rust-clippy/clippy_lints/src/manual_unwrap_or.rs

128 lines
4.5 KiB
Rust

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