76 lines
2.9 KiB
Rust
76 lines
2.9 KiB
Rust
|
use clippy_utils::{diagnostics::span_lint_and_sugg, higher::If, is_from_proc_macro, source::snippet_opt};
|
||
|
|
use rustc_errors::Applicability;
|
||
|
|
use rustc_hir::{ExprKind, Stmt, StmtKind};
|
||
|
|
use rustc_lint::{LateContext, LateLintPass, LintContext};
|
||
|
|
use rustc_middle::lint::in_external_macro;
|
||
|
|
use rustc_session::{declare_lint_pass, declare_tool_lint};
|
||
|
|
|
||
|
|
declare_clippy_lint! {
|
||
|
|
/// ### What it does
|
||
|
|
/// Checks for empty `if` branches with no else branch.
|
||
|
|
///
|
||
|
|
/// ### Why is this bad?
|
||
|
|
/// It can be entirely omitted, and often the condition too.
|
||
|
|
///
|
||
|
|
/// ### Known issues
|
||
|
|
/// This will usually only suggest to remove the `if` statement, not the condition. Other lints
|
||
|
|
/// such as `no_effect` will take care of removing the condition if it's unnecessary.
|
||
|
|
///
|
||
|
|
/// ### Example
|
||
|
|
/// ```rust,ignore
|
||
|
|
/// if really_expensive_condition(&i) {}
|
||
|
|
/// if really_expensive_condition_with_side_effects(&mut i) {}
|
||
|
|
/// ```
|
||
|
|
/// Use instead:
|
||
|
|
/// ```rust,ignore
|
||
|
|
/// // <omitted>
|
||
|
|
/// really_expensive_condition_with_side_effects(&mut i);
|
||
|
|
/// ```
|
||
|
|
#[clippy::version = "1.72.0"]
|
||
|
|
pub NEEDLESS_IF,
|
||
|
|
complexity,
|
||
|
|
"checks for empty if branches"
|
||
|
|
}
|
||
|
|
declare_lint_pass!(NeedlessIf => [NEEDLESS_IF]);
|
||
|
|
|
||
|
|
impl LateLintPass<'_> for NeedlessIf {
|
||
|
|
fn check_stmt<'tcx>(&mut self, cx: &LateContext<'tcx>, stmt: &Stmt<'tcx>) {
|
||
|
|
if let StmtKind::Expr(expr) = stmt.kind
|
||
|
|
&& let Some(If {cond, then, r#else: None }) = If::hir(expr)
|
||
|
|
&& let ExprKind::Block(block, ..) = then.kind
|
||
|
|
&& block.stmts.is_empty()
|
||
|
|
&& block.expr.is_none()
|
||
|
|
&& !in_external_macro(cx.sess(), expr.span)
|
||
|
|
&& !is_from_proc_macro(cx, expr)
|
||
|
|
&& let Some(then_snippet) = snippet_opt(cx, then.span)
|
||
|
|
// Ignore
|
||
|
|
// - empty macro expansions
|
||
|
|
// - empty reptitions in macro expansions
|
||
|
|
// - comments
|
||
|
|
// - #[cfg]'d out code
|
||
|
|
&& then_snippet.chars().all(|ch| matches!(ch, '{' | '}') || ch.is_ascii_whitespace())
|
||
|
|
&& let Some(cond_snippet) = snippet_opt(cx, cond.span)
|
||
|
|
{
|
||
|
|
span_lint_and_sugg(
|
||
|
|
cx,
|
||
|
|
NEEDLESS_IF,
|
||
|
|
stmt.span,
|
||
|
|
"this `if` branch is empty",
|
||
|
|
"you can remove it",
|
||
|
|
if cond.can_have_side_effects() || !cx.tcx.hir().attrs(stmt.hir_id).is_empty() {
|
||
|
|
// `{ foo }` or `{ foo } && bar` placed into a statement position would be
|
||
|
|
// interpreted as a block statement, force it to be an expression
|
||
|
|
if cond_snippet.starts_with('{') {
|
||
|
|
format!("({cond_snippet});")
|
||
|
|
} else {
|
||
|
|
format!("{cond_snippet};")
|
||
|
|
}
|
||
|
|
} else {
|
||
|
|
String::new()
|
||
|
|
},
|
||
|
|
Applicability::MachineApplicable,
|
||
|
|
);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|