rust-clippy/clippy_lints/src/matches.rs
xFrednet a37af06fea Removing false positive for the match_single_binding lint
* Applying suggested changes from the PR
2020-12-13 20:49:39 +00:00

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use crate::consts::{constant, miri_to_const, Constant};
use crate::utils::sugg::Sugg;
use crate::utils::usage::is_unused;
use crate::utils::{
expr_block, get_arg_name, get_parent_expr, in_macro, indent_of, is_allowed, is_expn_of, is_refutable,
is_type_diagnostic_item, is_wild, match_qpath, match_type, match_var, meets_msrv, multispan_sugg, remove_blocks,
snippet, snippet_block, snippet_opt, snippet_with_applicability, span_lint_and_help, span_lint_and_note,
span_lint_and_sugg, span_lint_and_then,
};
use crate::utils::{paths, search_same, SpanlessEq, SpanlessHash};
use if_chain::if_chain;
use rustc_ast::ast::LitKind;
use rustc_data_structures::fx::FxHashMap;
use rustc_errors::Applicability;
use rustc_hir::def::CtorKind;
use rustc_hir::{
Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Guard, Local, MatchSource, Mutability, Node, Pat,
PatKind, QPath, RangeEnd,
};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::lint::in_external_macro;
use rustc_middle::ty::{self, Ty, TyS};
use rustc_semver::RustcVersion;
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::source_map::{Span, Spanned};
use rustc_span::{sym, Symbol};
use std::cmp::Ordering;
use std::collections::hash_map::Entry;
use std::collections::Bound;
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`.
///
/// **Known problems:** None.
///
/// **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);
/// }
/// ```
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);
/// }
/// ```
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.
///
/// **Known problems:** None.
///
/// **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),
/// }
/// ```
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.
///
/// **Known problems:** None.
///
/// **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();
/// }
/// ```
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.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// let x = 5;
/// match x {
/// 1...10 => println!("1 ... 10"),
/// 5...15 => println!("5 ... 15"),
/// _ => (),
/// }
/// ```
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)`
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// let x: Result<i32, &str> = Ok(3);
/// match x {
/// Ok(_) => println!("ok"),
/// Err(_) => panic!("err"),
/// }
/// ```
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.
///
/// **Known problems:** None.
///
/// **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();
/// ```
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(_) => {},
/// }
/// ```
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 => {},
/// }
/// ```
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.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// // Bad
/// match "foo" {
/// "a" => {},
/// "bar" | _ => {},
/// }
///
/// // Good
/// match "foo" {
/// "a" => {},
/// _ => {},
/// }
/// ```
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.
///
/// **Known problems:** None.
///
/// **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;
/// ```
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);
/// ```
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.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// # struct A { a: i32 }
/// let a = A { a: 5 };
///
/// // Bad
/// match a {
/// A { a: 5, .. } => {},
/// _ => {},
/// }
///
/// // Good
/// match a {
/// A { a: 5 } => {},
/// _ => {},
/// }
/// ```
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:** None.
///
/// **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();
/// ```
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));
/// ```
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(),
/// }
/// ```
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,
]);
const MATCH_LIKE_MATCHES_MACRO_MSRV: RustcVersion = RustcVersion::new(1, 42, 0);
impl<'tcx> LateLintPass<'tcx> for Matches {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if in_external_macro(cx.sess(), expr.span) || in_macro(expr.span) {
return;
}
redundant_pattern_match::check(cx, expr);
if meets_msrv(self.msrv.as_ref(), &MATCH_LIKE_MATCHES_MACRO_MSRV) {
if !check_match_like_matches(cx, expr) {
lint_match_arms(cx, expr);
}
} else {
lint_match_arms(cx, expr);
}
if let ExprKind::Match(ref ex, ref arms, MatchSource::Normal) = expr.kind {
check_single_match(cx, ex, arms, expr);
check_match_bool(cx, ex, arms, expr);
check_overlapping_arms(cx, ex, arms);
check_wild_err_arm(cx, ex, arms);
check_wild_enum_match(cx, ex, arms);
check_match_as_ref(cx, ex, arms, expr);
check_wild_in_or_pats(cx, arms);
if self.infallible_destructuring_match_linted {
self.infallible_destructuring_match_linted = false;
} else {
check_match_single_binding(cx, ex, arms, expr);
}
}
if let ExprKind::Match(ref ex, ref arms, _) = expr.kind {
check_match_ref_pats(cx, ex, arms, expr);
}
}
fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'_>) {
if_chain! {
if !in_external_macro(cx.sess(), local.span);
if !in_macro(local.span);
if let Some(ref expr) = local.init;
if let ExprKind::Match(ref target, ref arms, MatchSource::Normal) = expr.kind;
if arms.len() == 1 && arms[0].guard.is_none();
if let PatKind::TupleStruct(
QPath::Resolved(None, ref variant_name), ref args, _) = arms[0].pat.kind;
if args.len() == 1;
if let Some(arg) = get_arg_name(&args[0]);
let body = remove_blocks(&arms[0].body);
if match_var(body, arg);
then {
let mut applicability = Applicability::MachineApplicable;
self.infallible_destructuring_match_linted = true;
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,
);
}
}
}
fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) {
if_chain! {
if !in_external_macro(cx.sess(), pat.span);
if !in_macro(pat.span);
if let PatKind::Struct(QPath::Resolved(_, ref 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",
);
}
}
}
extract_msrv_attr!(LateContext);
}
#[rustfmt::skip]
fn check_single_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
if in_macro(expr.span) {
// 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(remove_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_allowed(cx, MATCH_BOOL, ex.hir_id) {
check_single_match_single_pattern(cx, ex, arms, expr, els);
check_single_match_opt_like(cx, ex, arms, expr, ty, els);
}
}
}
fn check_single_match_single_pattern(
cx: &LateContext<'_>,
ex: &Expr<'_>,
arms: &[Arm<'_>],
expr: &Expr<'_>,
els: Option<&Expr<'_>>,
) {
if is_wild(&arms[1].pat) {
report_single_match_single_pattern(cx, ex, arms, expr, els);
}
}
fn report_single_match_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)))
});
span_lint_and_sugg(
cx,
lint,
expr.span,
"you seem to be trying to use match for destructuring a single pattern. Consider using `if \
let`",
"try this",
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,
),
Applicability::HasPlaceholders,
);
}
fn check_single_match_opt_like(
cx: &LateContext<'_>,
ex: &Expr<'_>,
arms: &[Arm<'_>],
expr: &Expr<'_>,
ty: Ty<'_>,
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"),
];
let path = match arms[1].pat.kind {
PatKind::TupleStruct(ref path, ref inner, _) => {
// Contains any non wildcard patterns (e.g., `Err(err)`)?
if !inner.iter().all(is_wild) {
return;
}
rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
},
PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => ident.to_string(),
PatKind::Path(ref path) => {
rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
},
_ => return,
};
for &(ty_path, pat_path) in candidates {
if path == *pat_path && match_type(cx, ty, ty_path) {
report_single_match_single_pattern(cx, ex, arms, expr, els);
}
}
}
fn check_match_bool(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(ref 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,
);
}
}
}
},
);
}
}
fn check_overlapping_arms<'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));
let type_ranges = type_ranges(&ranges);
if !type_ranges.is_empty() {
if let Some((start, end)) = overlapping(&type_ranges) {
span_lint_and_note(
cx,
MATCH_OVERLAPPING_ARM,
start.span,
"some ranges overlap",
Some(end.span),
"overlaps with this",
);
}
}
}
}
fn check_wild_err_arm(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
let ex_ty = cx.typeck_results().expr_ty(ex).peel_refs();
if is_type_diagnostic_item(cx, ex_ty, sym::result_type) {
for arm in arms {
if let PatKind::TupleStruct(ref path, ref 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 = String::from("_");
if !matching_wild {
// Looking for unused bindings (i.e.: `_e`)
inner.iter().for_each(|pat| {
if let PatKind::Binding(.., ident, None) = &pat.kind {
if ident.as_str().starts_with('_') && is_unused(ident, arm.body) {
ident_bind_name = (&ident.name.as_str()).to_string();
matching_wild = true;
}
}
});
}
if_chain! {
if matching_wild;
if let ExprKind::Block(ref block, _) = arm.body.kind;
if is_panic_block(block);
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",
);
}
}
}
}
}
}
}
fn check_wild_enum_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
let ty = cx.typeck_results().expr_ty(ex);
if !ty.is_enum() {
// If there isn't a nice closed set of possible values that can be conveniently enumerated,
// don't complain about not enumerating the mall.
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;
for arm in arms {
if let PatKind::Wild = arm.pat.kind {
wildcard_span = Some(arm.pat.span);
} else if let PatKind::Binding(_, _, ident, None) = arm.pat.kind {
wildcard_span = Some(arm.pat.span);
wildcard_ident = Some(ident);
}
}
if let Some(wildcard_span) = wildcard_span {
// Accumulate the variants which should be put in place of the wildcard because they're not
// already covered.
let mut missing_variants = vec![];
if let ty::Adt(def, _) = ty.kind() {
for variant in &def.variants {
missing_variants.push(variant);
}
}
for arm in arms {
if arm.guard.is_some() {
// 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.
continue;
}
if let PatKind::Path(ref path) = arm.pat.kind {
if let QPath::Resolved(_, p) = path {
missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
}
} else if let PatKind::TupleStruct(QPath::Resolved(_, p), ref patterns, ..) = arm.pat.kind {
// Some simple checks for exhaustive patterns.
// There is a room for improvements to detect more cases,
// but it can be more expensive to do so.
let is_pattern_exhaustive =
|pat: &&Pat<'_>| matches!(pat.kind, PatKind::Wild | PatKind::Binding(.., None));
if patterns.iter().all(is_pattern_exhaustive) {
missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
}
}
}
let mut suggestion: Vec<String> = missing_variants
.iter()
.map(|v| {
let suffix = match v.ctor_kind {
CtorKind::Fn => "(..)",
CtorKind::Const | CtorKind::Fictive => "",
};
let ident_str = if let Some(ident) = wildcard_ident {
format!("{} @ ", ident.name)
} else {
String::new()
};
// This path assumes that the enum type is imported into scope.
format!("{}{}{}", ident_str, cx.tcx.def_path_str(v.def_id), suffix)
})
.collect();
if suggestion.is_empty() {
return;
}
let mut message = "wildcard match will miss any future added variants";
if let ty::Adt(def, _) = ty.kind() {
if def.is_variant_list_non_exhaustive() {
message = "match on non-exhaustive enum doesn't explicitly match all known variants";
suggestion.push(String::from("_"));
}
}
if suggestion.len() == 1 {
// No need to check for non-exhaustive enum as in that case len would be greater than 1
span_lint_and_sugg(
cx,
MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
wildcard_span,
message,
"try this",
suggestion[0].clone(),
Applicability::MaybeIncorrect,
)
};
span_lint_and_sugg(
cx,
WILDCARD_ENUM_MATCH_ARM,
wildcard_span,
message,
"try this",
suggestion.join(" | "),
Applicability::MaybeIncorrect,
)
}
}
// If the block contains only a `panic!` macro (as expression or statement)
fn is_panic_block(block: &Block<'_>) -> bool {
match (&block.expr, block.stmts.len(), block.stmts.first()) {
(&Some(ref exp), 0, _) => {
is_expn_of(exp.span, "panic").is_some() && is_expn_of(exp.span, "unreachable").is_none()
},
(&None, 1, Some(stmt)) => {
is_expn_of(stmt.span, "panic").is_some() && is_expn_of(stmt.span, "unreachable").is_none()
},
_ => false,
}
}
fn check_match_ref_pats(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
if has_only_ref_pats(arms) {
let mut suggs = Vec::with_capacity(arms.len() + 1);
let (title, msg) = if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, ref inner) = ex.kind {
let span = ex.span.source_callsite();
suggs.push((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
(
"you don't need to add `&` to both the expression and the patterns",
"try",
)
} else {
let span = ex.span.source_callsite();
suggs.push((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
(
"you don't need to add `&` to all patterns",
"instead of prefixing all patterns with `&`, you can dereference the expression",
)
};
suggs.extend(arms.iter().filter_map(|a| {
if let PatKind::Ref(ref refp, _) = a.pat.kind {
Some((a.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, suggs);
}
});
}
}
fn check_match_as_ref(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(&arms[0]) {
is_ref_some_arm(&arms[1])
} else if is_none_arm(&arms[1]) {
is_ref_some_arm(&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,
)
}
}
}
fn check_wild_in_or_pats(cx: &LateContext<'_>, arms: &[Arm<'_>]) {
for arm in arms {
if let PatKind::Or(ref 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.",
);
}
}
}
}
/// Lint a `match` or `if let .. { .. } else { .. }` expr that could be replaced by `matches!`
fn check_match_like_matches<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
if let ExprKind::Match(ex, arms, ref match_source) = &expr.kind {
match match_source {
MatchSource::Normal => find_matches_sugg(cx, ex, arms, expr, false),
MatchSource::IfLetDesugar { .. } => find_matches_sugg(cx, ex, arms, expr, true),
_ => false,
}
} else {
false
}
}
/// Lint a `match` or desugared `if let` for replacement by `matches!`
fn find_matches_sugg(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>, desugared: bool) -> bool {
if_chain! {
if arms.len() >= 2;
if cx.typeck_results().expr_ty(expr).is_bool();
if let Some((b1_arm, b0_arms)) = arms.split_last();
if let Some(b0) = find_bool_lit(&b0_arms[0].body.kind, desugared);
if let Some(b1) = find_bool_lit(&b1_arm.body.kind, desugared);
if is_wild(&b1_arm.pat);
if b0 != b1;
let if_guard = &b0_arms[0].guard;
if if_guard.is_none() || b0_arms.len() == 1;
if b0_arms[0].attrs.is_empty();
if b0_arms[1..].iter()
.all(|arm| {
find_bool_lit(&arm.body.kind, desugared).map_or(false, |b| b == b0) &&
arm.guard.is_none() && arm.attrs.is_empty()
});
then {
// 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 _;
b0_arms.iter()
.map(|arm| snippet_with_applicability(cx, arm.pat.span, "..", &mut applicability))
.join(" | ")
};
let pat_and_guard = if let Some(Guard::If(g)) = if_guard {
format!("{} if {}", pat, snippet_with_applicability(cx, g.span, "..", &mut applicability))
} else {
pat
};
span_lint_and_sugg(
cx,
MATCH_LIKE_MATCHES_MACRO,
expr.span,
&format!("{} expression looks like `matches!` macro", if desugared { "if let .. else" } else { "match" }),
"try this",
format!(
"{}matches!({}, {})",
if b0 { "" } else { "!" },
snippet_with_applicability(cx, ex.span, "..", &mut applicability),
pat_and_guard,
),
applicability,
);
true
} else {
false
}
}
}
/// Extract a `bool` or `{ bool }`
fn find_bool_lit(ex: &ExprKind<'_>, desugared: bool) -> Option<bool> {
match ex {
ExprKind::Lit(Spanned {
node: LitKind::Bool(b), ..
}) => Some(*b),
ExprKind::Block(
rustc_hir::Block {
stmts: &[],
expr: Some(exp),
..
},
_,
) if desugared => {
if let ExprKind::Lit(Spanned {
node: LitKind::Bool(b), ..
}) = exp.kind
{
Some(b)
} else {
None
}
},
_ => None,
}
}
fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
if in_macro(expr.span) || 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 = remove_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);
}
};
(
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 => {
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>> {
if_chain! {
let map = &cx.tcx.hir();
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
}
/// Gets all arms that are unbounded `PatRange`s.
fn all_ranges<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>], ty: Ty<'tcx>) -> Vec<SpannedRange<Constant>> {
arms.iter()
.flat_map(|arm| {
if let Arm {
ref pat, guard: None, ..
} = *arm
{
if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
let lhs = match lhs {
Some(lhs) => constant(cx, cx.typeck_results(), lhs)?.0,
None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
};
let rhs = match rhs {
Some(rhs) => constant(cx, cx.typeck_results(), rhs)?.0,
None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
};
let rhs = match range_end {
RangeEnd::Included => Bound::Included(rhs),
RangeEnd::Excluded => Bound::Excluded(rhs),
};
return Some(SpannedRange {
span: pat.span,
node: (lhs, rhs),
});
}
if let PatKind::Lit(ref value) = pat.kind {
let value = constant(cx, cx.typeck_results(), value)?.0;
return Some(SpannedRange {
span: pat.span,
node: (value.clone(), Bound::Included(value)),
});
}
}
None
})
.collect()
}
#[derive(Debug, Eq, PartialEq)]
pub struct SpannedRange<T> {
pub span: Span,
pub node: (T, Bound<T>),
}
type TypedRanges = Vec<SpannedRange<u128>>;
/// Gets all `Int` ranges or all `Uint` ranges. Mixed types are an error anyway
/// and other types than
/// `Uint` and `Int` probably don't make sense.
fn type_ranges(ranges: &[SpannedRange<Constant>]) -> TypedRanges {
ranges
.iter()
.filter_map(|range| match range.node {
(Constant::Int(start), Bound::Included(Constant::Int(end))) => Some(SpannedRange {
span: range.span,
node: (start, Bound::Included(end)),
}),
(Constant::Int(start), Bound::Excluded(Constant::Int(end))) => Some(SpannedRange {
span: range.span,
node: (start, Bound::Excluded(end)),
}),
(Constant::Int(start), Bound::Unbounded) => Some(SpannedRange {
span: range.span,
node: (start, Bound::Unbounded),
}),
_ => None,
})
.collect()
}
fn is_unit_expr(expr: &Expr<'_>) -> bool {
match expr.kind {
ExprKind::Tup(ref v) if v.is_empty() => true,
ExprKind::Block(ref b, _) if b.stmts.is_empty() && b.expr.is_none() => true,
_ => false,
}
}
// Checks if arm has the form `None => None`
fn is_none_arm(arm: &Arm<'_>) -> bool {
matches!(arm.pat.kind, PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE))
}
// Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
fn is_ref_some_arm(arm: &Arm<'_>) -> Option<BindingAnnotation> {
if_chain! {
if let PatKind::TupleStruct(ref path, ref pats, _) = arm.pat.kind;
if pats.len() == 1 && match_qpath(path, &paths::OPTION_SOME);
if let PatKind::Binding(rb, .., ident, _) = pats[0].kind;
if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
if let ExprKind::Call(ref e, ref args) = remove_blocks(&arm.body).kind;
if let ExprKind::Path(ref some_path) = e.kind;
if match_qpath(some_path, &paths::OPTION_SOME) && args.len() == 1;
if let ExprKind::Path(QPath::Resolved(_, ref path2)) = args[0].kind;
if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
then {
return Some(rb)
}
}
None
}
fn has_only_ref_pats(arms: &[Arm<'_>]) -> bool {
let mapped = arms
.iter()
.map(|a| {
match a.pat.kind {
PatKind::Ref(..) => Some(true), // &-patterns
PatKind::Wild => Some(false), // an "anything" wildcard is also fine
_ => None, // any other pattern is not fine
}
})
.collect::<Option<Vec<bool>>>();
// look for Some(v) where there's at least one true element
mapped.map_or(false, |v| v.iter().any(|el| *el))
}
pub fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
where
T: Copy + Ord,
{
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
enum Kind<'a, T> {
Start(T, &'a SpannedRange<T>),
End(Bound<T>, &'a SpannedRange<T>),
}
impl<'a, T: Copy> Kind<'a, T> {
fn range(&self) -> &'a SpannedRange<T> {
match *self {
Kind::Start(_, r) | Kind::End(_, r) => r,
}
}
fn value(self) -> Bound<T> {
match self {
Kind::Start(t, _) => Bound::Included(t),
Kind::End(t, _) => t,
}
}
}
impl<'a, T: Copy + Ord> PartialOrd for Kind<'a, T> {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl<'a, T: Copy + Ord> Ord for Kind<'a, T> {
fn cmp(&self, other: &Self) -> Ordering {
match (self.value(), other.value()) {
(Bound::Included(a), Bound::Included(b)) | (Bound::Excluded(a), Bound::Excluded(b)) => a.cmp(&b),
// Range patterns cannot be unbounded (yet)
(Bound::Unbounded, _) | (_, Bound::Unbounded) => unimplemented!(),
(Bound::Included(a), Bound::Excluded(b)) => match a.cmp(&b) {
Ordering::Equal => Ordering::Greater,
other => other,
},
(Bound::Excluded(a), Bound::Included(b)) => match a.cmp(&b) {
Ordering::Equal => Ordering::Less,
other => other,
},
}
}
}
let mut values = Vec::with_capacity(2 * ranges.len());
for r in ranges {
values.push(Kind::Start(r.node.0, r));
values.push(Kind::End(r.node.1, r));
}
values.sort();
for (a, b) in values.iter().zip(values.iter().skip(1)) {
match (a, b) {
(&Kind::Start(_, ra), &Kind::End(_, rb)) => {
if ra.node != rb.node {
return Some((ra, rb));
}
},
(&Kind::End(a, _), &Kind::Start(b, _)) if a != Bound::Included(b) => (),
_ => return Some((a.range(), b.range())),
}
}
None
}
mod redundant_pattern_match {
use super::REDUNDANT_PATTERN_MATCHING;
use crate::utils::{match_qpath, match_trait_method, paths, snippet, span_lint_and_then};
use if_chain::if_chain;
use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
use rustc_hir::{Arm, Expr, ExprKind, MatchSource, PatKind, QPath};
use rustc_lint::LateContext;
use rustc_span::sym;
pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if let ExprKind::Match(op, arms, ref match_source) = &expr.kind {
match match_source {
MatchSource::Normal => find_sugg_for_match(cx, expr, op, arms),
MatchSource::IfLetDesugar { .. } => find_sugg_for_if_let(cx, expr, op, arms, "if"),
MatchSource::WhileLetDesugar => find_sugg_for_if_let(cx, expr, op, arms, "while"),
_ => {},
}
}
}
fn find_sugg_for_if_let<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'_>,
op: &Expr<'_>,
arms: &[Arm<'_>],
keyword: &'static str,
) {
let good_method = match arms[0].pat.kind {
PatKind::TupleStruct(ref path, ref patterns, _) if patterns.len() == 1 => {
if let PatKind::Wild = patterns[0].kind {
if match_qpath(path, &paths::RESULT_OK) {
"is_ok()"
} else if match_qpath(path, &paths::RESULT_ERR) {
"is_err()"
} else if match_qpath(path, &paths::OPTION_SOME) {
"is_some()"
} else if match_qpath(path, &paths::POLL_READY) {
"is_ready()"
} else if match_qpath(path, &paths::IPADDR_V4) {
"is_ipv4()"
} else if match_qpath(path, &paths::IPADDR_V6) {
"is_ipv6()"
} else {
return;
}
} else {
return;
}
},
PatKind::Path(ref path) => {
if match_qpath(path, &paths::OPTION_NONE) {
"is_none()"
} else if match_qpath(path, &paths::POLL_PENDING) {
"is_pending()"
} else {
return;
}
},
_ => return,
};
// check that `while_let_on_iterator` lint does not trigger
if_chain! {
if keyword == "while";
if let ExprKind::MethodCall(method_path, _, _, _) = op.kind;
if method_path.ident.name == sym::next;
if match_trait_method(cx, op, &paths::ITERATOR);
then {
return;
}
}
let result_expr = match &op.kind {
ExprKind::AddrOf(_, _, borrowed) => borrowed,
_ => op,
};
span_lint_and_then(
cx,
REDUNDANT_PATTERN_MATCHING,
arms[0].pat.span,
&format!("redundant pattern matching, consider using `{}`", good_method),
|diag| {
// while let ... = ... { ... }
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^
let expr_span = expr.span;
// while let ... = ... { ... }
// ^^^
let op_span = result_expr.span.source_callsite();
// while let ... = ... { ... }
// ^^^^^^^^^^^^^^^^^^^
let span = expr_span.until(op_span.shrink_to_hi());
diag.span_suggestion(
span,
"try this",
format!("{} {}.{}", keyword, snippet(cx, op_span, "_"), good_method),
Applicability::MachineApplicable, // snippet
);
},
);
}
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, ref patterns_left, _),
PatKind::TupleStruct(ref path_right, ref 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(
arms,
path_left,
path_right,
&paths::RESULT_OK,
&paths::RESULT_ERR,
"is_ok()",
"is_err()",
)
.or_else(|| {
find_good_method_for_match(
arms,
path_left,
path_right,
&paths::IPADDR_V4,
&paths::IPADDR_V6,
"is_ipv4()",
"is_ipv6()",
)
})
} else {
None
}
},
(PatKind::TupleStruct(ref path_left, ref patterns, _), PatKind::Path(ref path_right))
| (PatKind::Path(ref path_left), PatKind::TupleStruct(ref path_right, ref patterns, _))
if patterns.len() == 1 =>
{
if let PatKind::Wild = patterns[0].kind {
find_good_method_for_match(
arms,
path_left,
path_right,
&paths::OPTION_SOME,
&paths::OPTION_NONE,
"is_some()",
"is_none()",
)
.or_else(|| {
find_good_method_for_match(
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
);
},
);
}
}
}
fn find_good_method_for_match<'a>(
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 body_node_pair = if match_qpath(path_left, expected_left) && match_qpath(path_right, expected_right) {
(&(*arms[0].body).kind, &(*arms[1].body).kind)
} else if match_qpath(path_right, expected_left) && match_qpath(path_left, 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,
}
}
}
#[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, Bound::Included(4))]));
assert_eq!(
None,
overlapping(&[sp(1, Bound::Included(4)), sp(5, Bound::Included(6))])
);
assert_eq!(
None,
overlapping(&[
sp(1, Bound::Included(4)),
sp(5, Bound::Included(6)),
sp(10, Bound::Included(11))
],)
);
assert_eq!(
Some((&sp(1, Bound::Included(4)), &sp(3, Bound::Included(6)))),
overlapping(&[sp(1, Bound::Included(4)), sp(3, Bound::Included(6))])
);
assert_eq!(
Some((&sp(5, Bound::Included(6)), &sp(6, Bound::Included(11)))),
overlapping(&[
sp(1, Bound::Included(4)),
sp(5, Bound::Included(6)),
sp(6, Bound::Included(11))
],)
);
}
/// Implementation of `MATCH_SAME_ARMS`.
fn lint_match_arms<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) {
fn same_bindings<'tcx>(lhs: &FxHashMap<Symbol, Ty<'tcx>>, rhs: &FxHashMap<Symbol, Ty<'tcx>>) -> bool {
lhs.len() == rhs.len()
&& lhs
.iter()
.all(|(name, l_ty)| rhs.get(name).map_or(false, |r_ty| TyS::same_type(l_ty, r_ty)))
}
if let ExprKind::Match(_, ref 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);
// Arms with a guard are ignored, those cant 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).eq_expr(&lhs.body, &rhs.body) &&
// all patterns should have the same bindings
same_bindings(&bindings(cx, &lhs.pat), &bindings(cx, &rhs.pat))
};
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));
}
},
);
}
}
}
/// Returns the list of bindings in a pattern.
fn bindings<'tcx>(cx: &LateContext<'tcx>, pat: &Pat<'_>) -> FxHashMap<Symbol, Ty<'tcx>> {
fn bindings_impl<'tcx>(cx: &LateContext<'tcx>, pat: &Pat<'_>, map: &mut FxHashMap<Symbol, Ty<'tcx>>) {
match pat.kind {
PatKind::Box(ref pat) | PatKind::Ref(ref pat, _) => bindings_impl(cx, pat, map),
PatKind::TupleStruct(_, pats, _) => {
for pat in pats {
bindings_impl(cx, pat, map);
}
},
PatKind::Binding(.., ident, ref as_pat) => {
if let Entry::Vacant(v) = map.entry(ident.name) {
v.insert(cx.typeck_results().pat_ty(pat));
}
if let Some(ref as_pat) = *as_pat {
bindings_impl(cx, as_pat, map);
}
},
PatKind::Or(fields) | PatKind::Tuple(fields, _) => {
for pat in fields {
bindings_impl(cx, pat, map);
}
},
PatKind::Struct(_, fields, _) => {
for pat in fields {
bindings_impl(cx, &pat.pat, map);
}
},
PatKind::Slice(lhs, ref mid, rhs) => {
for pat in lhs {
bindings_impl(cx, pat, map);
}
if let Some(ref mid) = *mid {
bindings_impl(cx, mid, map);
}
for pat in rhs {
bindings_impl(cx, pat, map);
}
},
PatKind::Lit(..) | PatKind::Range(..) | PatKind::Wild | PatKind::Path(..) => (),
}
}
let mut result = FxHashMap::default();
bindings_impl(cx, pat, &mut result);
result
}