| use if_chain::if_chain; |
| use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; |
| use rustc::{declare_lint_pass, declare_tool_lint}; |
| |
| use crate::utils::{higher::if_block, match_type, paths, span_lint_and_then, usage::is_potentially_mutated}; |
| use rustc::hir::intravisit::*; |
| use rustc::hir::*; |
| use syntax::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<'a, '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, |
| /// The check, like `x.is_ok()` |
| check: &'tcx Expr, |
| /// 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<'a, 'tcx>( |
| cx: &'a LateContext<'a, 'tcx>, |
| expr: &'tcx Expr, |
| invert: bool, |
| ) -> Vec<UnwrapInfo<'tcx>> { |
| if let ExprKind::Binary(op, left, right) = &expr.kind { |
| match (invert, op.node) { |
| (false, BinOpKind::And) | (false, BinOpKind::BitAnd) | (true, BinOpKind::Or) | (true, BinOpKind::BitOr) => { |
| let mut unwrap_info = collect_unwrap_info(cx, left, invert); |
| unwrap_info.append(&mut collect_unwrap_info(cx, right, invert)); |
| return unwrap_info; |
| }, |
| _ => (), |
| } |
| } else if let ExprKind::Unary(UnNot, expr) = &expr.kind { |
| return collect_unwrap_info(cx, expr, !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]); |
| if match_type(cx, ty, &paths::OPTION) || match_type(cx, ty, &paths::RESULT); |
| let name = method_name.ident.as_str(); |
| if ["is_some", "is_none", "is_ok", "is_err"].contains(&&*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, 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, 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> { |
| fn visit_expr(&mut self, expr: &'tcx Expr) { |
| 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); |
| 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), |
| |db| { db.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), |
| |db| { db.span_label(unwrappable.check.span, "because of this check"); }, |
| ); |
| } |
| } |
| } |
| walk_expr(self, expr); |
| } |
| } |
| |
| fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { |
| NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir()) |
| } |
| } |
| |
| declare_lint_pass!(Unwrap => [PANICKING_UNWRAP, UNNECESSARY_UNWRAP]); |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Unwrap { |
| fn check_fn( |
| &mut self, |
| cx: &LateContext<'a, '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); |
| } |
| } |