mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-22 19:13:29 +00:00
275 lines
9.5 KiB
Rust
275 lines
9.5 KiB
Rust
// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use crate::rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass};
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use crate::rustc::{declare_tool_lint, lint_array};
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use crate::syntax::ast;
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use crate::syntax::ptr::P;
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use crate::utils::{differing_macro_contexts, in_macro, snippet_opt, span_note_and_lint};
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/// **What it does:** Checks for use of the non-existent `=*`, `=!` and `=-`
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/// operators.
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///
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/// **Why is this bad?** This is either a typo of `*=`, `!=` or `-=` or
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/// confusing.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust,ignore
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/// a =- 42; // confusing, should it be `a -= 42` or `a = -42`?
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/// ```
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declare_clippy_lint! {
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pub SUSPICIOUS_ASSIGNMENT_FORMATTING,
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style,
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"suspicious formatting of `*=`, `-=` or `!=`"
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}
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/// **What it does:** Checks for formatting of `else`. It lints if the `else`
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/// is followed immediately by a newline or the `else` seems to be missing.
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///
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/// **Why is this bad?** This is probably some refactoring remnant, even if the
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/// code is correct, it might look confusing.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust,ignore
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/// if foo {
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/// } { // looks like an `else` is missing here
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/// }
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///
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/// if foo {
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/// } if bar { // looks like an `else` is missing here
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/// }
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///
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/// if foo {
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/// } else
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///
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/// { // this is the `else` block of the previous `if`, but should it be?
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/// }
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///
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/// if foo {
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/// } else
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///
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/// if bar { // this is the `else` block of the previous `if`, but should it be?
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/// }
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/// ```
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declare_clippy_lint! {
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pub SUSPICIOUS_ELSE_FORMATTING,
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style,
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"suspicious formatting of `else`"
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}
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/// **What it does:** Checks for possible missing comma in an array. It lints if
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/// an array element is a binary operator expression and it lies on two lines.
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///
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/// **Why is this bad?** This could lead to unexpected results.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust,ignore
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/// let a = &[
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/// -1, -2, -3 // <= no comma here
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/// -4, -5, -6
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/// ];
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/// ```
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declare_clippy_lint! {
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pub POSSIBLE_MISSING_COMMA,
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correctness,
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"possible missing comma in array"
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}
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#[derive(Copy, Clone)]
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pub struct Formatting;
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impl LintPass for Formatting {
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fn get_lints(&self) -> LintArray {
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lint_array!(
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SUSPICIOUS_ASSIGNMENT_FORMATTING,
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SUSPICIOUS_ELSE_FORMATTING,
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POSSIBLE_MISSING_COMMA
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)
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}
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}
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impl EarlyLintPass for Formatting {
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fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
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for w in block.stmts.windows(2) {
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match (&w[0].node, &w[1].node) {
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(&ast::StmtKind::Expr(ref first), &ast::StmtKind::Expr(ref second))
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| (&ast::StmtKind::Expr(ref first), &ast::StmtKind::Semi(ref second)) => {
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check_missing_else(cx, first, second);
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},
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_ => (),
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}
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}
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}
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fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
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check_assign(cx, expr);
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check_else(cx, expr);
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check_array(cx, expr);
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}
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}
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/// Implementation of the `SUSPICIOUS_ASSIGNMENT_FORMATTING` lint.
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fn check_assign(cx: &EarlyContext<'_>, expr: &ast::Expr) {
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if let ast::ExprKind::Assign(ref lhs, ref rhs) = expr.node {
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if !differing_macro_contexts(lhs.span, rhs.span) && !in_macro(lhs.span) {
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let eq_span = lhs.span.between(rhs.span);
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if let ast::ExprKind::Unary(op, ref sub_rhs) = rhs.node {
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if let Some(eq_snippet) = snippet_opt(cx, eq_span) {
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let op = ast::UnOp::to_string(op);
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let eqop_span = lhs.span.between(sub_rhs.span);
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if eq_snippet.ends_with('=') {
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span_note_and_lint(
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cx,
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SUSPICIOUS_ASSIGNMENT_FORMATTING,
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eqop_span,
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&format!(
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"this looks like you are trying to use `.. {op}= ..`, but you \
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really are doing `.. = ({op} ..)`",
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op = op
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),
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eqop_span,
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&format!("to remove this lint, use either `{op}=` or `= {op}`", op = op),
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);
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}
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}
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}
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}
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}
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}
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/// Implementation of the `SUSPICIOUS_ELSE_FORMATTING` lint for weird `else`.
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fn check_else(cx: &EarlyContext<'_>, expr: &ast::Expr) {
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if let Some((then, &Some(ref else_))) = unsugar_if(expr) {
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if (is_block(else_) || unsugar_if(else_).is_some())
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&& !differing_macro_contexts(then.span, else_.span)
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&& !in_macro(then.span)
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{
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// workaround for rust-lang/rust#43081
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if expr.span.lo().0 == 0 && expr.span.hi().0 == 0 {
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return;
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}
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// this will be a span from the closing ‘}’ of the “then” block (excluding) to
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// the
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// “if” of the “else if” block (excluding)
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let else_span = then.span.between(else_.span);
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// the snippet should look like " else \n " with maybe comments anywhere
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// it’s bad when there is a ‘\n’ after the “else”
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if let Some(else_snippet) = snippet_opt(cx, else_span) {
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let else_pos = else_snippet.find("else").expect("there must be a `else` here");
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if else_snippet[else_pos..].contains('\n') {
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let else_desc = if unsugar_if(else_).is_some() { "if" } else { "{..}" };
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span_note_and_lint(
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cx,
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SUSPICIOUS_ELSE_FORMATTING,
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else_span,
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&format!("this is an `else {}` but the formatting might hide it", else_desc),
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else_span,
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&format!(
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"to remove this lint, remove the `else` or remove the new line between \
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`else` and `{}`",
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else_desc,
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),
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);
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}
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}
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}
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}
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}
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fn has_unary_equivalent(bin_op: ast::BinOpKind) -> bool {
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// &, *, -
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bin_op == ast::BinOpKind::And || bin_op == ast::BinOpKind::Mul || bin_op == ast::BinOpKind::Sub
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}
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/// Implementation of the `POSSIBLE_MISSING_COMMA` lint for array
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fn check_array(cx: &EarlyContext<'_>, expr: &ast::Expr) {
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if let ast::ExprKind::Array(ref array) = expr.node {
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for element in array {
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if let ast::ExprKind::Binary(ref op, ref lhs, _) = element.node {
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if has_unary_equivalent(op.node) && !differing_macro_contexts(lhs.span, op.span) {
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let space_span = lhs.span.between(op.span);
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if let Some(space_snippet) = snippet_opt(cx, space_span) {
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let lint_span = lhs.span.with_lo(lhs.span.hi());
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if space_snippet.contains('\n') {
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span_note_and_lint(
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cx,
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POSSIBLE_MISSING_COMMA,
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lint_span,
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"possibly missing a comma here",
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lint_span,
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"to remove this lint, add a comma or write the expr in a single line",
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);
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}
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}
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}
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}
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}
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}
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}
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fn check_missing_else(cx: &EarlyContext<'_>, first: &ast::Expr, second: &ast::Expr) {
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if !differing_macro_contexts(first.span, second.span)
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&& !in_macro(first.span)
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&& unsugar_if(first).is_some()
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&& (is_block(second) || unsugar_if(second).is_some())
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{
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// where the else would be
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let else_span = first.span.between(second.span);
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if let Some(else_snippet) = snippet_opt(cx, else_span) {
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if !else_snippet.contains('\n') {
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let (looks_like, next_thing) = if unsugar_if(second).is_some() {
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("an `else if`", "the second `if`")
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} else {
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("an `else {..}`", "the next block")
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};
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span_note_and_lint(
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cx,
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SUSPICIOUS_ELSE_FORMATTING,
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else_span,
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&format!("this looks like {} but the `else` is missing", looks_like),
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else_span,
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&format!(
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"to remove this lint, add the missing `else` or add a new line before {}",
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next_thing,
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),
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);
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}
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}
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}
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}
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fn is_block(expr: &ast::Expr) -> bool {
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if let ast::ExprKind::Block(..) = expr.node {
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true
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} else {
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false
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}
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}
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/// Match `if` or `if let` expressions and return the `then` and `else` block.
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fn unsugar_if(expr: &ast::Expr) -> Option<(&P<ast::Block>, &Option<P<ast::Expr>>)> {
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match expr.node {
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ast::ExprKind::If(_, ref then, ref else_) | ast::ExprKind::IfLet(_, _, ref then, ref else_) => {
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Some((then, else_))
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},
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_ => None,
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}
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}
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