97 lines
3.5 KiB
Rust
97 lines
3.5 KiB
Rust
use crate::utils::{
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indent_of, is_type_diagnostic_item, match_qpath, path_to_local_id, paths, reindent_multiline, snippet_opt,
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span_lint_and_sugg,
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};
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind, PatKind};
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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::symbol::sym;
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declare_clippy_lint! {
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/// **What it does:**
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/// Finds patterns that reimplement `Option::ok_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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/// **Examples:**
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/// ```rust
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/// let foo: Option<i32> = None;
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/// foo.map_or(Err("error"), |v| Ok(v));
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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.ok_or("error");
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/// ```
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pub MANUAL_OK_OR,
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pedantic,
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"finds patterns that can be encoded more concisely with `Option::ok_or`"
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}
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declare_lint_pass!(ManualOkOr => [MANUAL_OK_OR]);
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impl LateLintPass<'_> for ManualOkOr {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, scrutinee: &'tcx Expr<'tcx>) {
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if in_external_macro(cx.sess(), scrutinee.span) {
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return;
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}
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if_chain! {
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if let ExprKind::MethodCall(method_segment, _, args, _) = scrutinee.kind;
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if method_segment.ident.name == sym!(map_or);
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if args.len() == 3;
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let method_receiver = &args[0];
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let ty = cx.typeck_results().expr_ty(method_receiver);
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if is_type_diagnostic_item(cx, ty, sym::option_type);
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let or_expr = &args[1];
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if is_ok_wrapping(cx, &args[2]);
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if let ExprKind::Call(Expr { kind: ExprKind::Path(err_path), .. }, &[ref err_arg]) = or_expr.kind;
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if match_qpath(err_path, &paths::RESULT_ERR);
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if let Some(method_receiver_snippet) = snippet_opt(cx, method_receiver.span);
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if let Some(err_arg_snippet) = snippet_opt(cx, err_arg.span);
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if let Some(indent) = indent_of(cx, scrutinee.span);
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then {
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let reindented_err_arg_snippet =
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reindent_multiline(err_arg_snippet.into(), true, Some(indent + 4));
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span_lint_and_sugg(
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cx,
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MANUAL_OK_OR,
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scrutinee.span,
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"this pattern reimplements `Option::ok_or`",
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"replace with",
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format!(
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"{}.ok_or({})",
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method_receiver_snippet,
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reindented_err_arg_snippet
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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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}
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fn is_ok_wrapping(cx: &LateContext<'_>, map_expr: &Expr<'_>) -> bool {
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if let ExprKind::Path(ref qpath) = map_expr.kind {
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if match_qpath(qpath, &paths::RESULT_OK) {
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return true;
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}
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}
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if_chain! {
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if let ExprKind::Closure(_, _, body_id, ..) = map_expr.kind;
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let body = cx.tcx.hir().body(body_id);
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if let PatKind::Binding(_, param_id, ..) = body.params[0].pat.kind;
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if let ExprKind::Call(Expr { kind: ExprKind::Path(ok_path), .. }, &[ref ok_arg]) = body.value.kind;
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if match_qpath(ok_path, &paths::RESULT_OK);
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then { path_to_local_id(ok_arg, param_id) } else { false }
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}
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}
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