130 lines
4.5 KiB
Rust
130 lines
4.5 KiB
Rust
use crate::consts::constant_simple;
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use crate::utils;
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use crate::utils::sugg;
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir::{def, Arm, Expr, ExprKind, Pat, PatKind, QPath};
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use rustc_lint::LintContext;
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::lint::in_external_macro;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::sym;
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declare_clippy_lint! {
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/// **What it does:**
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/// Finds patterns that reimplement `Option::unwrap_or` or `Result::unwrap_or`.
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///
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/// **Why is this bad?**
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/// Concise code helps focusing on behavior instead of boilerplate.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// let foo: Option<i32> = None;
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/// match foo {
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/// Some(v) => v,
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/// None => 1,
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/// };
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/// ```
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///
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/// Use instead:
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/// ```rust
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/// let foo: Option<i32> = None;
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/// foo.unwrap_or(1);
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/// ```
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pub MANUAL_UNWRAP_OR,
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complexity,
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"finds patterns that can be encoded more concisely with `Option::unwrap_or` or `Result::unwrap_or`"
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}
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declare_lint_pass!(ManualUnwrapOr => [MANUAL_UNWRAP_OR]);
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impl LateLintPass<'_> for ManualUnwrapOr {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
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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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lint_manual_unwrap_or(cx, expr);
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}
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}
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#[derive(Copy, Clone)]
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enum Case {
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Option,
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Result,
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}
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impl Case {
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fn unwrap_fn_path(&self) -> &str {
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match self {
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Case::Option => "Option::unwrap_or",
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Case::Result => "Result::unwrap_or",
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}
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}
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}
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fn lint_manual_unwrap_or<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
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fn applicable_or_arm<'a>(arms: &'a [Arm<'a>]) -> Option<&'a Arm<'a>> {
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if_chain! {
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if arms.len() == 2;
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if arms.iter().all(|arm| arm.guard.is_none());
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if let Some((idx, or_arm)) = arms.iter().enumerate().find(|(_, arm)|
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match arm.pat.kind {
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PatKind::Path(ref some_qpath) =>
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utils::match_qpath(some_qpath, &utils::paths::OPTION_NONE),
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PatKind::TupleStruct(ref err_qpath, &[Pat { kind: PatKind::Wild, .. }], _) =>
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utils::match_qpath(err_qpath, &utils::paths::RESULT_ERR),
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_ => false,
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}
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);
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let unwrap_arm = &arms[1 - idx];
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if let PatKind::TupleStruct(ref unwrap_qpath, &[unwrap_pat], _) = unwrap_arm.pat.kind;
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if utils::match_qpath(unwrap_qpath, &utils::paths::OPTION_SOME)
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|| utils::match_qpath(unwrap_qpath, &utils::paths::RESULT_OK);
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if let PatKind::Binding(_, binding_hir_id, ..) = unwrap_pat.kind;
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if let ExprKind::Path(QPath::Resolved(_, body_path)) = unwrap_arm.body.kind;
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if let def::Res::Local(body_path_hir_id) = body_path.res;
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if body_path_hir_id == binding_hir_id;
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if !utils::usage::contains_return_break_continue_macro(or_arm.body);
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then {
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Some(or_arm)
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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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if_chain! {
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if let ExprKind::Match(scrutinee, match_arms, _) = expr.kind;
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let ty = cx.typeck_results().expr_ty(scrutinee);
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if let Some(case) = if utils::is_type_diagnostic_item(cx, ty, sym::option_type) {
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Some(Case::Option)
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} else if utils::is_type_diagnostic_item(cx, ty, sym::result_type) {
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Some(Case::Result)
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} else {
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None
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};
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if let Some(or_arm) = applicable_or_arm(match_arms);
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if let Some(or_body_snippet) = utils::snippet_opt(cx, or_arm.body.span);
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if let Some(indent) = utils::indent_of(cx, expr.span);
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if constant_simple(cx, cx.typeck_results(), or_arm.body).is_some();
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then {
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let reindented_or_body =
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utils::reindent_multiline(or_body_snippet.into(), true, Some(indent));
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utils::span_lint_and_sugg(
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cx,
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MANUAL_UNWRAP_OR, expr.span,
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&format!("this pattern reimplements `{}`", case.unwrap_fn_path()),
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"replace with",
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format!(
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"{}.unwrap_or({})",
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sugg::Sugg::hir(cx, scrutinee, "..").maybe_par(),
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reindented_or_body,
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),
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Applicability::MachineApplicable,
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);
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}
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}
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}
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