132 lines
4.7 KiB
Rust
132 lines
4.7 KiB
Rust
use rustc::lint::*;
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use rustc::hir;
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use rustc::ty;
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use syntax_pos::Span;
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use utils::{match_def_path, method_chain_args, span_lint_and_then, walk_ptrs_ty, is_expn_of};
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use utils::paths::{BEGIN_PANIC, BEGIN_PANIC_FMT, FROM_TRAIT, OPTION, RESULT};
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/// **What it does:** Checks for impls of `From<..>` that contain `panic!()` or `unwrap()`
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///
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/// **Why is this bad?** `TryFrom` should be used if there's a possibility of failure.
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///
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/// **Known problems:** None.
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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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/// 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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declare_lint! {
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pub FALLIBLE_IMPL_FROM, Allow,
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"Warn on impls of `From<..>` that contain `panic!()` or `unwrap()`"
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}
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pub struct FallibleImplFrom;
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impl LintPass for FallibleImplFrom {
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fn get_lints(&self) -> LintArray {
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lint_array!(FALLIBLE_IMPL_FROM)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for FallibleImplFrom {
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fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item) {
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// check for `impl From<???> for ..`
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let impl_def_id = cx.tcx.hir.local_def_id(item.id);
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if_chain! {
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if let hir::ItemImpl(.., ref impl_items) = item.node;
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if let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(impl_def_id);
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if match_def_path(cx.tcx, impl_trait_ref.def_id, &FROM_TRAIT);
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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<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, impl_span: Span, impl_items: &hir::HirVec<hir::ImplItemRef>) {
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use rustc::hir::*;
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use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
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struct FindPanicUnwrap<'a, 'tcx: 'a> {
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tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
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tables: &'tcx ty::TypeckTables<'tcx>,
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result: Vec<Span>,
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}
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impl<'a, 'tcx: 'a> Visitor<'tcx> for FindPanicUnwrap<'a, 'tcx> {
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fn visit_expr(&mut self, expr: &'tcx Expr) {
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// check for `begin_panic`
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if_chain! {
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if let ExprCall(ref func_expr, _) = expr.node;
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if let ExprPath(QPath::Resolved(_, ref path)) = func_expr.node;
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if match_def_path(self.tcx, path.def.def_id(), &BEGIN_PANIC) ||
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match_def_path(self.tcx, path.def.def_id(), &BEGIN_PANIC_FMT);
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if is_expn_of(expr.span, "unreachable").is_none();
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then {
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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 reciever_ty = walk_ptrs_ty(self.tables.expr_ty(&arglists[0][0]));
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if match_type(self.tcx, reciever_ty, &OPTION) || match_type(self.tcx, reciever_ty, &RESULT) {
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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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fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
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NestedVisitorMap::None
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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.name == "from";
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if let ImplItemKind::Method(_, body_id) =
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cx.tcx.hir.impl_item(impl_item.id).node;
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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 impl_item_def_id = cx.tcx.hir.local_def_id(impl_item.id.node_id);
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let mut fpu = FindPanicUnwrap {
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tcx: cx.tcx,
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tables: cx.tcx.typeck_tables_of(impl_item_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 |db| {
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db.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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db.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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fn match_type(tcx: ty::TyCtxt, ty: ty::Ty, path: &[&str]) -> bool {
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match ty.sty {
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ty::TyAdt(adt, _) => match_def_path(tcx, adt.did, path),
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_ => false,
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}
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}
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