| use if_chain::if_chain; |
| use rustc::hir::def::Def; |
| use rustc::hir::*; |
| use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; |
| use rustc::{declare_tool_lint, lint_array}; |
| use rustc_errors::Applicability; |
| use syntax::ptr::P; |
| |
| use crate::utils::paths::*; |
| use crate::utils::sugg::Sugg; |
| use crate::utils::{match_def_path, match_type, span_lint_and_then, 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" |
| } |
| |
| #[derive(Copy, Clone)] |
| pub struct Pass; |
| |
| impl LintPass for Pass { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(QUESTION_MARK) |
| } |
| |
| fn name(&self) -> &'static str { |
| "QuestionMark" |
| } |
| } |
| |
| impl Pass { |
| /// 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 ExprKind::If(if_expr, body, else_) = &expr.node; |
| if let ExprKind::MethodCall(segment, _, args) = &if_expr.node; |
| if segment.ident.name == "is_none"; |
| if Self::expression_returns_none(cx, body); |
| if let Some(subject) = args.get(0); |
| if Self::is_option(cx, subject); |
| |
| then { |
| let receiver_str = &Sugg::hir(cx, subject, ".."); |
| let mut replacement: Option<String> = None; |
| if let Some(else_) = else_ { |
| if_chain! { |
| if let ExprKind::Block(block, None) = &else_.node; |
| if block.stmts.len() == 0; |
| 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) { |
| replacement = Some(format!("{}.as_ref()?;", receiver_str)); |
| } else { |
| replacement = Some(format!("{}?;", receiver_str)); |
| } |
| |
| if let Some(replacement_str) = replacement { |
| span_lint_and_then( |
| cx, |
| QUESTION_MARK, |
| expr.span, |
| "this block may be rewritten with the `?` operator", |
| |db| { |
| db.span_suggestion( |
| expr.span, |
| "replace_it_with", |
| replacement_str, |
| Applicability::MaybeIncorrect, // snippet |
| ); |
| } |
| ) |
| } |
| } |
| } |
| } |
| |
| 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, cx.param_env, expression.span) |
| } |
| |
| fn is_option(cx: &LateContext<'_, '_>, expression: &Expr) -> bool { |
| let expr_ty = cx.tables.expr_ty(expression); |
| |
| match_type(cx, expr_ty, &OPTION) |
| } |
| |
| fn expression_returns_none(cx: &LateContext<'_, '_>, expression: &Expr) -> bool { |
| match expression.node { |
| 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 Def::Ctor(def_id, def::CtorOf::Variant, _) = cx.tables.qpath_def(qp, expression.hir_id) { |
| return match_def_path(cx.tcx, def_id, &OPTION_NONE); |
| } |
| |
| false |
| }, |
| _ => false, |
| } |
| } |
| |
| fn return_expression(block: &Block) -> Option<P<Expr>> { |
| // 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.node; |
| if let ExprKind::Ret(ref ret_expr) = expr.node; |
| if let &Some(ref ret_expr) = ret_expr; |
| |
| then { |
| return Some(ret_expr.clone()); |
| } |
| } |
| |
| // Check for `return` without a semicolon. |
| if_chain! { |
| if block.stmts.len() == 0; |
| if let Some(ExprKind::Ret(Some(ret_expr))) = block.expr.as_ref().map(|e| &e.node); |
| then { |
| return Some(ret_expr.clone()); |
| } |
| } |
| |
| None |
| } |
| } |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass { |
| fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) { |
| Self::check_is_none_and_early_return_none(cx, expr); |
| } |
| } |