| use if_chain::if_chain; |
| use rustc_errors::Applicability; |
| use rustc_hir::def::{DefKind, Res}; |
| use rustc_hir::{def, BindingAnnotation, Block, Expr, ExprKind, MatchSource, PatKind, StmtKind}; |
| use rustc_lint::{LateContext, LateLintPass}; |
| use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| |
| use crate::utils::sugg::Sugg; |
| use crate::utils::{ |
| higher, is_type_diagnostic_item, match_def_path, match_qpath, paths, snippet_with_applicability, |
| span_lint_and_sugg, SpanlessEq, |
| }; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for expressions that could be replaced by the question mark operator. |
| /// |
| /// **Why is this bad?** Question mark usage is more idiomatic. |
| /// |
| /// **Known problems:** None |
| /// |
| /// **Example:** |
| /// ```ignore |
| /// if option.is_none() { |
| /// return None; |
| /// } |
| /// ``` |
| /// |
| /// Could be written: |
| /// |
| /// ```ignore |
| /// option?; |
| /// ``` |
| pub QUESTION_MARK, |
| style, |
| "checks for expressions that could be replaced by the question mark operator" |
| } |
| |
| declare_lint_pass!(QuestionMark => [QUESTION_MARK]); |
| |
| impl QuestionMark { |
| /// Checks if the given expression on the given context matches the following structure: |
| /// |
| /// ```ignore |
| /// if option.is_none() { |
| /// return None; |
| /// } |
| /// ``` |
| /// |
| /// If it matches, it will suggest to use the question mark operator instead |
| fn check_is_none_and_early_return_none(cx: &LateContext<'_>, expr: &Expr<'_>) { |
| if_chain! { |
| if let Some((if_expr, body, else_)) = higher::if_block(&expr); |
| if let ExprKind::MethodCall(segment, _, args, _) = &if_expr.kind; |
| if segment.ident.name == sym!(is_none); |
| if Self::expression_returns_none(cx, body); |
| if let Some(subject) = args.get(0); |
| if Self::is_option(cx, subject); |
| |
| then { |
| let mut applicability = Applicability::MachineApplicable; |
| let receiver_str = &Sugg::hir_with_applicability(cx, subject, "..", &mut applicability); |
| let mut replacement: Option<String> = None; |
| if let Some(else_) = else_ { |
| if_chain! { |
| if let ExprKind::Block(block, None) = &else_.kind; |
| if block.stmts.is_empty(); |
| if let Some(block_expr) = &block.expr; |
| if SpanlessEq::new(cx).ignore_fn().eq_expr(subject, block_expr); |
| then { |
| replacement = Some(format!("Some({}?)", receiver_str)); |
| } |
| } |
| } else if Self::moves_by_default(cx, subject) |
| && !matches!(subject.kind, ExprKind::Call(..) | ExprKind::MethodCall(..)) |
| { |
| replacement = Some(format!("{}.as_ref()?;", receiver_str)); |
| } else { |
| replacement = Some(format!("{}?;", receiver_str)); |
| } |
| |
| if let Some(replacement_str) = replacement { |
| span_lint_and_sugg( |
| cx, |
| QUESTION_MARK, |
| expr.span, |
| "this block may be rewritten with the `?` operator", |
| "replace it with", |
| replacement_str, |
| applicability, |
| ) |
| } |
| } |
| } |
| } |
| |
| fn check_if_let_some_and_early_return_none(cx: &LateContext<'_>, expr: &Expr<'_>) { |
| if_chain! { |
| if let ExprKind::Match(subject, arms, source) = &expr.kind; |
| if *source == MatchSource::IfLetDesugar { contains_else_clause: true }; |
| if Self::is_option(cx, subject); |
| |
| if let PatKind::TupleStruct(path1, fields, None) = &arms[0].pat.kind; |
| if match_qpath(path1, &["Some"]); |
| if let PatKind::Binding(annot, _, bind, _) = &fields[0].kind; |
| let by_ref = matches!(annot, BindingAnnotation::Ref | BindingAnnotation::RefMut); |
| |
| if let ExprKind::Block(block, None) = &arms[0].body.kind; |
| if block.stmts.is_empty(); |
| if let Some(trailing_expr) = &block.expr; |
| if let ExprKind::Path(path) = &trailing_expr.kind; |
| if match_qpath(path, &[&bind.as_str()]); |
| |
| if let PatKind::Wild = arms[1].pat.kind; |
| if Self::expression_returns_none(cx, arms[1].body); |
| then { |
| let mut applicability = Applicability::MachineApplicable; |
| let receiver_str = snippet_with_applicability(cx, subject.span, "..", &mut applicability); |
| let replacement = format!( |
| "{}{}?", |
| receiver_str, |
| if by_ref { ".as_ref()" } else { "" }, |
| ); |
| |
| span_lint_and_sugg( |
| cx, |
| QUESTION_MARK, |
| expr.span, |
| "this if-let-else may be rewritten with the `?` operator", |
| "replace it with", |
| replacement, |
| applicability, |
| ) |
| } |
| } |
| } |
| |
| fn moves_by_default(cx: &LateContext<'_>, expression: &Expr<'_>) -> bool { |
| let expr_ty = cx.tables().expr_ty(expression); |
| |
| !expr_ty.is_copy_modulo_regions(cx.tcx.at(expression.span), cx.param_env) |
| } |
| |
| fn is_option(cx: &LateContext<'_>, expression: &Expr<'_>) -> bool { |
| let expr_ty = cx.tables().expr_ty(expression); |
| |
| is_type_diagnostic_item(cx, expr_ty, sym!(option_type)) |
| } |
| |
| fn expression_returns_none(cx: &LateContext<'_>, expression: &Expr<'_>) -> bool { |
| match expression.kind { |
| ExprKind::Block(ref block, _) => { |
| if let Some(return_expression) = Self::return_expression(block) { |
| return Self::expression_returns_none(cx, &return_expression); |
| } |
| |
| false |
| }, |
| ExprKind::Ret(Some(ref expr)) => Self::expression_returns_none(cx, expr), |
| ExprKind::Path(ref qp) => { |
| if let Res::Def(DefKind::Ctor(def::CtorOf::Variant, def::CtorKind::Const), def_id) = |
| cx.qpath_res(qp, expression.hir_id) |
| { |
| return match_def_path(cx, def_id, &paths::OPTION_NONE); |
| } |
| |
| false |
| }, |
| _ => false, |
| } |
| } |
| |
| fn return_expression<'tcx>(block: &Block<'tcx>) -> Option<&'tcx Expr<'tcx>> { |
| // Check if last expression is a return statement. Then, return the expression |
| if_chain! { |
| if block.stmts.len() == 1; |
| if let Some(expr) = block.stmts.iter().last(); |
| if let StmtKind::Semi(ref expr) = expr.kind; |
| if let ExprKind::Ret(ret_expr) = expr.kind; |
| if let Some(ret_expr) = ret_expr; |
| |
| then { |
| return Some(ret_expr); |
| } |
| } |
| |
| // Check for `return` without a semicolon. |
| if_chain! { |
| if block.stmts.is_empty(); |
| if let Some(ExprKind::Ret(Some(ret_expr))) = block.expr.as_ref().map(|e| &e.kind); |
| then { |
| return Some(ret_expr); |
| } |
| } |
| |
| None |
| } |
| } |
| |
| impl<'tcx> LateLintPass<'tcx> for QuestionMark { |
| fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { |
| Self::check_is_none_and_early_return_none(cx, expr); |
| Self::check_if_let_some_and_early_return_none(cx, expr); |
| } |
| } |