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|
use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg};
use clippy_utils::get_parent_expr;
use clippy_utils::higher;
use clippy_utils::source::snippet_block_with_applicability;
use clippy_utils::ty::implements_trait;
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::intravisit::{walk_expr, Visitor};
use rustc_hir::{BlockCheckMode, Closure, Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::lint::in_external_macro;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::sym;
declare_clippy_lint! {
/// ### What it does
/// Checks for `if` conditions that use blocks containing an
/// expression, statements or conditions that use closures with blocks.
///
/// ### Why is this bad?
/// Style, using blocks in the condition makes it hard to read.
///
/// ### Examples
/// ```rust
/// # fn somefunc() -> bool { true };
/// if { true } { /* ... */ }
///
/// if { let x = somefunc(); x } { /* ... */ }
/// ```
///
/// Use instead:
/// ```rust
/// # fn somefunc() -> bool { true };
/// if true { /* ... */ }
///
/// let res = { let x = somefunc(); x };
/// if res { /* ... */ }
/// ```
#[clippy::version = "1.45.0"]
pub BLOCKS_IN_IF_CONDITIONS,
style,
"useless or complex blocks that can be eliminated in conditions"
}
declare_lint_pass!(BlocksInIfConditions => [BLOCKS_IN_IF_CONDITIONS]);
struct ExVisitor<'a, 'tcx> {
found_block: Option<&'tcx Expr<'tcx>>,
cx: &'a LateContext<'tcx>,
}
impl<'a, 'tcx> Visitor<'tcx> for ExVisitor<'a, 'tcx> {
fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
if let ExprKind::Closure(&Closure { body, .. }) = expr.kind {
// do not lint if the closure is called using an iterator (see #1141)
if_chain! {
if let Some(parent) = get_parent_expr(self.cx, expr);
if let ExprKind::MethodCall(_, [self_arg, ..], _) = &parent.kind;
let caller = self.cx.typeck_results().expr_ty(self_arg);
if let Some(iter_id) = self.cx.tcx.get_diagnostic_item(sym::Iterator);
if implements_trait(self.cx, caller, iter_id, &[]);
then {
return;
}
}
let body = self.cx.tcx.hir().body(body);
let ex = &body.value;
if let ExprKind::Block(block, _) = ex.kind {
if !body.value.span.from_expansion() && !block.stmts.is_empty() {
self.found_block = Some(ex);
return;
}
}
}
walk_expr(self, expr);
}
}
const BRACED_EXPR_MESSAGE: &str = "omit braces around single expression condition";
const COMPLEX_BLOCK_MESSAGE: &str = "in an `if` condition, avoid complex blocks or closures with blocks; \
instead, move the block or closure higher and bind it with a `let`";
impl<'tcx> LateLintPass<'tcx> for BlocksInIfConditions {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if in_external_macro(cx.sess(), expr.span) {
return;
}
if let Some(higher::If { cond, .. }) = higher::If::hir(expr) {
if let ExprKind::Block(block, _) = &cond.kind {
if block.rules == BlockCheckMode::DefaultBlock {
if block.stmts.is_empty() {
if let Some(ex) = &block.expr {
// don't dig into the expression here, just suggest that they remove
// the block
if expr.span.from_expansion() || ex.span.from_expansion() {
return;
}
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
BLOCKS_IN_IF_CONDITIONS,
cond.span,
BRACED_EXPR_MESSAGE,
"try",
format!(
"{}",
snippet_block_with_applicability(
cx,
ex.span,
"..",
Some(expr.span),
&mut applicability
)
),
applicability,
);
}
} else {
let span = block.expr.as_ref().map_or_else(|| block.stmts[0].span, |e| e.span);
if span.from_expansion() || expr.span.from_expansion() {
return;
}
// move block higher
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
BLOCKS_IN_IF_CONDITIONS,
expr.span.with_hi(cond.span.hi()),
COMPLEX_BLOCK_MESSAGE,
"try",
format!(
"let res = {}; if res",
snippet_block_with_applicability(
cx,
block.span,
"..",
Some(expr.span),
&mut applicability
),
),
applicability,
);
}
}
} else {
let mut visitor = ExVisitor { found_block: None, cx };
walk_expr(&mut visitor, cond);
if let Some(block) = visitor.found_block {
span_lint(cx, BLOCKS_IN_IF_CONDITIONS, block.span, COMPLEX_BLOCK_MESSAGE);
}
}
}
}
}
|
