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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::{indent_of, reindent_multiline, snippet_opt};
use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::{is_lang_ctor, path_to_local_id};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::LangItem::{ResultErr, ResultOk};
use rustc_hir::{Closure, Expr, ExprKind, PatKind};
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};
use rustc_span::symbol::sym;
declare_clippy_lint! {
/// ### What it does
///
/// Finds patterns that reimplement `Option::ok_or`.
///
/// ### Why is this bad?
///
/// Concise code helps focusing on behavior instead of boilerplate.
///
/// ### Examples
/// ```rust
/// let foo: Option<i32> = None;
/// foo.map_or(Err("error"), |v| Ok(v));
/// ```
///
/// Use instead:
/// ```rust
/// let foo: Option<i32> = None;
/// foo.ok_or("error");
/// ```
#[clippy::version = "1.49.0"]
pub MANUAL_OK_OR,
pedantic,
"finds patterns that can be encoded more concisely with `Option::ok_or`"
}
declare_lint_pass!(ManualOkOr => [MANUAL_OK_OR]);
impl<'tcx> LateLintPass<'tcx> for ManualOkOr {
fn check_expr(&mut self, cx: &LateContext<'tcx>, scrutinee: &'tcx Expr<'tcx>) {
if in_external_macro(cx.sess(), scrutinee.span) {
return;
}
if_chain! {
if let ExprKind::MethodCall(method_segment, args, _) = scrutinee.kind;
if method_segment.ident.name == sym!(map_or);
if args.len() == 3;
let method_receiver = &args[0];
let ty = cx.typeck_results().expr_ty(method_receiver);
if is_type_diagnostic_item(cx, ty, sym::Option);
let or_expr = &args[1];
if is_ok_wrapping(cx, &args[2]);
if let ExprKind::Call(Expr { kind: ExprKind::Path(err_path), .. }, &[ref err_arg]) = or_expr.kind;
if is_lang_ctor(cx, err_path, ResultErr);
if let Some(method_receiver_snippet) = snippet_opt(cx, method_receiver.span);
if let Some(err_arg_snippet) = snippet_opt(cx, err_arg.span);
if let Some(indent) = indent_of(cx, scrutinee.span);
then {
let reindented_err_arg_snippet =
reindent_multiline(err_arg_snippet.into(), true, Some(indent + 4));
span_lint_and_sugg(
cx,
MANUAL_OK_OR,
scrutinee.span,
"this pattern reimplements `Option::ok_or`",
"replace with",
format!(
"{}.ok_or({})",
method_receiver_snippet,
reindented_err_arg_snippet
),
Applicability::MachineApplicable,
);
}
}
}
}
fn is_ok_wrapping(cx: &LateContext<'_>, map_expr: &Expr<'_>) -> bool {
if let ExprKind::Path(ref qpath) = map_expr.kind {
if is_lang_ctor(cx, qpath, ResultOk) {
return true;
}
}
if_chain! {
if let ExprKind::Closure(&Closure { body, .. }) = map_expr.kind;
let body = cx.tcx.hir().body(body);
if let PatKind::Binding(_, param_id, ..) = body.params[0].pat.kind;
if let ExprKind::Call(Expr { kind: ExprKind::Path(ok_path), .. }, &[ref ok_arg]) = body.value.kind;
if is_lang_ctor(cx, ok_path, ResultOk);
then { path_to_local_id(ok_arg, param_id) } else { false }
}
}
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