| use crate::utils::{ |
| differing_macro_contexts, higher::if_block, is_type_diagnostic_item, span_lint_and_then, |
| usage::is_potentially_mutated, |
| }; |
| use if_chain::if_chain; |
| use rustc_hir::intravisit::{walk_expr, walk_fn, FnKind, NestedVisitorMap, Visitor}; |
| use rustc_hir::{BinOpKind, Body, Expr, ExprKind, FnDecl, HirId, Path, QPath, UnOp}; |
| use rustc_lint::{LateContext, LateLintPass}; |
| use rustc_middle::hir::map::Map; |
| use rustc_middle::lint::in_external_macro; |
| use rustc_middle::ty::Ty; |
| use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| use rustc_span::source_map::Span; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for calls of `unwrap[_err]()` that cannot fail. |
| /// |
| /// **Why is this bad?** Using `if let` or `match` is more idiomatic. |
| /// |
| /// **Known problems:** None |
| /// |
| /// **Example:** |
| /// ```rust |
| /// # let option = Some(0); |
| /// # fn do_something_with(_x: usize) {} |
| /// if option.is_some() { |
| /// do_something_with(option.unwrap()) |
| /// } |
| /// ``` |
| /// |
| /// Could be written: |
| /// |
| /// ```rust |
| /// # let option = Some(0); |
| /// # fn do_something_with(_x: usize) {} |
| /// if let Some(value) = option { |
| /// do_something_with(value) |
| /// } |
| /// ``` |
| pub UNNECESSARY_UNWRAP, |
| complexity, |
| "checks for calls of `unwrap[_err]()` that cannot fail" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for calls of `unwrap[_err]()` that will always fail. |
| /// |
| /// **Why is this bad?** If panicking is desired, an explicit `panic!()` should be used. |
| /// |
| /// **Known problems:** This lint only checks `if` conditions not assignments. |
| /// So something like `let x: Option<()> = None; x.unwrap();` will not be recognized. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// # let option = Some(0); |
| /// # fn do_something_with(_x: usize) {} |
| /// if option.is_none() { |
| /// do_something_with(option.unwrap()) |
| /// } |
| /// ``` |
| /// |
| /// This code will always panic. The if condition should probably be inverted. |
| pub PANICKING_UNWRAP, |
| correctness, |
| "checks for calls of `unwrap[_err]()` that will always fail" |
| } |
| |
| /// Visitor that keeps track of which variables are unwrappable. |
| struct UnwrappableVariablesVisitor<'a, 'tcx> { |
| unwrappables: Vec<UnwrapInfo<'tcx>>, |
| cx: &'a LateContext<'tcx>, |
| } |
| /// Contains information about whether a variable can be unwrapped. |
| #[derive(Copy, Clone, Debug)] |
| struct UnwrapInfo<'tcx> { |
| /// The variable that is checked |
| ident: &'tcx Path<'tcx>, |
| /// The check, like `x.is_ok()` |
| check: &'tcx Expr<'tcx>, |
| /// The branch where the check takes place, like `if x.is_ok() { .. }` |
| branch: &'tcx Expr<'tcx>, |
| /// Whether `is_some()` or `is_ok()` was called (as opposed to `is_err()` or `is_none()`). |
| safe_to_unwrap: bool, |
| } |
| |
| /// Collects the information about unwrappable variables from an if condition |
| /// The `invert` argument tells us whether the condition is negated. |
| fn collect_unwrap_info<'tcx>( |
| cx: &LateContext<'tcx>, |
| expr: &'tcx Expr<'_>, |
| branch: &'tcx Expr<'_>, |
| invert: bool, |
| ) -> Vec<UnwrapInfo<'tcx>> { |
| fn is_relevant_option_call(cx: &LateContext<'_>, ty: Ty<'_>, method_name: &str) -> bool { |
| is_type_diagnostic_item(cx, ty, sym!(option_type)) && ["is_some", "is_none"].contains(&method_name) |
| } |
| |
| fn is_relevant_result_call(cx: &LateContext<'_>, ty: Ty<'_>, method_name: &str) -> bool { |
| is_type_diagnostic_item(cx, ty, sym!(result_type)) && ["is_ok", "is_err"].contains(&method_name) |
| } |
| |
| if let ExprKind::Binary(op, left, right) = &expr.kind { |
| match (invert, op.node) { |
| (false, BinOpKind::And | BinOpKind::BitAnd) | (true, BinOpKind::Or | BinOpKind::BitOr) => { |
| let mut unwrap_info = collect_unwrap_info(cx, left, branch, invert); |
| unwrap_info.append(&mut collect_unwrap_info(cx, right, branch, invert)); |
| return unwrap_info; |
| }, |
| _ => (), |
| } |
| } else if let ExprKind::Unary(UnOp::UnNot, expr) = &expr.kind { |
| return collect_unwrap_info(cx, expr, branch, !invert); |
| } else { |
| if_chain! { |
| if let ExprKind::MethodCall(method_name, _, args, _) = &expr.kind; |
| if let ExprKind::Path(QPath::Resolved(None, path)) = &args[0].kind; |
| let ty = cx.tables().expr_ty(&args[0]); |
| let name = method_name.ident.as_str(); |
| if is_relevant_option_call(cx, ty, &name) || is_relevant_result_call(cx, ty, &name); |
| then { |
| assert!(args.len() == 1); |
| let unwrappable = match name.as_ref() { |
| "is_some" | "is_ok" => true, |
| "is_err" | "is_none" => false, |
| _ => unreachable!(), |
| }; |
| let safe_to_unwrap = unwrappable != invert; |
| return vec![UnwrapInfo { ident: path, check: expr, branch, safe_to_unwrap }]; |
| } |
| } |
| } |
| Vec::new() |
| } |
| |
| impl<'a, 'tcx> UnwrappableVariablesVisitor<'a, 'tcx> { |
| fn visit_branch(&mut self, cond: &'tcx Expr<'_>, branch: &'tcx Expr<'_>, else_branch: bool) { |
| let prev_len = self.unwrappables.len(); |
| for unwrap_info in collect_unwrap_info(self.cx, cond, branch, else_branch) { |
| if is_potentially_mutated(unwrap_info.ident, cond, self.cx) |
| || is_potentially_mutated(unwrap_info.ident, branch, self.cx) |
| { |
| // if the variable is mutated, we don't know whether it can be unwrapped: |
| continue; |
| } |
| self.unwrappables.push(unwrap_info); |
| } |
| walk_expr(self, branch); |
| self.unwrappables.truncate(prev_len); |
| } |
| } |
| |
| impl<'a, 'tcx> Visitor<'tcx> for UnwrappableVariablesVisitor<'a, 'tcx> { |
| type Map = Map<'tcx>; |
| |
| fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { |
| // Shouldn't lint when `expr` is in macro. |
| if in_external_macro(self.cx.tcx.sess, expr.span) { |
| return; |
| } |
| if let Some((cond, then, els)) = if_block(&expr) { |
| walk_expr(self, cond); |
| self.visit_branch(cond, then, false); |
| if let Some(els) = els { |
| self.visit_branch(cond, els, true); |
| } |
| } else { |
| // find `unwrap[_err]()` calls: |
| if_chain! { |
| if let ExprKind::MethodCall(ref method_name, _, ref args, _) = expr.kind; |
| if let ExprKind::Path(QPath::Resolved(None, ref path)) = args[0].kind; |
| if [sym!(unwrap), sym!(unwrap_err)].contains(&method_name.ident.name); |
| let call_to_unwrap = method_name.ident.name == sym!(unwrap); |
| if let Some(unwrappable) = self.unwrappables.iter() |
| .find(|u| u.ident.res == path.res); |
| // Span contexts should not differ with the conditional branch |
| if !differing_macro_contexts(unwrappable.branch.span, expr.span); |
| if !differing_macro_contexts(unwrappable.branch.span, unwrappable.check.span); |
| then { |
| if call_to_unwrap == unwrappable.safe_to_unwrap { |
| span_lint_and_then( |
| self.cx, |
| UNNECESSARY_UNWRAP, |
| expr.span, |
| &format!("You checked before that `{}()` cannot fail. \ |
| Instead of checking and unwrapping, it's better to use `if let` or `match`.", |
| method_name.ident.name), |
| |diag| { diag.span_label(unwrappable.check.span, "the check is happening here"); }, |
| ); |
| } else { |
| span_lint_and_then( |
| self.cx, |
| PANICKING_UNWRAP, |
| expr.span, |
| &format!("This call to `{}()` will always panic.", |
| method_name.ident.name), |
| |diag| { diag.span_label(unwrappable.check.span, "because of this check"); }, |
| ); |
| } |
| } |
| } |
| walk_expr(self, expr); |
| } |
| } |
| |
| fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { |
| NestedVisitorMap::OnlyBodies(self.cx.tcx.hir()) |
| } |
| } |
| |
| declare_lint_pass!(Unwrap => [PANICKING_UNWRAP, UNNECESSARY_UNWRAP]); |
| |
| impl<'tcx> LateLintPass<'tcx> for Unwrap { |
| fn check_fn( |
| &mut self, |
| cx: &LateContext<'tcx>, |
| kind: FnKind<'tcx>, |
| decl: &'tcx FnDecl<'_>, |
| body: &'tcx Body<'_>, |
| span: Span, |
| fn_id: HirId, |
| ) { |
| if span.from_expansion() { |
| return; |
| } |
| |
| let mut v = UnwrappableVariablesVisitor { |
| cx, |
| unwrappables: Vec::new(), |
| }; |
| |
| walk_fn(&mut v, kind, decl, body.id(), span, fn_id); |
| } |
| } |