, BlockCheckMode, Expr, ExprKind, HirId, Mutability, Pat, PatKind, Path,
QPath, UnsafeSource,
};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::lint::in_external_macro;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::{sym, SyntaxContext};
declare_clippy_lint! {
/// ### What it does
/// Checks for usages of `match` which could be implemented using `map`
///
/// ### Why is this bad?
/// Using the `map` method is clearer and more concise.
///
/// ### Example
/// ```rust
/// match Some(0) {
/// Some(x) => Some(x + 1),
/// None => None,
/// };
/// ```
/// Use instead:
/// ```rust
/// Some(0).map(|x| x + 1);
/// ```
#[clippy::version = "1.52.0"]
pub MANUAL_MAP,
style,
"reimplementation of `map`"
}
declare_lint_pass!(ManualMap => [MANUAL_MAP]);
impl<'tcx> LateLintPass<'tcx> for ManualMap {
#[expect(clippy::too_many_lines)]
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
let (scrutinee, then_pat, then_body, else_pat, else_body) = match IfLetOrMatch::parse(cx, expr) {
Some(IfLetOrMatch::IfLet(scrutinee, pat, body, Some(r#else))) => (scrutinee, pat, body, None, r#else),
Some(IfLetOrMatch::Match(
scrutinee,
[arm1 @ Arm { guard: None, .. }, arm2 @ Arm { guard: None, .. }],
_,
)) => (scrutinee, arm1.pat, arm1.body, Some(arm2.pat), arm2.body),
_ => return,
};
if in_external_macro(cx.sess(), expr.span) || in_constant(cx, expr.hir_id) {
return;
}
let (scrutinee_ty, ty_ref_count, ty_mutability) =
peel_mid_ty_refs_is_mutable(cx.typeck_results().expr_ty(scrutinee));
if !(is_type_diagnostic_item(cx, scrutinee_ty, sym::Option)
&& is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::Option))
{
return;
}
let expr_ctxt = expr.span.ctxt();
let (some_expr, some_pat, pat_ref_count, is_wild_none) = match (
try_parse_pattern(cx, then_pat, expr_ctxt),
else_pat.map_or(Some(OptionPat::Wild), |p| try_parse_pattern(cx, p, expr_ctxt)),
) {
(Some(OptionPat::Wild), Some(OptionPat::Some { pattern, ref_count })) if is_none_expr(cx, then_body) => {
(else_body, pattern, ref_count, true)
},
(Some(OptionPat::None), Some(OptionPat::Some { pattern, ref_count })) if is_none_expr(cx, then_body) => {
(else_body, pattern, ref_count, false)
},
(Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::Wild)) if is_none_expr(cx, else_body) => {
(then_body, pattern, ref_count, true)
},
(Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::None)) if is_none_expr(cx, else_body) => {
(then_body, pattern, ref_count, false)
},
_ => return,
};
// Top level or patterns aren't allowed in closures.
if matches!(some_pat.kind, PatKind::Or(_)) {
return;
}
let some_expr = match get_some_expr(cx, some_expr, false, expr_ctxt) {
Some(expr) => expr,
None => return,
};
// These two lints will go back and forth with each other.
if cx.typeck_results().expr_ty(some_expr.expr) == cx.tcx.types.unit
&& !is_lint_allowed(cx, OPTION_MAP_UNIT_FN, expr.hir_id)
{
return;
}
// `map` won't perform any adjustments.
if !cx.typeck_results().expr_adjustments(some_expr.expr).is_empty() {
return;
}
// Determine which binding mode to use.
let explicit_ref = some_pat.contains_explicit_ref_binding();
let binding_ref = explicit_ref.or_else(|| (ty_ref_count != pat_ref_count).then(|| ty_mutability));
let as_ref_str = match binding_ref {
Some(Mutability::Mut) => ".as_mut()",
Some(Mutability::Not) => ".as_ref()",
None => "",
};
match can_move_expr_to_closure(cx, some_expr.expr) {
Some(captures) => {
// Check if captures the closure will need conflict with borrows made in the scrutinee.
// TODO: check all the references made in the scrutinee expression. This will require interacting
// with the borrow checker. Currently only `<local>[.<field>]*` is checked for.
if let Some(binding_ref_mutability) = binding_ref {
let e = peel_hir_expr_while(scrutinee, |e| match e.kind {
ExprKind::Field(e, _) | ExprKind::AddrOf(_, _, e) => Some(e),
_ => None,
});
if let ExprKind::Path(QPath::Resolved(None, Path { res: Res::Local(l), .. })) = e.kind {
match captures.get(l) {
Some(CaptureKind::Value | CaptureKind::Ref(Mutability::Mut)) => return,
Some(CaptureKind::Ref(Mutability::Not)) if binding_ref_mutability == Mutability::Mut => {
return;
},
Some(CaptureKind::Ref(Mutability::Not)) | None => (),
}
}
}
},
None => return,
};
let mut app = Applicability::MachineApplicable;
// Remove address-of expressions from the scrutinee. Either `as_ref` will be called, or
// it's being passed by value.
let scrutinee = peel_hir_expr_refs(scrutinee).0;
let (scrutinee_str, _) = snippet_with_context(cx, scrutinee.span, expr_ctxt, "..", &mut app);
let scrutinee_str =
if scrutinee.span.ctxt() == expr.span.ctxt() && scrutinee.precedence().order() < PREC_POSTFIX {
format!("({})", scrutinee_str)
} else {
scrutinee_str.into()
};
let body_str = if let PatKind::Binding(annotation, id, some_binding, None) = some_pat.kind {
if_chain! {
if !some_expr.needs_unsafe_block;
if let Some(func) = can_pass_as_func(cx, id, some_expr.expr);
if func.span.ctxt() == some_expr.expr.span.ctxt();
then {
snippet_with_applicability(cx, func.span, "..", &mut app).into_owned()
} else {
if path_to_local_id(some_expr.expr, id)
&& !is_lint_allowed(cx, MATCH_AS_REF, expr.hir_id)
&& binding_ref.is_some()
{
return;
}
// `ref` and `ref mut` annotations were handled earlier.
let annotation = if matches!(annotation, BindingAnnotation::Mutable) {
"mut "
} else {
""
};
let expr_snip = snippet_with_context(cx, some_expr.expr.span, expr_ctxt, "..", &mut app).0;
if some_expr.needs_unsafe_block {
format!("|{}{}| unsafe {{ {} }}", annotation, some_binding, expr_snip)
} else {
format!("|{}{}| {}", annotation, some_binding, expr_snip)
}
}
}
} else if !is_wild_none && explicit_ref.is_none() {
// TODO: handle explicit reference annotations.
let pat_snip = snippet_with_context(cx, some_pat.span, expr_ctxt, "..", &mut app).0;
let expr_snip = snippet_with_context(cx, some_expr.expr.span, expr_ctxt, "..", &mut app).0;
if some_expr.needs_unsafe_block {
format!("|{}| unsafe {{ {} }}", pat_snip, expr_snip)
} else {
format!("|{}| {}", pat_snip, expr_snip)
}
} else {
// Refutable bindings and mixed reference annotations can't be handled by `map`.
return;
};
span_lint_and_sugg(
cx,
MANUAL_MAP,
expr.span,
"manual implementation of `Option::map`",
"try this",
if else_pat.is_none() && is_else_clause(cx.tcx, expr) {
format!("{{ {}{}.map({}) }}", scrutinee_str, as_ref_str, body_str)
} else {
format!("{}{}.map({})", scrutinee_str, as_ref_str, body_str)
},
app,
);
}
}
// Checks whether the expression could be passed as a function, or whether a closure is needed.
// Returns the function to be passed to `map` if it exists.
fn can_pass_as_func<'tcx>(cx: &LateContext<'tcx>, binding: HirId, expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
match expr.kind {
ExprKind::Call(func, [arg])
if path_to_local_id(arg, binding)
&& cx.typeck_results().expr_adjustments(arg).is_empty()
&& !type_is_unsafe_function(cx, cx.typeck_results().expr_ty(func).peel_refs()) =>
{
Some(func)
},
_ => None,
}
}
enum OptionPat<'a> {
Wild,
None,
Some {
// The pattern contained in the `Some` tuple.
pattern: &'a Pat<'a>,
// The number of references before the `Some` tuple.
// e.g. `&&Some(_)` has a ref count of 2.
ref_count: usize,
},
}
struct SomeExpr<'tcx> {
expr: &'tcx Expr<'tcx>,
needs_unsafe_block: bool,
}
// Try to parse into a recognized `Option` pattern.
// i.e. `_`, `None`, `Some(..)`, or a reference to any of those.
fn try_parse_pattern<'tcx>(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
fn f<'tcx>(
cx: &LateContext<'tcx>,
pat: &'tcx Pat<'_>,
ref_count: usize,
ctxt: SyntaxContext,
) -> Option<OptionPat<'tcx>> {
match pat.kind {
PatKind::Wild => Some(OptionPat::Wild),
PatKind::Ref(pat, _) => f(cx, pat, ref_count + 1, ctxt),
PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone) => Some(OptionPat::None),
PatKind::TupleStruct(ref qpath, [pattern], _)
if is_lang_ctor(cx, qpath, OptionSome) && pat.span.ctxt() == ctxt =>
{
Some(OptionPat::Some { pattern, ref_count })
},
_ => None,
}
}
f(cx, pat, 0, ctxt)
}
// Checks for an expression wrapped by the `Some` constructor. Returns the contained expression.
fn get_some_expr<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'_>,
needs_unsafe_block: bool,
ctxt: SyntaxContext,
) -> Option<SomeExpr<'tcx>> {
// TODO: Allow more complex expressions.
match expr.kind {
ExprKind::Call(
Expr {
kind: ExprKind::Path(ref qpath),
..
},
[arg],
) if ctxt == expr.span.ctxt() && is_lang_ctor(cx, qpath, OptionSome) => Some(SomeExpr {
expr: arg,
needs_unsafe_block,
}),
ExprKind::Block(
Block {
stmts: [],
expr: Some(expr),
rules,
..
},
_,
) => get_some_expr(
cx,
expr,
needs_unsafe_block || *rules == BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided),
ctxt,
),
_ => None,
}
}
// Checks for the `None` value.
fn is_none_expr(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
matches!(peel_blocks(expr).kind, ExprKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone))
}

306
clippy_lints/src/matches/manual_map.rs Normal file
View file

@ -0,0 +1,306 @@
use crate::{map_unit_fn::OPTION_MAP_UNIT_FN, matches::MATCH_AS_REF};
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
use clippy_utils::ty::{is_type_diagnostic_item, peel_mid_ty_refs_is_mutable, type_is_unsafe_function};
use clippy_utils::{
can_move_expr_to_closure, is_else_clause, is_lang_ctor, is_lint_allowed, path_to_local_id, peel_blocks,
peel_hir_expr_refs, peel_hir_expr_while, CaptureKind,
};
use rustc_ast::util::parser::PREC_POSTFIX;
use rustc_errors::Applicability;
use rustc_hir::LangItem::{OptionNone, OptionSome};
use rustc_hir::{
def::Res, Arm, BindingAnnotation, Block, BlockCheckMode, Expr, ExprKind, HirId, Mutability, Pat, PatKind, Path,
QPath, UnsafeSource,
};
use rustc_lint::LateContext;
use rustc_span::{sym, SyntaxContext};
use super::MANUAL_MAP;
pub(super) fn check_match<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'_>,
scrutinee: &'tcx Expr<'_>,
arms: &'tcx [Arm<'_>],
) {
if let [arm1, arm2] = arms
&& arm1.guard.is_none()
&& arm2.guard.is_none()
{
check(cx, expr, scrutinee, arm1.pat, arm1.body, Some(arm2.pat), arm2.body);
}
}
pub(super) fn check_if_let<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'_>,
let_pat: &'tcx Pat<'_>,
let_expr: &'tcx Expr<'_>,
then_expr: &'tcx Expr<'_>,
else_expr: &'tcx Expr<'_>,
) {
check(cx, expr, let_expr, let_pat, then_expr, None, else_expr);
}
#[expect(clippy::too_many_lines)]
fn check<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'_>,
scrutinee: &'tcx Expr<'_>,
then_pat: &'tcx Pat<'_>,
then_body: &'tcx Expr<'_>,
else_pat: Option<&'tcx Pat<'_>>,
else_body: &'tcx Expr<'_>,
) {
let (scrutinee_ty, ty_ref_count, ty_mutability) =
peel_mid_ty_refs_is_mutable(cx.typeck_results().expr_ty(scrutinee));
if !(is_type_diagnostic_item(cx, scrutinee_ty, sym::Option)
&& is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::Option))
{
return;
}
let expr_ctxt = expr.span.ctxt();
let (some_expr, some_pat, pat_ref_count, is_wild_none) = match (
try_parse_pattern(cx, then_pat, expr_ctxt),
else_pat.map_or(Some(OptionPat::Wild), |p| try_parse_pattern(cx, p, expr_ctxt)),
) {
(Some(OptionPat::Wild), Some(OptionPat::Some { pattern, ref_count })) if is_none_expr(cx, then_body) => {
(else_body, pattern, ref_count, true)
},
(Some(OptionPat::None), Some(OptionPat::Some { pattern, ref_count })) if is_none_expr(cx, then_body) => {
(else_body, pattern, ref_count, false)
},
(Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::Wild)) if is_none_expr(cx, else_body) => {
(then_body, pattern, ref_count, true)
},
(Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::None)) if is_none_expr(cx, else_body) => {
(then_body, pattern, ref_count, false)
},
_ => return,
};
// Top level or patterns aren't allowed in closures.
if matches!(some_pat.kind, PatKind::Or(_)) {
return;
}
let some_expr = match get_some_expr(cx, some_expr, false, expr_ctxt) {
Some(expr) => expr,
None => return,
};
// These two lints will go back and forth with each other.
if cx.typeck_results().expr_ty(some_expr.expr) == cx.tcx.types.unit
&& !is_lint_allowed(cx, OPTION_MAP_UNIT_FN, expr.hir_id)
{
return;
}
// `map` won't perform any adjustments.
if !cx.typeck_results().expr_adjustments(some_expr.expr).is_empty() {
return;
}
// Determine which binding mode to use.
let explicit_ref = some_pat.contains_explicit_ref_binding();
let binding_ref = explicit_ref.or_else(|| (ty_ref_count != pat_ref_count).then(|| ty_mutability));
let as_ref_str = match binding_ref {
Some(Mutability::Mut) => ".as_mut()",
Some(Mutability::Not) => ".as_ref()",
None => "",
};
match can_move_expr_to_closure(cx, some_expr.expr) {
Some(captures) => {
// Check if captures the closure will need conflict with borrows made in the scrutinee.
// TODO: check all the references made in the scrutinee expression. This will require interacting
// with the borrow checker. Currently only `<local>[.<field>]*` is checked for.
if let Some(binding_ref_mutability) = binding_ref {
let e = peel_hir_expr_while(scrutinee, |e| match e.kind {
ExprKind::Field(e, _) | ExprKind::AddrOf(_, _, e) => Some(e),
_ => None,
});
if let ExprKind::Path(QPath::Resolved(None, Path { res: Res::Local(l), .. })) = e.kind {
match captures.get(l) {
Some(CaptureKind::Value | CaptureKind::Ref(Mutability::Mut)) => return,
Some(CaptureKind::Ref(Mutability::Not)) if binding_ref_mutability == Mutability::Mut => {
return;
},
Some(CaptureKind::Ref(Mutability::Not)) | None => (),
}
}
}
},
None => return,
};
let mut app = Applicability::MachineApplicable;
// Remove address-of expressions from the scrutinee. Either `as_ref` will be called, or
// it's being passed by value.
let scrutinee = peel_hir_expr_refs(scrutinee).0;
let (scrutinee_str, _) = snippet_with_context(cx, scrutinee.span, expr_ctxt, "..", &mut app);
let scrutinee_str = if scrutinee.span.ctxt() == expr.span.ctxt() && scrutinee.precedence().order() < PREC_POSTFIX {
format!("({})", scrutinee_str)
} else {
scrutinee_str.into()
};
let body_str = if let PatKind::Binding(annotation, id, some_binding, None) = some_pat.kind {
if_chain! {
if !some_expr.needs_unsafe_block;
if let Some(func) = can_pass_as_func(cx, id, some_expr.expr);
if func.span.ctxt() == some_expr.expr.span.ctxt();
then {
snippet_with_applicability(cx, func.span, "..", &mut app).into_owned()
} else {
if path_to_local_id(some_expr.expr, id)
&& !is_lint_allowed(cx, MATCH_AS_REF, expr.hir_id)
&& binding_ref.is_some()
{
return;
}
// `ref` and `ref mut` annotations were handled earlier.
let annotation = if matches!(annotation, BindingAnnotation::Mutable) {
"mut "
} else {
""
};
let expr_snip = snippet_with_context(cx, some_expr.expr.span, expr_ctxt, "..", &mut app).0;
if some_expr.needs_unsafe_block {
format!("|{}{}| unsafe {{ {} }}", annotation, some_binding, expr_snip)
} else {
format!("|{}{}| {}", annotation, some_binding, expr_snip)
}
}
}
} else if !is_wild_none && explicit_ref.is_none() {
// TODO: handle explicit reference annotations.
let pat_snip = snippet_with_context(cx, some_pat.span, expr_ctxt, "..", &mut app).0;
let expr_snip = snippet_with_context(cx, some_expr.expr.span, expr_ctxt, "..", &mut app).0;
if some_expr.needs_unsafe_block {
format!("|{}| unsafe {{ {} }}", pat_snip, expr_snip)
} else {
format!("|{}| {}", pat_snip, expr_snip)
}
} else {
// Refutable bindings and mixed reference annotations can't be handled by `map`.
return;
};
span_lint_and_sugg(
cx,
MANUAL_MAP,
expr.span,
"manual implementation of `Option::map`",
"try this",
if else_pat.is_none() && is_else_clause(cx.tcx, expr) {
format!("{{ {}{}.map({}) }}", scrutinee_str, as_ref_str, body_str)
} else {
format!("{}{}.map({})", scrutinee_str, as_ref_str, body_str)
},
app,
);
}
// Checks whether the expression could be passed as a function, or whether a closure is needed.
// Returns the function to be passed to `map` if it exists.
fn can_pass_as_func<'tcx>(cx: &LateContext<'tcx>, binding: HirId, expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
match expr.kind {
ExprKind::Call(func, [arg])
if path_to_local_id(arg, binding)
&& cx.typeck_results().expr_adjustments(arg).is_empty()
&& !type_is_unsafe_function(cx, cx.typeck_results().expr_ty(func).peel_refs()) =>
{
Some(func)
},
_ => None,
}
}
enum OptionPat<'a> {
Wild,
None,
Some {
// The pattern contained in the `Some` tuple.
pattern: &'a Pat<'a>,
// The number of references before the `Some` tuple.
// e.g. `&&Some(_)` has a ref count of 2.
ref_count: usize,
},
}
struct SomeExpr<'tcx> {
expr: &'tcx Expr<'tcx>,
needs_unsafe_block: bool,
}
// Try to parse into a recognized `Option` pattern.
// i.e. `_`, `None`, `Some(..)`, or a reference to any of those.
fn try_parse_pattern<'tcx>(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
fn f<'tcx>(
cx: &LateContext<'tcx>,
pat: &'tcx Pat<'_>,
ref_count: usize,
ctxt: SyntaxContext,
) -> Option<OptionPat<'tcx>> {
match pat.kind {
PatKind::Wild => Some(OptionPat::Wild),
PatKind::Ref(pat, _) => f(cx, pat, ref_count + 1, ctxt),
PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone) => Some(OptionPat::None),
PatKind::TupleStruct(ref qpath, [pattern], _)
if is_lang_ctor(cx, qpath, OptionSome) && pat.span.ctxt() == ctxt =>
{
Some(OptionPat::Some { pattern, ref_count })
},
_ => None,
}
}
f(cx, pat, 0, ctxt)
}
// Checks for an expression wrapped by the `Some` constructor. Returns the contained expression.
fn get_some_expr<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'_>,
needs_unsafe_block: bool,
ctxt: SyntaxContext,
) -> Option<SomeExpr<'tcx>> {
// TODO: Allow more complex expressions.
match expr.kind {
ExprKind::Call(
Expr {
kind: ExprKind::Path(ref qpath),
..
},
[arg],
) if ctxt == expr.span.ctxt() && is_lang_ctor(cx, qpath, OptionSome) => Some(SomeExpr {
expr: arg,
needs_unsafe_block,
}),
ExprKind::Block(
Block {
stmts: [],
expr: Some(expr),
rules,
..
},
_,
) => get_some_expr(
cx,
expr,
needs_unsafe_block || *rules == BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided),
ctxt,
),
_ => None,
}
}
// Checks for the `None` value.
fn is_none_expr(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
matches!(peel_blocks(expr).kind, ExprKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone))
}

30
clippy_lints/src/matches/mod.rs
View file

@ -10,6 +10,7 @@ use rustc_span::{Span, SpanData, SyntaxContext};
mod collapsible_match; mod collapsible_match;
mod infallible_destructuring_match; mod infallible_destructuring_match;
mod manual_map;
mod manual_unwrap_or; mod manual_unwrap_or;
mod match_as_ref; mod match_as_ref;
mod match_bool; mod match_bool;
@ -861,6 +862,30 @@ declare_clippy_lint! {
"return errors explicitly rather than hiding them behind a `?`" "return errors explicitly rather than hiding them behind a `?`"
} }
declare_clippy_lint! {
/// ### What it does
/// Checks for usages of `match` which could be implemented using `map`
///
/// ### Why is this bad?
/// Using the `map` method is clearer and more concise.
///
/// ### Example
/// ```rust
/// match Some(0) {
/// Some(x) => Some(x + 1),
/// None => None,
/// };
/// ```
/// Use instead:
/// ```rust
/// Some(0).map(|x| x + 1);
/// ```
#[clippy::version = "1.52.0"]
pub MANUAL_MAP,
style,
"reimplementation of `map`"
}
#[derive(Default)] #[derive(Default)]
pub struct Matches { pub struct Matches {
msrv: Option<RustcVersion>, msrv: Option<RustcVersion>,
@ -901,6 +926,7 @@ impl_lint_pass!(Matches => [
MATCH_STR_CASE_MISMATCH, MATCH_STR_CASE_MISMATCH,
SIGNIFICANT_DROP_IN_SCRUTINEE, SIGNIFICANT_DROP_IN_SCRUTINEE,
TRY_ERR, TRY_ERR,
MANUAL_MAP,
]); ]);
impl<'tcx> LateLintPass<'tcx> for Matches { impl<'tcx> LateLintPass<'tcx> for Matches {
@ -949,6 +975,7 @@ impl<'tcx> LateLintPass<'tcx> for Matches {
if !in_constant(cx, expr.hir_id) { if !in_constant(cx, expr.hir_id) {
manual_unwrap_or::check(cx, expr, ex, arms); manual_unwrap_or::check(cx, expr, ex, arms);
manual_map::check_match(cx, expr, ex, arms);
} }
if self.infallible_destructuring_match_linted { if self.infallible_destructuring_match_linted {
@ -973,6 +1000,9 @@ impl<'tcx> LateLintPass<'tcx> for Matches {
else_expr, else_expr,
); );
} }
if !in_constant(cx, expr.hir_id) {
manual_map::check_if_let(cx, expr, if_let.let_pat, if_let.let_expr, if_let.if_then, else_expr);
}
} }
redundant_pattern_match::check_if_let( redundant_pattern_match::check_if_let(
cx, cx,