| use clippy_utils::diagnostics::span_lint_hir_and_then; |
| use clippy_utils::ty::is_type_diagnostic_item; |
| use clippy_utils::usage::is_potentially_mutated; |
| use clippy_utils::{higher, path_to_local}; |
| use if_chain::if_chain; |
| use rustc_errors::Applicability; |
| use rustc_hir::intravisit::{walk_expr, walk_fn, FnKind, Visitor}; |
| use rustc_hir::{BinOpKind, Body, Expr, ExprKind, FnDecl, HirId, PathSegment, UnOp}; |
| use rustc_lint::{LateContext, LateLintPass}; |
| use rustc_middle::hir::nested_filter; |
| use rustc_middle::lint::in_external_macro; |
| use rustc_middle::ty::Ty; |
| use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| use rustc_span::def_id::LocalDefId; |
| use rustc_span::source_map::Span; |
| use rustc_span::sym; |
| |
| 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. |
| /// |
| /// ### 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) |
| /// } |
| /// ``` |
| #[clippy::version = "pre 1.29.0"] |
| 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. |
| #[clippy::version = "pre 1.29.0"] |
| 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>, |
| } |
| |
| /// What kind of unwrappable this is. |
| #[derive(Copy, Clone, Debug)] |
| enum UnwrappableKind { |
| Option, |
| Result, |
| } |
| |
| impl UnwrappableKind { |
| fn success_variant_pattern(self) -> &'static str { |
| match self { |
| UnwrappableKind::Option => "Some(..)", |
| UnwrappableKind::Result => "Ok(..)", |
| } |
| } |
| |
| fn error_variant_pattern(self) -> &'static str { |
| match self { |
| UnwrappableKind::Option => "None", |
| UnwrappableKind::Result => "Err(..)", |
| } |
| } |
| } |
| |
| /// Contains information about whether a variable can be unwrapped. |
| #[derive(Copy, Clone, Debug)] |
| struct UnwrapInfo<'tcx> { |
| /// The variable that is checked |
| local_id: HirId, |
| /// The if itself |
| if_expr: &'tcx Expr<'tcx>, |
| /// The check, like `x.is_ok()` |
| check: &'tcx Expr<'tcx>, |
| /// The check's name, like `is_ok` |
| check_name: &'tcx PathSegment<'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, |
| /// What kind of unwrappable this is. |
| kind: UnwrappableKind, |
| /// If the check is the entire condition (`if x.is_ok()`) or only a part of it (`foo() && |
| /// x.is_ok()`) |
| is_entire_condition: 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>, |
| if_expr: &'tcx Expr<'_>, |
| expr: &'tcx Expr<'_>, |
| branch: &'tcx Expr<'_>, |
| invert: bool, |
| is_entire_condition: 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) && ["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) && ["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, if_expr, left, branch, invert, false); |
| unwrap_info.append(&mut collect_unwrap_info(cx, if_expr, right, branch, invert, false)); |
| return unwrap_info; |
| }, |
| _ => (), |
| } |
| } else if let ExprKind::Unary(UnOp::Not, expr) = &expr.kind { |
| return collect_unwrap_info(cx, if_expr, expr, branch, !invert, false); |
| } else { |
| if_chain! { |
| if let ExprKind::MethodCall(method_name, receiver, args, _) = &expr.kind; |
| if let Some(local_id) = path_to_local(receiver); |
| let ty = cx.typeck_results().expr_ty(receiver); |
| 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.is_empty()); |
| let unwrappable = match name { |
| "is_some" | "is_ok" => true, |
| "is_err" | "is_none" => false, |
| _ => unreachable!(), |
| }; |
| let safe_to_unwrap = unwrappable != invert; |
| let kind = if is_type_diagnostic_item(cx, ty, sym::Option) { |
| UnwrappableKind::Option |
| } else { |
| UnwrappableKind::Result |
| }; |
| |
| return vec![ |
| UnwrapInfo { |
| local_id, |
| if_expr, |
| check: expr, |
| check_name: method_name, |
| branch, |
| safe_to_unwrap, |
| kind, |
| is_entire_condition, |
| } |
| ] |
| } |
| } |
| } |
| Vec::new() |
| } |
| |
| impl<'a, 'tcx> UnwrappableVariablesVisitor<'a, 'tcx> { |
| fn visit_branch( |
| &mut self, |
| if_expr: &'tcx Expr<'_>, |
| cond: &'tcx Expr<'_>, |
| branch: &'tcx Expr<'_>, |
| else_branch: bool, |
| ) { |
| let prev_len = self.unwrappables.len(); |
| for unwrap_info in collect_unwrap_info(self.cx, if_expr, cond, branch, else_branch, true) { |
| if is_potentially_mutated(unwrap_info.local_id, cond, self.cx) |
| || is_potentially_mutated(unwrap_info.local_id, 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 NestedFilter = nested_filter::OnlyBodies; |
| |
| 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(higher::If { cond, then, r#else }) = higher::If::hir(expr) { |
| walk_expr(self, cond); |
| self.visit_branch(expr, cond, then, false); |
| if let Some(else_inner) = r#else { |
| self.visit_branch(expr, cond, else_inner, true); |
| } |
| } else { |
| // find `unwrap[_err]()` calls: |
| if_chain! { |
| if let ExprKind::MethodCall(method_name, self_arg, ..) = expr.kind; |
| if let Some(id) = path_to_local(self_arg); |
| if [sym::unwrap, sym::expect, sym!(unwrap_err)].contains(&method_name.ident.name); |
| let call_to_unwrap = [sym::unwrap, sym::expect].contains(&method_name.ident.name); |
| if let Some(unwrappable) = self.unwrappables.iter() |
| .find(|u| u.local_id == id); |
| // Span contexts should not differ with the conditional branch |
| let span_ctxt = expr.span.ctxt(); |
| if unwrappable.branch.span.ctxt() == span_ctxt; |
| if unwrappable.check.span.ctxt() == span_ctxt; |
| then { |
| if call_to_unwrap == unwrappable.safe_to_unwrap { |
| let is_entire_condition = unwrappable.is_entire_condition; |
| let unwrappable_variable_name = self.cx.tcx.hir().name(unwrappable.local_id); |
| let suggested_pattern = if call_to_unwrap { |
| unwrappable.kind.success_variant_pattern() |
| } else { |
| unwrappable.kind.error_variant_pattern() |
| }; |
| |
| span_lint_hir_and_then( |
| self.cx, |
| UNNECESSARY_UNWRAP, |
| expr.hir_id, |
| expr.span, |
| &format!( |
| "called `{}` on `{unwrappable_variable_name}` after checking its variant with `{}`", |
| method_name.ident.name, |
| unwrappable.check_name.ident.as_str(), |
| ), |
| |diag| { |
| if is_entire_condition { |
| diag.span_suggestion( |
| unwrappable.check.span.with_lo(unwrappable.if_expr.span.lo()), |
| "try", |
| format!( |
| "if let {suggested_pattern} = {unwrappable_variable_name}", |
| ), |
| // We don't track how the unwrapped value is used inside the |
| // block or suggest deleting the unwrap, so we can't offer a |
| // fixable solution. |
| Applicability::Unspecified, |
| ); |
| } else { |
| diag.span_label(unwrappable.check.span, "the check is happening here"); |
| diag.help("try using `if let` or `match`"); |
| } |
| }, |
| ); |
| } else { |
| span_lint_hir_and_then( |
| self.cx, |
| PANICKING_UNWRAP, |
| expr.hir_id, |
| 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) -> Self::Map { |
| 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: LocalDefId, |
| ) { |
| if span.from_expansion() { |
| return; |
| } |
| |
| let mut v = UnwrappableVariablesVisitor { |
| cx, |
| unwrappables: Vec::new(), |
| }; |
| |
| walk_fn(&mut v, kind, decl, body.id(), fn_id); |
| } |
| } |