129 lines
4.1 KiB
Rust
129 lines
4.1 KiB
Rust
use clippy_config::msrvs::{self, Msrv};
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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_context;
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use clippy_utils::sugg::Sugg;
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use clippy_utils::{contains_return, higher, in_constant, is_else_clause, is_res_lang_ctor, path_res, peel_blocks};
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use rustc_errors::Applicability;
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use rustc_hir::LangItem::{OptionNone, OptionSome};
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use rustc_hir::{Expr, ExprKind};
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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_session::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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/// ```no_run
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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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/// ```no_run
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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: Msrv,
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}
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impl IfThenSomeElseNone {
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#[must_use]
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pub fn new(msrv: Msrv) -> 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 !self.msrv.meets(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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// `bool::then()` and `bool::then_some()` are not const
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if in_constant(cx, expr.hir_id) {
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return;
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}
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let ctxt = expr.span.ctxt();
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if let Some(higher::If {
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cond,
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then,
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r#else: Some(els),
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}) = 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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&& then_expr.span.ctxt() == ctxt
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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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&& !contains_return(then_block.stmts)
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{
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let mut app = Applicability::Unspecified;
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let cond_snip = Sugg::hir_with_context(cx, cond, expr.span.ctxt(), "[condition]", &mut app)
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.maybe_par()
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.to_string();
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let arg_snip = snippet_with_context(cx, then_arg.span, ctxt, "[body]", &mut app).0;
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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) && self.msrv.meets(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 =
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format!("consider using `bool::{method_name}` like: `{cond_snip}.{method_name}({method_body})`",);
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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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