46 lines
1.6 KiB
Rust
46 lines
1.6 KiB
Rust
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use crate::utils::{implements_trait, is_type_diagnostic_item, span_lint_and_help};
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use if_chain::if_chain;
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use rustc_hir as hir;
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use rustc_lint::LateContext;
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use rustc_middle::ty::{self, Ty};
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use rustc_span::sym;
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use super::OK_EXPECT;
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/// lint use of `ok().expect()` for `Result`s
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pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, ok_args: &[hir::Expr<'_>]) {
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if_chain! {
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// lint if the caller of `ok()` is a `Result`
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if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&ok_args[0]), sym::result_type);
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let result_type = cx.typeck_results().expr_ty(&ok_args[0]);
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if let Some(error_type) = get_error_type(cx, result_type);
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if has_debug_impl(error_type, cx);
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then {
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span_lint_and_help(
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cx,
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OK_EXPECT,
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expr.span,
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"called `ok().expect()` on a `Result` value",
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None,
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"you can call `expect()` directly on the `Result`",
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);
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}
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}
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}
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/// Given a `Result<T, E>` type, return its error type (`E`).
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fn get_error_type<'a>(cx: &LateContext<'_>, ty: Ty<'a>) -> Option<Ty<'a>> {
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match ty.kind() {
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ty::Adt(_, substs) if is_type_diagnostic_item(cx, ty, sym::result_type) => substs.types().nth(1),
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_ => None,
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}
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}
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/// This checks whether a given type is known to implement Debug.
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fn has_debug_impl<'tcx>(ty: Ty<'tcx>, cx: &LateContext<'tcx>) -> bool {
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cx.tcx
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.get_diagnostic_item(sym::debug_trait)
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.map_or(false, |debug| implements_trait(cx, ty, debug, &[]))
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}
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