mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-22 11:03:16 +00:00
171 lines
6 KiB
Rust
171 lines
6 KiB
Rust
//! lint on blocks unnecessarily using >= with a + 1 or - 1
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use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::source::snippet_opt;
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use rustc_ast::ast::{BinOpKind, Expr, ExprKind, Lit, LitKind};
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use rustc_errors::Applicability;
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use rustc_lint::{EarlyContext, EarlyLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for usage of `x >= y + 1` or `x - 1 >= y` (and `<=`) in a block
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///
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/// ### Why is this bad?
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/// Readability -- better to use `> y` instead of `>= y + 1`.
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///
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/// ### Example
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/// ```rust
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/// # let x = 1;
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/// # let y = 1;
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/// if x >= y + 1 {}
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/// ```
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///
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/// Could be written as:
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///
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/// ```rust
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/// # let x = 1;
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/// # let y = 1;
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/// if x > y {}
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/// ```
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pub INT_PLUS_ONE,
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complexity,
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"instead of using `x >= y + 1`, use `x > y`"
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}
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declare_lint_pass!(IntPlusOne => [INT_PLUS_ONE]);
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// cases:
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// BinOpKind::Ge
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// x >= y + 1
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// x - 1 >= y
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//
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// BinOpKind::Le
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// x + 1 <= y
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// x <= y - 1
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#[derive(Copy, Clone)]
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enum Side {
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Lhs,
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Rhs,
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}
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impl IntPlusOne {
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#[allow(clippy::cast_sign_loss)]
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fn check_lit(lit: &Lit, target_value: i128) -> bool {
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if let LitKind::Int(value, ..) = lit.kind {
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return value == (target_value as u128);
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}
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false
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}
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fn check_binop(cx: &EarlyContext<'_>, binop: BinOpKind, lhs: &Expr, rhs: &Expr) -> Option<String> {
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match (binop, &lhs.kind, &rhs.kind) {
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// case where `x - 1 >= ...` or `-1 + x >= ...`
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(BinOpKind::Ge, &ExprKind::Binary(ref lhskind, ref lhslhs, ref lhsrhs), _) => {
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match (lhskind.node, &lhslhs.kind, &lhsrhs.kind) {
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// `-1 + x`
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(BinOpKind::Add, &ExprKind::Lit(ref lit), _) if Self::check_lit(lit, -1) => {
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Self::generate_recommendation(cx, binop, lhsrhs, rhs, Side::Lhs)
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},
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// `x - 1`
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(BinOpKind::Sub, _, &ExprKind::Lit(ref lit)) if Self::check_lit(lit, 1) => {
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Self::generate_recommendation(cx, binop, lhslhs, rhs, Side::Lhs)
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},
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_ => None,
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}
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},
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// case where `... >= y + 1` or `... >= 1 + y`
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(BinOpKind::Ge, _, &ExprKind::Binary(ref rhskind, ref rhslhs, ref rhsrhs))
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if rhskind.node == BinOpKind::Add =>
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{
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match (&rhslhs.kind, &rhsrhs.kind) {
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// `y + 1` and `1 + y`
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(&ExprKind::Lit(ref lit), _) if Self::check_lit(lit, 1) => {
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Self::generate_recommendation(cx, binop, rhsrhs, lhs, Side::Rhs)
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},
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(_, &ExprKind::Lit(ref lit)) if Self::check_lit(lit, 1) => {
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Self::generate_recommendation(cx, binop, rhslhs, lhs, Side::Rhs)
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},
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_ => None,
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}
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}
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// case where `x + 1 <= ...` or `1 + x <= ...`
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(BinOpKind::Le, &ExprKind::Binary(ref lhskind, ref lhslhs, ref lhsrhs), _)
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if lhskind.node == BinOpKind::Add =>
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{
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match (&lhslhs.kind, &lhsrhs.kind) {
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// `1 + x` and `x + 1`
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(&ExprKind::Lit(ref lit), _) if Self::check_lit(lit, 1) => {
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Self::generate_recommendation(cx, binop, lhsrhs, rhs, Side::Lhs)
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},
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(_, &ExprKind::Lit(ref lit)) if Self::check_lit(lit, 1) => {
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Self::generate_recommendation(cx, binop, lhslhs, rhs, Side::Lhs)
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},
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_ => None,
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}
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}
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// case where `... >= y - 1` or `... >= -1 + y`
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(BinOpKind::Le, _, &ExprKind::Binary(ref rhskind, ref rhslhs, ref rhsrhs)) => {
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match (rhskind.node, &rhslhs.kind, &rhsrhs.kind) {
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// `-1 + y`
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(BinOpKind::Add, &ExprKind::Lit(ref lit), _) if Self::check_lit(lit, -1) => {
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Self::generate_recommendation(cx, binop, rhsrhs, lhs, Side::Rhs)
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},
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// `y - 1`
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(BinOpKind::Sub, _, &ExprKind::Lit(ref lit)) if Self::check_lit(lit, 1) => {
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Self::generate_recommendation(cx, binop, rhslhs, lhs, Side::Rhs)
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},
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_ => None,
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}
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},
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_ => None,
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}
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}
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fn generate_recommendation(
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cx: &EarlyContext<'_>,
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binop: BinOpKind,
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node: &Expr,
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other_side: &Expr,
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side: Side,
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) -> Option<String> {
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let binop_string = match binop {
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BinOpKind::Ge => ">",
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BinOpKind::Le => "<",
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_ => return None,
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};
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if let Some(snippet) = snippet_opt(cx, node.span) {
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if let Some(other_side_snippet) = snippet_opt(cx, other_side.span) {
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let rec = match side {
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Side::Lhs => Some(format!("{} {} {}", snippet, binop_string, other_side_snippet)),
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Side::Rhs => Some(format!("{} {} {}", other_side_snippet, binop_string, snippet)),
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};
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return rec;
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}
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}
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None
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}
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fn emit_warning(cx: &EarlyContext<'_>, block: &Expr, recommendation: String) {
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span_lint_and_sugg(
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cx,
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INT_PLUS_ONE,
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block.span,
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"unnecessary `>= y + 1` or `x - 1 >=`",
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"change it to",
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recommendation,
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Applicability::MachineApplicable, // snippet
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);
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}
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}
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impl EarlyLintPass for IntPlusOne {
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fn check_expr(&mut self, cx: &EarlyContext<'_>, item: &Expr) {
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if let ExprKind::Binary(ref kind, ref lhs, ref rhs) = item.kind {
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if let Some(rec) = Self::check_binop(cx, kind.node, lhs, rhs) {
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Self::emit_warning(cx, item, rec);
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}
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}
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}
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}
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