diff options
Diffstat (limited to '')
-rw-r--r-- | src/tools/clippy/clippy_lints/src/methods/err_expect.rs | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/methods/err_expect.rs b/src/tools/clippy/clippy_lints/src/methods/err_expect.rs new file mode 100644 index 000000000..570a1b873 --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/methods/err_expect.rs @@ -0,0 +1,60 @@ +use super::ERR_EXPECT; +use clippy_utils::diagnostics::span_lint_and_sugg; +use clippy_utils::ty::implements_trait; +use clippy_utils::{meets_msrv, msrvs, ty::is_type_diagnostic_item}; +use rustc_errors::Applicability; +use rustc_lint::LateContext; +use rustc_middle::ty; +use rustc_middle::ty::Ty; +use rustc_semver::RustcVersion; +use rustc_span::{sym, Span}; + +pub(super) fn check( + cx: &LateContext<'_>, + _expr: &rustc_hir::Expr<'_>, + recv: &rustc_hir::Expr<'_>, + msrv: Option<RustcVersion>, + expect_span: Span, + err_span: Span, +) { + if_chain! { + if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Result); + // Test the version to make sure the lint can be showed (expect_err has been + // introduced in rust 1.17.0 : https://github.com/rust-lang/rust/pull/38982) + if meets_msrv(msrv, msrvs::EXPECT_ERR); + + // Grabs the `Result<T, E>` type + let result_type = cx.typeck_results().expr_ty(recv); + // Tests if the T type in a `Result<T, E>` is not None + if let Some(data_type) = get_data_type(cx, result_type); + // Tests if the T type in a `Result<T, E>` implements debug + if has_debug_impl(data_type, cx); + + then { + span_lint_and_sugg( + cx, + ERR_EXPECT, + err_span.to(expect_span), + "called `.err().expect()` on a `Result` value", + "try", + "expect_err".to_string(), + Applicability::MachineApplicable + ); + } + }; +} + +/// Given a `Result<T, E>` type, return its data (`T`). +fn get_data_type<'a>(cx: &LateContext<'_>, ty: Ty<'a>) -> Option<Ty<'a>> { + match ty.kind() { + ty::Adt(_, substs) if is_type_diagnostic_item(cx, ty, sym::Result) => substs.types().next(), + _ => None, + } +} + +/// Given a type, very if the Debug trait has been impl'd +fn has_debug_impl<'tcx>(ty: Ty<'tcx>, cx: &LateContext<'tcx>) -> bool { + cx.tcx + .get_diagnostic_item(sym::Debug) + .map_or(false, |debug| implements_trait(cx, ty, debug, &[])) +} |