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| 1 | +use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg}; |
| 2 | +use clippy_utils::source::snippet_block_with_applicability; |
| 3 | +use clippy_utils::ty::implements_trait; |
| 4 | +use clippy_utils::visitors::{for_each_expr, Descend}; |
| 5 | +use clippy_utils::{get_parent_expr, higher}; |
| 6 | +use core::ops::ControlFlow; |
| 7 | +use rustc_errors::Applicability; |
| 8 | +use rustc_hir::{BlockCheckMode, Expr, ExprKind, MatchSource}; |
| 9 | +use rustc_lint::{LateContext, LateLintPass, LintContext}; |
| 10 | +use rustc_middle::lint::in_external_macro; |
| 11 | +use rustc_session::declare_lint_pass; |
| 12 | +use rustc_span::sym; |
| 13 | + |
| 14 | +declare_clippy_lint! { |
| 15 | + /// ### What it does |
| 16 | + /// Checks for `if` conditions that use blocks containing an |
| 17 | + /// expression, statements or conditions that use closures with blocks. |
| 18 | + /// |
| 19 | + /// ### Why is this bad? |
| 20 | + /// Style, using blocks in the condition makes it hard to read. |
| 21 | + /// |
| 22 | + /// ### Examples |
| 23 | + /// ```no_run |
| 24 | + /// # fn somefunc() -> bool { true }; |
| 25 | + /// if { true } { /* ... */ } |
| 26 | + /// |
| 27 | + /// if { let x = somefunc(); x } { /* ... */ } |
| 28 | + /// ``` |
| 29 | + /// |
| 30 | + /// Use instead: |
| 31 | + /// ```no_run |
| 32 | + /// # fn somefunc() -> bool { true }; |
| 33 | + /// if true { /* ... */ } |
| 34 | + /// |
| 35 | + /// let res = { let x = somefunc(); x }; |
| 36 | + /// if res { /* ... */ } |
| 37 | + /// ``` |
| 38 | + #[clippy::version = "1.45.0"] |
| 39 | + pub BLOCKS_IN_CONDITIONS, |
| 40 | + style, |
| 41 | + "useless or complex blocks that can be eliminated in conditions" |
| 42 | +} |
| 43 | + |
| 44 | +declare_lint_pass!(BlocksInConditions => [BLOCKS_IN_CONDITIONS]); |
| 45 | + |
| 46 | +const BRACED_EXPR_MESSAGE: &str = "omit braces around single expression condition"; |
| 47 | + |
| 48 | +impl<'tcx> LateLintPass<'tcx> for BlocksInConditions { |
| 49 | + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { |
| 50 | + if in_external_macro(cx.sess(), expr.span) { |
| 51 | + return; |
| 52 | + } |
| 53 | + |
| 54 | + let Some((cond, keyword, desc)) = higher::If::hir(expr) |
| 55 | + .map(|hif| (hif.cond, "if", "an `if` condition")) |
| 56 | + .or(if let ExprKind::Match(match_ex, _, MatchSource::Normal) = expr.kind { |
| 57 | + Some((match_ex, "match", "a `match` scrutinee")) |
| 58 | + } else { |
| 59 | + None |
| 60 | + }) |
| 61 | + else { |
| 62 | + return; |
| 63 | + }; |
| 64 | + let complex_block_message = &format!( |
| 65 | + "in {desc}, avoid complex blocks or closures with blocks; \ |
| 66 | + instead, move the block or closure higher and bind it with a `let`", |
| 67 | + ); |
| 68 | + |
| 69 | + if let ExprKind::Block(block, _) = &cond.kind { |
| 70 | + if block.rules == BlockCheckMode::DefaultBlock { |
| 71 | + if block.stmts.is_empty() { |
| 72 | + if let Some(ex) = &block.expr { |
| 73 | + // don't dig into the expression here, just suggest that they remove |
| 74 | + // the block |
| 75 | + if expr.span.from_expansion() || ex.span.from_expansion() { |
| 76 | + return; |
| 77 | + } |
| 78 | + let mut applicability = Applicability::MachineApplicable; |
| 79 | + span_lint_and_sugg( |
| 80 | + cx, |
| 81 | + BLOCKS_IN_CONDITIONS, |
| 82 | + cond.span, |
| 83 | + BRACED_EXPR_MESSAGE, |
| 84 | + "try", |
| 85 | + snippet_block_with_applicability(cx, ex.span, "..", Some(expr.span), &mut applicability) |
| 86 | + .to_string(), |
| 87 | + applicability, |
| 88 | + ); |
| 89 | + } |
| 90 | + } else { |
| 91 | + let span = block.expr.as_ref().map_or_else(|| block.stmts[0].span, |e| e.span); |
| 92 | + if span.from_expansion() || expr.span.from_expansion() { |
| 93 | + return; |
| 94 | + } |
| 95 | + // move block higher |
| 96 | + let mut applicability = Applicability::MachineApplicable; |
| 97 | + span_lint_and_sugg( |
| 98 | + cx, |
| 99 | + BLOCKS_IN_CONDITIONS, |
| 100 | + expr.span.with_hi(cond.span.hi()), |
| 101 | + complex_block_message, |
| 102 | + "try", |
| 103 | + format!( |
| 104 | + "let res = {}; {keyword} res", |
| 105 | + snippet_block_with_applicability(cx, block.span, "..", Some(expr.span), &mut applicability), |
| 106 | + ), |
| 107 | + applicability, |
| 108 | + ); |
| 109 | + } |
| 110 | + } |
| 111 | + } else { |
| 112 | + let _: Option<!> = for_each_expr(cond, |e| { |
| 113 | + if let ExprKind::Closure(closure) = e.kind { |
| 114 | + // do not lint if the closure is called using an iterator (see #1141) |
| 115 | + if let Some(parent) = get_parent_expr(cx, e) |
| 116 | + && let ExprKind::MethodCall(_, self_arg, _, _) = &parent.kind |
| 117 | + && let caller = cx.typeck_results().expr_ty(self_arg) |
| 118 | + && let Some(iter_id) = cx.tcx.get_diagnostic_item(sym::Iterator) |
| 119 | + && implements_trait(cx, caller, iter_id, &[]) |
| 120 | + { |
| 121 | + return ControlFlow::Continue(Descend::No); |
| 122 | + } |
| 123 | + |
| 124 | + let body = cx.tcx.hir().body(closure.body); |
| 125 | + let ex = &body.value; |
| 126 | + if let ExprKind::Block(block, _) = ex.kind { |
| 127 | + if !body.value.span.from_expansion() && !block.stmts.is_empty() { |
| 128 | + span_lint(cx, BLOCKS_IN_CONDITIONS, ex.span, complex_block_message); |
| 129 | + return ControlFlow::Continue(Descend::No); |
| 130 | + } |
| 131 | + } |
| 132 | + } |
| 133 | + ControlFlow::Continue(Descend::Yes) |
| 134 | + }); |
| 135 | + } |
| 136 | + } |
| 137 | +} |
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