137 lines
4.7 KiB
Rust
137 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::{method_chain_args, match_def_path, span_lint_and_then, walk_ptrs_ty};
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use utils::paths::{BEGIN_PANIC, BEGIN_PANIC_FMT, FROM_TRAIT, OPTION, RESULT, STRING};
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/// **What it does:** Checks for impls of `From<&str>` and `From<String>` that contain `panic!()` or
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/// `unwrap()`
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///
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/// **Why is this bad?** `FromStr` 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 IMPL_FROM_STR, Warn,
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"Warn on impls of `From<&str>` and `From<String>` that contain `panic!()` or `unwrap()`"
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}
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pub struct ImplFromStr;
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impl LintPass for ImplFromStr {
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fn get_lints(&self) -> LintArray {
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lint_array!(IMPL_FROM_STR)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplFromStr {
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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_let_chain!{[
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let hir::ItemImpl(.., ref impl_items) = item.node,
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let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(impl_def_id),
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match_def_path(cx.tcx, impl_trait_ref.def_id, &FROM_TRAIT),
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], {
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// check if the type parameter is `str` or `String`
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let from_ty_param = impl_trait_ref.substs.type_at(1);
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let base_from_ty_param =
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walk_ptrs_ty(cx.tcx.normalize_associated_type(&from_ty_param));
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if base_from_ty_param.sty == ty::TyStr ||
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match_type(cx.tcx, base_from_ty_param, &STRING)
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{
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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_let_chain!{[
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let ExprCall(ref func_expr, _) = expr.node,
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let ExprPath(QPath::Resolved(_, ref path)) = func_expr.node,
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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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], {
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self.result.push(expr.span);
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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) ||
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match_type(self.tcx, reciever_ty, &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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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_let_chain!{[
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impl_item.name == "from",
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let ImplItemKind::Method(_, body_id) =
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cx.tcx.hir.impl_item(impl_item.id).node,
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], {
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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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IMPL_FROM_STR,
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impl_span,
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"consider implementing `FromStr` instead",
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move |db| {
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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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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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