133 lines
4.5 KiB
Rust
133 lines
4.5 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_then;
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use clippy_utils::macros::{is_panic, root_macro_call_first_node};
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use clippy_utils::method_chain_args;
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use clippy_utils::ty::is_type_diagnostic_item;
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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, LateLintPass};
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use rustc_middle::ty;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::{sym, Span};
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for impls of `From<..>` that contain `panic!()` or `unwrap()`
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///
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/// ### Why is this bad?
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/// `TryFrom` should be used if there's a possibility of failure.
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///
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/// ### Example
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/// ```rust
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/// struct Foo(i32);
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///
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/// impl From<String> for Foo {
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/// fn from(s: String) -> Self {
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/// Foo(s.parse().unwrap())
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/// }
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/// }
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/// ```
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///
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/// Use instead:
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/// ```rust
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/// struct Foo(i32);
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///
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/// impl TryFrom<String> for Foo {
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/// type Error = ();
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/// fn try_from(s: String) -> Result<Self, Self::Error> {
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/// if let Ok(parsed) = s.parse() {
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/// Ok(Foo(parsed))
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/// } else {
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/// Err(())
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/// }
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/// }
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/// }
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub FALLIBLE_IMPL_FROM,
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nursery,
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"Warn on impls of `From<..>` that contain `panic!()` or `unwrap()`"
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}
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declare_lint_pass!(FallibleImplFrom => [FALLIBLE_IMPL_FROM]);
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impl<'tcx> LateLintPass<'tcx> for FallibleImplFrom {
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fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
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// check for `impl From<???> for ..`
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if_chain! {
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if let hir::ItemKind::Impl(impl_) = &item.kind;
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if let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(item.owner_id);
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if cx.tcx.is_diagnostic_item(sym::From, impl_trait_ref.skip_binder().def_id);
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then {
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lint_impl_body(cx, item.span, impl_.items);
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}
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}
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}
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}
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fn lint_impl_body(cx: &LateContext<'_>, impl_span: Span, impl_items: &[hir::ImplItemRef]) {
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use rustc_hir::intravisit::{self, Visitor};
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use rustc_hir::{Expr, ImplItemKind};
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struct FindPanicUnwrap<'a, 'tcx> {
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lcx: &'a LateContext<'tcx>,
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typeck_results: &'tcx ty::TypeckResults<'tcx>,
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result: Vec<Span>,
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}
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impl<'a, 'tcx> Visitor<'tcx> for FindPanicUnwrap<'a, 'tcx> {
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fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
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if let Some(macro_call) = root_macro_call_first_node(self.lcx, expr) {
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if is_panic(self.lcx, macro_call.def_id) {
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self.result.push(expr.span);
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}
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}
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// check for `unwrap`
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if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
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let receiver_ty = self.typeck_results.expr_ty(arglists[0].0).peel_refs();
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if is_type_diagnostic_item(self.lcx, receiver_ty, sym::Option)
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|| is_type_diagnostic_item(self.lcx, receiver_ty, sym::Result)
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{
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self.result.push(expr.span);
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}
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}
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// and check sub-expressions
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intravisit::walk_expr(self, expr);
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}
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}
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for impl_item in impl_items {
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if_chain! {
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if impl_item.ident.name == sym::from;
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if let ImplItemKind::Fn(_, body_id) =
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cx.tcx.hir().impl_item(impl_item.id).kind;
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then {
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// check the body for `begin_panic` or `unwrap`
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let body = cx.tcx.hir().body(body_id);
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let mut fpu = FindPanicUnwrap {
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lcx: cx,
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typeck_results: cx.tcx.typeck(impl_item.id.owner_id.def_id),
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result: Vec::new(),
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};
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fpu.visit_expr(body.value);
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// if we've found one, lint
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if !fpu.result.is_empty() {
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span_lint_and_then(
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cx,
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FALLIBLE_IMPL_FROM,
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impl_span,
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"consider implementing `TryFrom` instead",
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move |diag| {
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diag.help(
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"`From` is intended for infallible conversions only. \
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Use `TryFrom` if there's a possibility for the conversion to fail");
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diag.span_note(fpu.result, "potential failure(s)");
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});
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}
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}
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}
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}
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}
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