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|
use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::eager_or_lazy::switch_to_eager_eval;
use clippy_utils::source::snippet_with_macro_callsite;
use clippy_utils::{contains_return, higher, is_else_clause, is_lang_ctor, meets_msrv, msrvs, peel_blocks};
use rustc_hir::LangItem::{OptionNone, OptionSome};
use rustc_hir::{Expr, ExprKind, Stmt, StmtKind};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::lint::in_external_macro;
use rustc_semver::RustcVersion;
use rustc_session::{declare_tool_lint, impl_lint_pass};
declare_clippy_lint! {
/// ### What it does
/// Checks for if-else that could be written using either `bool::then` or `bool::then_some`.
///
/// ### Why is this bad?
/// Looks a little redundant. Using `bool::then` is more concise and incurs no loss of clarity.
/// For simple calculations and known values, use `bool::then_some`, which is eagerly evaluated
/// in comparison to `bool::then`.
///
/// ### Example
/// ```rust
/// # let v = vec![0];
/// let a = if v.is_empty() {
/// println!("true!");
/// Some(42)
/// } else {
/// None
/// };
/// ```
///
/// Could be written:
///
/// ```rust
/// # let v = vec![0];
/// let a = v.is_empty().then(|| {
/// println!("true!");
/// 42
/// });
/// ```
#[clippy::version = "1.53.0"]
pub IF_THEN_SOME_ELSE_NONE,
restriction,
"Finds if-else that could be written using either `bool::then` or `bool::then_some`"
}
pub struct IfThenSomeElseNone {
msrv: Option<RustcVersion>,
}
impl IfThenSomeElseNone {
#[must_use]
pub fn new(msrv: Option<RustcVersion>) -> Self {
Self { msrv }
}
}
impl_lint_pass!(IfThenSomeElseNone => [IF_THEN_SOME_ELSE_NONE]);
impl<'tcx> LateLintPass<'tcx> for IfThenSomeElseNone {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
if !meets_msrv(self.msrv, msrvs::BOOL_THEN) {
return;
}
if in_external_macro(cx.sess(), expr.span) {
return;
}
// We only care about the top-most `if` in the chain
if is_else_clause(cx.tcx, expr) {
return;
}
if let Some(higher::If { cond, then, r#else: Some(els) }) = higher::If::hir(expr)
&& let ExprKind::Block(then_block, _) = then.kind
&& let Some(then_expr) = then_block.expr
&& let ExprKind::Call(then_call, [then_arg]) = then_expr.kind
&& let ExprKind::Path(ref then_call_qpath) = then_call.kind
&& is_lang_ctor(cx, then_call_qpath, OptionSome)
&& let ExprKind::Path(ref qpath) = peel_blocks(els).kind
&& is_lang_ctor(cx, qpath, OptionNone)
&& !stmts_contains_early_return(then_block.stmts)
{
let cond_snip = snippet_with_macro_callsite(cx, cond.span, "[condition]");
let cond_snip = if matches!(cond.kind, ExprKind::Unary(_, _) | ExprKind::Binary(_, _, _)) {
format!("({})", cond_snip)
} else {
cond_snip.into_owned()
};
let arg_snip = snippet_with_macro_callsite(cx, then_arg.span, "");
let mut method_body = if then_block.stmts.is_empty() {
arg_snip.into_owned()
} else {
format!("{{ /* snippet */ {} }}", arg_snip)
};
let method_name = if switch_to_eager_eval(cx, expr) && meets_msrv(self.msrv, msrvs::BOOL_THEN_SOME) {
"then_some"
} else {
method_body.insert_str(0, "|| ");
"then"
};
let help = format!(
"consider using `bool::{}` like: `{}.{}({})`",
method_name, cond_snip, method_name, method_body,
);
span_lint_and_help(
cx,
IF_THEN_SOME_ELSE_NONE,
expr.span,
&format!("this could be simplified with `bool::{}`", method_name),
None,
&help,
);
}
}
extract_msrv_attr!(LateContext);
}
fn stmts_contains_early_return(stmts: &[Stmt<'_>]) -> bool {
stmts.iter().any(|stmt| {
let Stmt { kind: StmtKind::Semi(e), .. } = stmt else { return false };
contains_return(e)
})
}
|
