[rustc.git] / src / tools / clippy / clippy_lints / src / eq_op.rs

use clippy_utils::diagnostics::{multispan_sugg, span_lint, span_lint_and_then};
use clippy_utils::source::snippet;
use clippy_utils::ty::{implements_trait, is_copy};
use clippy_utils::{
    ast_utils::is_useless_with_eq_exprs, eq_expr_value, higher, in_macro, is_expn_of, is_in_test_function,
};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{BinOpKind, BorrowKind, Expr, ExprKind, StmtKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};

declare_clippy_lint! {
    /// ### What it does
    /// Checks for equal operands to comparison, logical and
    /// bitwise, difference and division binary operators (`==`, `>`, etc., `&&`,
    /// `||`, `&`, `|`, `^`, `-` and `/`).
    ///
    /// ### Why is this bad?
    /// This is usually just a typo or a copy and paste error.
    ///
    /// ### Known problems
    /// False negatives: We had some false positives regarding
    /// calls (notably [racer](https://github.com/phildawes/racer) had one instance
    /// of `x.pop() && x.pop()`), so we removed matching any function or method
    /// calls. We may introduce a list of known pure functions in the future.
    ///
    /// ### Example
    /// ```rust
    /// # let x = 1;
    /// if x + 1 == x + 1 {}
    /// ```
    /// or
    /// ```rust
    /// # let a = 3;
    /// # let b = 4;
    /// assert_eq!(a, a);
    /// ```
    pub EQ_OP,
    correctness,
    "equal operands on both sides of a comparison or bitwise combination (e.g., `x == x`)"
}

declare_clippy_lint! {
    /// ### What it does
    /// Checks for arguments to `==` which have their address
    /// taken to satisfy a bound
    /// and suggests to dereference the other argument instead
    ///
    /// ### Why is this bad?
    /// It is more idiomatic to dereference the other argument.
    ///
    /// ### Known problems
    /// None
    ///
    /// ### Example
    /// ```ignore
    /// // Bad
    /// &x == y
    ///
    /// // Good
    /// x == *y
    /// ```
    pub OP_REF,
    style,
    "taking a reference to satisfy the type constraints on `==`"
}

declare_lint_pass!(EqOp => [EQ_OP, OP_REF]);

const ASSERT_MACRO_NAMES: [&str; 4] = ["assert_eq", "assert_ne", "debug_assert_eq", "debug_assert_ne"];

impl<'tcx> LateLintPass<'tcx> for EqOp {
    #[allow(clippy::similar_names, clippy::too_many_lines)]
    fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
        if let ExprKind::Block(block, _) = e.kind {
            for stmt in block.stmts {
                for amn in &ASSERT_MACRO_NAMES {
                    if_chain! {
                        if is_expn_of(stmt.span, amn).is_some();
                        if let StmtKind::Semi(matchexpr) = stmt.kind;
                        if let Some(macro_args) = higher::extract_assert_macro_args(matchexpr);
                        if macro_args.len() == 2;
                        let (lhs, rhs) = (macro_args[0], macro_args[1]);
                        if eq_expr_value(cx, lhs, rhs);
                        if !is_in_test_function(cx.tcx, e.hir_id);
                        then {
                            span_lint(
                                cx,
                                EQ_OP,
                                lhs.span.to(rhs.span),
                                &format!("identical args used in this `{}!` macro call", amn),
                            );
                        }
                    }
                }
            }
        }
        if let ExprKind::Binary(op, left, right) = e.kind {
            if e.span.from_expansion() {
                return;
            }
            let macro_with_not_op = |expr_kind: &ExprKind<'_>| {
                if let ExprKind::Unary(_, expr) = *expr_kind {
                    in_macro(expr.span)
                } else {
                    false
                }
            };
            if macro_with_not_op(&left.kind) || macro_with_not_op(&right.kind) {
                return;
            }
            if is_useless_with_eq_exprs(op.node.into())
                && eq_expr_value(cx, left, right)
                && !is_in_test_function(cx.tcx, e.hir_id)
            {
                span_lint(
                    cx,
                    EQ_OP,
                    e.span,
                    &format!("equal expressions as operands to `{}`", op.node.as_str()),
                );
                return;
            }
            let (trait_id, requires_ref) = match op.node {
                BinOpKind::Add => (cx.tcx.lang_items().add_trait(), false),
                BinOpKind::Sub => (cx.tcx.lang_items().sub_trait(), false),
                BinOpKind::Mul => (cx.tcx.lang_items().mul_trait(), false),
                BinOpKind::Div => (cx.tcx.lang_items().div_trait(), false),
                BinOpKind::Rem => (cx.tcx.lang_items().rem_trait(), false),
                // don't lint short circuiting ops
                BinOpKind::And | BinOpKind::Or => return,
                BinOpKind::BitXor => (cx.tcx.lang_items().bitxor_trait(), false),
                BinOpKind::BitAnd => (cx.tcx.lang_items().bitand_trait(), false),
                BinOpKind::BitOr => (cx.tcx.lang_items().bitor_trait(), false),
                BinOpKind::Shl => (cx.tcx.lang_items().shl_trait(), false),
                BinOpKind::Shr => (cx.tcx.lang_items().shr_trait(), false),
                BinOpKind::Ne | BinOpKind::Eq => (cx.tcx.lang_items().eq_trait(), true),
                BinOpKind::Lt | BinOpKind::Le | BinOpKind::Ge | BinOpKind::Gt => {
                    (cx.tcx.lang_items().partial_ord_trait(), true)
                },
            };
            if let Some(trait_id) = trait_id {
                #[allow(clippy::match_same_arms)]
                match (&left.kind, &right.kind) {
                    // do not suggest to dereference literals
                    (&ExprKind::Lit(..), _) | (_, &ExprKind::Lit(..)) => {},
                    // &foo == &bar
                    (&ExprKind::AddrOf(BorrowKind::Ref, _, l), &ExprKind::AddrOf(BorrowKind::Ref, _, r)) => {
                        let lty = cx.typeck_results().expr_ty(l);
                        let rty = cx.typeck_results().expr_ty(r);
                        let lcpy = is_copy(cx, lty);
                        let rcpy = is_copy(cx, rty);
                        // either operator autorefs or both args are copyable
                        if (requires_ref || (lcpy && rcpy)) && implements_trait(cx, lty, trait_id, &[rty.into()]) {
                            span_lint_and_then(
                                cx,
                                OP_REF,
                                e.span,
                                "needlessly taken reference of both operands",
                                |diag| {
                                    let lsnip = snippet(cx, l.span, "...").to_string();
                                    let rsnip = snippet(cx, r.span, "...").to_string();
                                    multispan_sugg(
                                        diag,
                                        "use the values directly",
                                        vec![(left.span, lsnip), (right.span, rsnip)],
                                    );
                                },
                            );
                        } else if lcpy
                            && !rcpy
                            && implements_trait(cx, lty, trait_id, &[cx.typeck_results().expr_ty(right).into()])
                        {
                            span_lint_and_then(
                                cx,
                                OP_REF,
                                e.span,
                                "needlessly taken reference of left operand",
                                |diag| {
                                    let lsnip = snippet(cx, l.span, "...").to_string();
                                    diag.span_suggestion(
                                        left.span,
                                        "use the left value directly",
                                        lsnip,
                                        Applicability::MaybeIncorrect, // FIXME #2597
                                    );
                                },
                            );
                        } else if !lcpy
                            && rcpy
                            && implements_trait(cx, cx.typeck_results().expr_ty(left), trait_id, &[rty.into()])
                        {
                            span_lint_and_then(
                                cx,
                                OP_REF,
                                e.span,
                                "needlessly taken reference of right operand",
                                |diag| {
                                    let rsnip = snippet(cx, r.span, "...").to_string();
                                    diag.span_suggestion(
                                        right.span,
                                        "use the right value directly",
                                        rsnip,
                                        Applicability::MaybeIncorrect, // FIXME #2597
                                    );
                                },
                            );
                        }
                    },
                    // &foo == bar
                    (&ExprKind::AddrOf(BorrowKind::Ref, _, l), _) => {
                        let lty = cx.typeck_results().expr_ty(l);
                        let lcpy = is_copy(cx, lty);
                        if (requires_ref || lcpy)
                            && implements_trait(cx, lty, trait_id, &[cx.typeck_results().expr_ty(right).into()])
                        {
                            span_lint_and_then(
                                cx,
                                OP_REF,
                                e.span,
                                "needlessly taken reference of left operand",
                                |diag| {
                                    let lsnip = snippet(cx, l.span, "...").to_string();
                                    diag.span_suggestion(
                                        left.span,
                                        "use the left value directly",
                                        lsnip,
                                        Applicability::MaybeIncorrect, // FIXME #2597
                                    );
                                },
                            );
                        }
                    },
                    // foo == &bar
                    (_, &ExprKind::AddrOf(BorrowKind::Ref, _, r)) => {
                        let rty = cx.typeck_results().expr_ty(r);
                        let rcpy = is_copy(cx, rty);
                        if (requires_ref || rcpy)
                            && implements_trait(cx, cx.typeck_results().expr_ty(left), trait_id, &[rty.into()])
                        {
                            span_lint_and_then(cx, OP_REF, e.span, "taken reference of right operand", |diag| {
                                let rsnip = snippet(cx, r.span, "...").to_string();
                                diag.span_suggestion(
                                    right.span,
                                    "use the right value directly",
                                    rsnip,
                                    Applicability::MaybeIncorrect, // FIXME #2597
                                );
                            });
                        }
                    },
                    _ => {},
                }
            }
        }
    }
}
Commit	Line	Data
cdc7bbd5 XL	1	use clippy_utils::diagnostics::{multispan_sugg, span_lint, span_lint_and_then};
	2	use clippy_utils::source::snippet;
	3	use clippy_utils::ty::{implements_trait, is_copy};
3c0e092e XL	4	use clippy_utils::{
	5	ast_utils::is_useless_with_eq_exprs, eq_expr_value, higher, in_macro, is_expn_of, is_in_test_function,
	6	};
f20569fa XL	7	use if_chain::if_chain;
	8	use rustc_errors::Applicability;
	9	use rustc_hir::{BinOpKind, BorrowKind, Expr, ExprKind, StmtKind};
	10	use rustc_lint::{LateContext, LateLintPass};
	11	use rustc_session::{declare_lint_pass, declare_tool_lint};
	12
	13	declare_clippy_lint! {
94222f64 XL	14	/// ### What it does
94222f64 XL	15	/// Checks for equal operands to comparison, logical and
f20569fa XL	16	/// bitwise, difference and division binary operators (`==`, `>`, etc., `&&`,
	17	/// `\|\|`, `&`, `\|`, `^`, `-` and `/`).
	18	///
94222f64 XL	19	/// ### Why is this bad?
94222f64 XL	20	/// This is usually just a typo or a copy and paste error.
f20569fa	21	///
94222f64 XL	22	/// ### Known problems
94222f64 XL	23	/// False negatives: We had some false positives regarding
f20569fa XL	24	/// calls (notably [racer](https://github.com/phildawes/racer) had one instance
	25	/// of `x.pop() && x.pop()`), so we removed matching any function or method
	26	/// calls. We may introduce a list of known pure functions in the future.
	27	///
94222f64	28	/// ### Example
f20569fa XL	29	/// ```rust
	30	/// # let x = 1;
	31	/// if x + 1 == x + 1 {}
	32	/// ```
	33	/// or
	34	/// ```rust
	35	/// # let a = 3;
	36	/// # let b = 4;
	37	/// assert_eq!(a, a);
	38	/// ```
	39	pub EQ_OP,
	40	correctness,
	41	"equal operands on both sides of a comparison or bitwise combination (e.g., `x == x`)"
	42	}
	43
	44	declare_clippy_lint! {
94222f64 XL	45	/// ### What it does
94222f64 XL	46	/// Checks for arguments to `==` which have their address
f20569fa XL	47	/// taken to satisfy a bound
	48	/// and suggests to dereference the other argument instead
	49	///
94222f64 XL	50	/// ### Why is this bad?
94222f64 XL	51	/// It is more idiomatic to dereference the other argument.
f20569fa	52	///
94222f64 XL	53	/// ### Known problems
94222f64 XL	54	/// None
f20569fa	55	///
94222f64	56	/// ### Example
f20569fa XL	57	/// ```ignore
	58	/// // Bad
	59	/// &x == y
	60	///
	61	/// // Good
	62	/// x == *y
	63	/// ```
	64	pub OP_REF,
	65	style,
	66	"taking a reference to satisfy the type constraints on `==`"
	67	}
	68
	69	declare_lint_pass!(EqOp => [EQ_OP, OP_REF]);
	70
	71	const ASSERT_MACRO_NAMES: [&str; 4] = ["assert_eq", "assert_ne", "debug_assert_eq", "debug_assert_ne"];
	72
	73	impl<'tcx> LateLintPass<'tcx> for EqOp {
	74	#[allow(clippy::similar_names, clippy::too_many_lines)]
	75	fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
cdc7bbd5	76	if let ExprKind::Block(block, _) = e.kind {
f20569fa XL	77	for stmt in block.stmts {
	78	for amn in &ASSERT_MACRO_NAMES {
	79	if_chain! {
	80	if is_expn_of(stmt.span, amn).is_some();
cdc7bbd5	81	if let StmtKind::Semi(matchexpr) = stmt.kind;
f20569fa XL	82	if let Some(macro_args) = higher::extract_assert_macro_args(matchexpr);
	83	if macro_args.len() == 2;
	84	let (lhs, rhs) = (macro_args[0], macro_args[1]);
	85	if eq_expr_value(cx, lhs, rhs);
3c0e092e	86	if !is_in_test_function(cx.tcx, e.hir_id);
f20569fa XL	87	then {
	88	span_lint(
	89	cx,
	90	EQ_OP,
	91	lhs.span.to(rhs.span),
	92	&format!("identical args used in this `{}!` macro call", amn),
	93	);
	94	}
	95	}
	96	}
	97	}
	98	}
cdc7bbd5	99	if let ExprKind::Binary(op, left, right) = e.kind {
f20569fa XL	100	if e.span.from_expansion() {
	101	return;
	102	}
	103	let macro_with_not_op = \|expr_kind: &ExprKind<'_>\| {
cdc7bbd5	104	if let ExprKind::Unary(_, expr) = *expr_kind {
f20569fa XL	105	in_macro(expr.span)
	106	} else {
	107	false
	108	}
	109	};
	110	if macro_with_not_op(&left.kind) \|\| macro_with_not_op(&right.kind) {
	111	return;
	112	}
3c0e092e XL	113	if is_useless_with_eq_exprs(op.node.into())
	114	&& eq_expr_value(cx, left, right)
	115	&& !is_in_test_function(cx.tcx, e.hir_id)
	116	{
f20569fa XL	117	span_lint(
	118	cx,
	119	EQ_OP,
	120	e.span,
	121	&format!("equal expressions as operands to `{}`", op.node.as_str()),
	122	);
	123	return;
	124	}
	125	let (trait_id, requires_ref) = match op.node {
	126	BinOpKind::Add => (cx.tcx.lang_items().add_trait(), false),
	127	BinOpKind::Sub => (cx.tcx.lang_items().sub_trait(), false),
	128	BinOpKind::Mul => (cx.tcx.lang_items().mul_trait(), false),
	129	BinOpKind::Div => (cx.tcx.lang_items().div_trait(), false),
	130	BinOpKind::Rem => (cx.tcx.lang_items().rem_trait(), false),
	131	// don't lint short circuiting ops
	132	BinOpKind::And \| BinOpKind::Or => return,
	133	BinOpKind::BitXor => (cx.tcx.lang_items().bitxor_trait(), false),
	134	BinOpKind::BitAnd => (cx.tcx.lang_items().bitand_trait(), false),
	135	BinOpKind::BitOr => (cx.tcx.lang_items().bitor_trait(), false),
	136	BinOpKind::Shl => (cx.tcx.lang_items().shl_trait(), false),
	137	BinOpKind::Shr => (cx.tcx.lang_items().shr_trait(), false),
	138	BinOpKind::Ne \| BinOpKind::Eq => (cx.tcx.lang_items().eq_trait(), true),
	139	BinOpKind::Lt \| BinOpKind::Le \| BinOpKind::Ge \| BinOpKind::Gt => {
	140	(cx.tcx.lang_items().partial_ord_trait(), true)
	141	},
	142	};
	143	if let Some(trait_id) = trait_id {
	144	#[allow(clippy::match_same_arms)]
	145	match (&left.kind, &right.kind) {
	146	// do not suggest to dereference literals
	147	(&ExprKind::Lit(..), _) \| (_, &ExprKind::Lit(..)) => {},
	148	// &foo == &bar
cdc7bbd5	149	(&ExprKind::AddrOf(BorrowKind::Ref, _, l), &ExprKind::AddrOf(BorrowKind::Ref, _, r)) => {
f20569fa XL	150	let lty = cx.typeck_results().expr_ty(l);
	151	let rty = cx.typeck_results().expr_ty(r);
	152	let lcpy = is_copy(cx, lty);
	153	let rcpy = is_copy(cx, rty);
	154	// either operator autorefs or both args are copyable
	155	if (requires_ref \|\| (lcpy && rcpy)) && implements_trait(cx, lty, trait_id, &[rty.into()]) {
	156	span_lint_and_then(
	157	cx,
	158	OP_REF,
	159	e.span,
	160	"needlessly taken reference of both operands",
	161	\|diag\| {
	162	let lsnip = snippet(cx, l.span, "...").to_string();
	163	let rsnip = snippet(cx, r.span, "...").to_string();
	164	multispan_sugg(
	165	diag,
	166	"use the values directly",
	167	vec![(left.span, lsnip), (right.span, rsnip)],
	168	);
	169	},
17df50a5	170	);
f20569fa XL	171	} else if lcpy
	172	&& !rcpy
	173	&& implements_trait(cx, lty, trait_id, &[cx.typeck_results().expr_ty(right).into()])
	174	{
	175	span_lint_and_then(
	176	cx,
	177	OP_REF,
	178	e.span,
	179	"needlessly taken reference of left operand",
	180	\|diag\| {
	181	let lsnip = snippet(cx, l.span, "...").to_string();
	182	diag.span_suggestion(
	183	left.span,
	184	"use the left value directly",
	185	lsnip,
	186	Applicability::MaybeIncorrect, // FIXME #2597
	187	);
	188	},
17df50a5	189	);
f20569fa XL	190	} else if !lcpy
	191	&& rcpy
	192	&& implements_trait(cx, cx.typeck_results().expr_ty(left), trait_id, &[rty.into()])
	193	{
	194	span_lint_and_then(
	195	cx,
	196	OP_REF,
	197	e.span,
	198	"needlessly taken reference of right operand",
	199	\|diag\| {
	200	let rsnip = snippet(cx, r.span, "...").to_string();
	201	diag.span_suggestion(
	202	right.span,
	203	"use the right value directly",
	204	rsnip,
	205	Applicability::MaybeIncorrect, // FIXME #2597
	206	);
	207	},
17df50a5	208	);
f20569fa XL	209	}
	210	},
	211	// &foo == bar
cdc7bbd5	212	(&ExprKind::AddrOf(BorrowKind::Ref, _, l), _) => {
f20569fa XL	213	let lty = cx.typeck_results().expr_ty(l);
	214	let lcpy = is_copy(cx, lty);
	215	if (requires_ref \|\| lcpy)
	216	&& implements_trait(cx, lty, trait_id, &[cx.typeck_results().expr_ty(right).into()])
	217	{
	218	span_lint_and_then(
	219	cx,
	220	OP_REF,
	221	e.span,
	222	"needlessly taken reference of left operand",
	223	\|diag\| {
	224	let lsnip = snippet(cx, l.span, "...").to_string();
	225	diag.span_suggestion(
	226	left.span,
	227	"use the left value directly",
	228	lsnip,
	229	Applicability::MaybeIncorrect, // FIXME #2597
	230	);
	231	},
17df50a5	232	);
f20569fa XL	233	}
	234	},
	235	// foo == &bar
cdc7bbd5	236	(_, &ExprKind::AddrOf(BorrowKind::Ref, _, r)) => {
f20569fa XL	237	let rty = cx.typeck_results().expr_ty(r);
	238	let rcpy = is_copy(cx, rty);
	239	if (requires_ref \|\| rcpy)
	240	&& implements_trait(cx, cx.typeck_results().expr_ty(left), trait_id, &[rty.into()])
	241	{
	242	span_lint_and_then(cx, OP_REF, e.span, "taken reference of right operand", \|diag\| {
	243	let rsnip = snippet(cx, r.span, "...").to_string();
	244	diag.span_suggestion(
	245	right.span,
	246	"use the right value directly",
	247	rsnip,
	248	Applicability::MaybeIncorrect, // FIXME #2597
	249	);
17df50a5	250	});
f20569fa XL	251	}
	252	},
	253	_ => {},
	254	}
	255	}
	256	}
	257	}
	258	}