1 use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg};
2 use clippy_utils::higher;
3 use clippy_utils::source::snippet_block_with_applicability;
4 use clippy_utils::ty::implements_trait;
5 use clippy_utils::{differing_macro_contexts, get_parent_expr};
6 use if_chain::if_chain;
7 use rustc_errors::Applicability;
8 use rustc_hir::intravisit::{walk_expr, Visitor};
9 use rustc_hir::{BlockCheckMode, Expr, ExprKind};
10 use rustc_lint::{LateContext, LateLintPass, LintContext};
11 use rustc_middle::lint::in_external_macro;
12 use rustc_session::{declare_lint_pass, declare_tool_lint};
15 declare_clippy_lint! {
17 /// Checks for `if` conditions that use blocks containing an
18 /// expression, statements or conditions that use closures with blocks.
20 /// ### Why is this bad?
21 /// Style, using blocks in the condition makes it hard to read.
26 /// if { true } { /* ... */ }
29 /// if true { /* ... */ }
35 /// # fn somefunc() -> bool { true };
37 /// if { let x = somefunc(); x } { /* ... */ }
40 /// let res = { let x = somefunc(); x };
41 /// if res { /* ... */ }
43 #[clippy::version = "1.45.0"]
44 pub BLOCKS_IN_IF_CONDITIONS,
46 "useless or complex blocks that can be eliminated in conditions"
49 declare_lint_pass!(BlocksInIfConditions => [BLOCKS_IN_IF_CONDITIONS]);
51 struct ExVisitor<'a, 'tcx> {
52 found_block: Option<&'tcx Expr<'tcx>>,
53 cx: &'a LateContext<'tcx>,
56 impl<'a, 'tcx> Visitor<'tcx> for ExVisitor<'a, 'tcx> {
57 fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
58 if let ExprKind::Closure(_, _, eid, _, _) = expr.kind {
59 // do not lint if the closure is called using an iterator (see #1141)
61 if let Some(parent) = get_parent_expr(self.cx, expr);
62 if let ExprKind::MethodCall(_, [self_arg, ..], _) = &parent.kind;
63 let caller = self.cx.typeck_results().expr_ty(self_arg);
64 if let Some(iter_id) = self.cx.tcx.get_diagnostic_item(sym::Iterator);
65 if implements_trait(self.cx, caller, iter_id, &[]);
71 let body = self.cx.tcx.hir().body(eid);
73 if let ExprKind::Block(block, _) = ex.kind {
74 if !body.value.span.from_expansion() && !block.stmts.is_empty() {
75 self.found_block = Some(ex);
80 walk_expr(self, expr);
84 const BRACED_EXPR_MESSAGE: &str = "omit braces around single expression condition";
85 const COMPLEX_BLOCK_MESSAGE: &str = "in an `if` condition, avoid complex blocks or closures with blocks; \
86 instead, move the block or closure higher and bind it with a `let`";
88 impl<'tcx> LateLintPass<'tcx> for BlocksInIfConditions {
89 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
90 if in_external_macro(cx.sess(), expr.span) {
93 if let Some(higher::If { cond, .. }) = higher::If::hir(expr) {
94 if let ExprKind::Block(block, _) = &cond.kind {
95 if block.rules == BlockCheckMode::DefaultBlock {
96 if block.stmts.is_empty() {
97 if let Some(ex) = &block.expr {
98 // don't dig into the expression here, just suggest that they remove
100 if expr.span.from_expansion() || differing_macro_contexts(expr.span, ex.span) {
103 let mut applicability = Applicability::MachineApplicable;
106 BLOCKS_IN_IF_CONDITIONS,
112 snippet_block_with_applicability(
124 let span = block.expr.as_ref().map_or_else(|| block.stmts[0].span, |e| e.span);
125 if span.from_expansion() || differing_macro_contexts(expr.span, span) {
129 let mut applicability = Applicability::MachineApplicable;
132 BLOCKS_IN_IF_CONDITIONS,
133 expr.span.with_hi(cond.span.hi()),
134 COMPLEX_BLOCK_MESSAGE,
137 "let res = {}; if res",
138 snippet_block_with_applicability(
151 let mut visitor = ExVisitor { found_block: None, cx };
152 walk_expr(&mut visitor, cond);
153 if let Some(block) = visitor.found_block {
154 span_lint(cx, BLOCKS_IN_IF_CONDITIONS, block.span, COMPLEX_BLOCK_MESSAGE);