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