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use rustc::lint::*;
use rustc::hir;
use rustc::ty;
use syntax_pos::Span;
use utils::{match_def_path, method_chain_args, span_lint_and_then, walk_ptrs_ty, is_expn_of};
use utils::paths::{BEGIN_PANIC, BEGIN_PANIC_FMT, FROM_TRAIT, OPTION, RESULT};
declare_clippy_lint! {
pub FALLIBLE_IMPL_FROM,
nursery,
"Warn on impls of `From<..>` that contain `panic!()` or `unwrap()`"
}
pub struct FallibleImplFrom;
impl LintPass for FallibleImplFrom {
fn get_lints(&self) -> LintArray {
lint_array!(FALLIBLE_IMPL_FROM)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for FallibleImplFrom {
fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item) {
let impl_def_id = cx.tcx.hir.local_def_id(item.id);
if_chain! {
if let hir::ItemImpl(.., ref impl_items) = item.node;
if let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(impl_def_id);
if match_def_path(cx.tcx, impl_trait_ref.def_id, &FROM_TRAIT);
then {
lint_impl_body(cx, item.span, impl_items);
}
}
}
}
fn lint_impl_body<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, impl_span: Span, impl_items: &hir::HirVec<hir::ImplItemRef>) {
use rustc::hir::*;
use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
struct FindPanicUnwrap<'a, 'tcx: 'a> {
tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
tables: &'tcx ty::TypeckTables<'tcx>,
result: Vec<Span>,
}
impl<'a, 'tcx: 'a> Visitor<'tcx> for FindPanicUnwrap<'a, 'tcx> {
fn visit_expr(&mut self, expr: &'tcx Expr) {
if_chain! {
if let ExprCall(ref func_expr, _) = expr.node;
if let ExprPath(QPath::Resolved(_, ref path)) = func_expr.node;
if match_def_path(self.tcx, path.def.def_id(), &BEGIN_PANIC) ||
match_def_path(self.tcx, path.def.def_id(), &BEGIN_PANIC_FMT);
if is_expn_of(expr.span, "unreachable").is_none();
then {
self.result.push(expr.span);
}
}
if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
let reciever_ty = walk_ptrs_ty(self.tables.expr_ty(&arglists[0][0]));
if match_type(self.tcx, reciever_ty, &OPTION) || match_type(self.tcx, reciever_ty, &RESULT) {
self.result.push(expr.span);
}
}
intravisit::walk_expr(self, expr);
}
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::None
}
}
for impl_item in impl_items {
if_chain! {
if impl_item.name == "from";
if let ImplItemKind::Method(_, body_id) =
cx.tcx.hir.impl_item(impl_item.id).node;
then {
let body = cx.tcx.hir.body(body_id);
let impl_item_def_id = cx.tcx.hir.local_def_id(impl_item.id.node_id);
let mut fpu = FindPanicUnwrap {
tcx: cx.tcx,
tables: cx.tcx.typeck_tables_of(impl_item_def_id),
result: Vec::new(),
};
fpu.visit_expr(&body.value);
if !fpu.result.is_empty() {
span_lint_and_then(
cx,
FALLIBLE_IMPL_FROM,
impl_span,
"consider implementing `TryFrom` instead",
move |db| {
db.help(
"`From` is intended for infallible conversions only. \
Use `TryFrom` if there's a possibility for the conversion to fail.");
db.span_note(fpu.result, "potential failure(s)");
});
}
}
}
}
}
fn match_type(tcx: ty::TyCtxt, ty: ty::Ty, path: &[&str]) -> bool {
match ty.sty {
ty::TyAdt(adt, _) => match_def_path(tcx, adt.did, path),
_ => false,
}
}