From 86391abc704555610af8ba33d910bdd16a877ddb Mon Sep 17 00:00:00 2001 From: est31 Date: Sun, 11 Jun 2023 06:35:29 +0200 Subject: [PATCH] Don't lint manual_let_else in cases where the question mark operator would work Also, lint question_mark for `let...else` clauses that can be simplified to use `?`. This lint isn't perfect as it doesn't support the unstable try blocks. --- clippy_lints/src/manual_let_else.rs | 48 ++++++++++++++- clippy_lints/src/question_mark.rs | 33 +++++++++- tests/ui/manual_let_else_question_mark.fixed | 56 +++++++++++++++++ tests/ui/manual_let_else_question_mark.rs | 61 +++++++++++++++++++ tests/ui/manual_let_else_question_mark.stderr | 49 +++++++++++++++ 5 files changed, 245 insertions(+), 2 deletions(-) create mode 100644 tests/ui/manual_let_else_question_mark.fixed create mode 100644 tests/ui/manual_let_else_question_mark.rs create mode 100644 tests/ui/manual_let_else_question_mark.stderr diff --git a/clippy_lints/src/manual_let_else.rs b/clippy_lints/src/manual_let_else.rs index 59e421c16220..dcfc365a3483 100644 --- a/clippy_lints/src/manual_let_else.rs +++ b/clippy_lints/src/manual_let_else.rs @@ -1,14 +1,15 @@ use clippy_utils::diagnostics::span_lint_and_then; use clippy_utils::higher::IfLetOrMatch; use clippy_utils::msrvs::{self, Msrv}; -use clippy_utils::peel_blocks; use clippy_utils::source::snippet_with_context; use clippy_utils::ty::is_type_diagnostic_item; use clippy_utils::visitors::{Descend, Visitable}; +use clippy_utils::{is_refutable, is_res_lang_ctor, peel_blocks}; use if_chain::if_chain; use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_errors::Applicability; use rustc_hir::intravisit::{walk_expr, Visitor}; +use rustc_hir::LangItem::{OptionNone, OptionSome}; use rustc_hir::{Expr, ExprKind, HirId, ItemId, Local, MatchSource, Pat, PatKind, QPath, Stmt, StmtKind, Ty}; use rustc_lint::{LateContext, LateLintPass, LintContext}; use rustc_middle::lint::in_external_macro; @@ -85,6 +86,7 @@ impl<'tcx> LateLintPass<'tcx> for ManualLetElse { if let Some(ident_map) = expr_simple_identity_map(local.pat, let_pat, if_then); if let Some(if_else) = if_else; if expr_diverges(cx, if_else); + if pat_and_expr_can_be_question_mark(cx, let_pat, if_else).is_none(); then { emit_manual_let_else(cx, stmt.span, if_let_expr, &ident_map, let_pat, if_else); } @@ -167,6 +169,50 @@ fn emit_manual_let_else( ); } +/// Returns whether the given let pattern and else body can be turned into a question mark +/// +/// For this example: +/// ```ignore +/// let FooBar { a, b } = if let Some(a) = ex { a } else { return None }; +/// ``` +/// We get as parameters: +/// ```ignore +/// pat: Some(a) +/// else_body: return None +/// ``` + +/// And for this example: +/// ```ignore +/// let Some(FooBar { a, b }) = ex else { return None }; +/// ``` +/// We get as parameters: +/// ```ignore +/// pat: Some(FooBar { a, b }) +/// else_body: return None +/// ``` + +/// We output `Some(a)` in the first instance, and `Some(FooBar { a, b })` in the second, because +/// the question mark operator is applicable here. Callers have to check whether we are in a +/// constant or not. +pub fn pat_and_expr_can_be_question_mark<'a, 'hir>( + cx: &LateContext<'_>, + pat: &'a Pat<'hir>, + else_body: &Expr<'_>, +) -> Option<&'a Pat<'hir>> { + if let PatKind::TupleStruct(pat_path, [inner_pat], _) = pat.kind && + is_res_lang_ctor(cx, cx.qpath_res(&pat_path, pat.hir_id), OptionSome) && + !is_refutable(cx, inner_pat) && + let else_body = peel_blocks(else_body) && + let ExprKind::Ret(Some(ret_val)) = else_body.kind && + let ExprKind::Path(ret_path) = ret_val.kind && + is_res_lang_ctor(cx, cx.qpath_res(&ret_path, ret_val.hir_id), OptionNone) + { + Some(inner_pat) + } else { + None + } +} + /// Replaces the locals in the pattern /// /// For this example: diff --git a/clippy_lints/src/question_mark.rs b/clippy_lints/src/question_mark.rs index e3d940ad2a44..b1eeedc26bdb 100644 --- a/clippy_lints/src/question_mark.rs +++ b/clippy_lints/src/question_mark.rs @@ -1,3 +1,4 @@ +use crate::manual_let_else::pat_and_expr_can_be_question_mark; use clippy_utils::diagnostics::span_lint_and_sugg; use clippy_utils::source::snippet_with_applicability; use clippy_utils::ty::is_type_diagnostic_item; @@ -10,7 +11,9 @@ use if_chain::if_chain; use rustc_errors::Applicability; use rustc_hir::def::Res; use rustc_hir::LangItem::{self, OptionNone, OptionSome, ResultErr, ResultOk}; -use rustc_hir::{BindingAnnotation, ByRef, Expr, ExprKind, Node, PatKind, PathSegment, QPath}; +use rustc_hir::{ + BindingAnnotation, Block, ByRef, Expr, ExprKind, Local, Node, PatKind, PathSegment, QPath, Stmt, StmtKind, +}; use rustc_lint::{LateContext, LateLintPass}; use rustc_middle::ty::Ty; use rustc_session::declare_tool_lint; @@ -78,6 +81,29 @@ enum IfBlockType<'hir> { ), } +fn check_let_some_else_return_none(cx: &LateContext<'_>, stmt: &Stmt<'_>) { + if let StmtKind::Local(Local { pat, init: Some(init_expr), els: Some(els), .. }) = stmt.kind && + let Block { stmts: &[], expr: Some(els), .. } = els && + let Some(inner_pat) = pat_and_expr_can_be_question_mark(cx, pat, els) + { + let mut applicability = Applicability::MaybeIncorrect; + let init_expr_str = snippet_with_applicability(cx, init_expr.span, "..", &mut applicability); + let receiver_str = snippet_with_applicability(cx, inner_pat.span, "..", &mut applicability); + let sugg = format!( + "let {receiver_str} = {init_expr_str}?;", + ); + span_lint_and_sugg( + cx, + QUESTION_MARK, + stmt.span, + "this `let...else` may be rewritten with the `?` operator", + "replace it with", + sugg, + applicability, + ); + } +} + fn is_early_return(smbl: Symbol, cx: &LateContext<'_>, if_block: &IfBlockType<'_>) -> bool { match *if_block { IfBlockType::IfIs(caller, caller_ty, call_sym, if_then, _) => { @@ -259,6 +285,11 @@ fn is_try_block(cx: &LateContext<'_>, bl: &rustc_hir::Block<'_>) -> bool { } impl<'tcx> LateLintPass<'tcx> for QuestionMark { + fn check_stmt(&mut self, cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'_>) { + if !in_constant(cx, stmt.hir_id) { + check_let_some_else_return_none(cx, stmt); + } + } fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { if !in_constant(cx, expr.hir_id) { self.check_is_none_or_err_and_early_return(cx, expr); diff --git a/tests/ui/manual_let_else_question_mark.fixed b/tests/ui/manual_let_else_question_mark.fixed new file mode 100644 index 000000000000..617f127b9a86 --- /dev/null +++ b/tests/ui/manual_let_else_question_mark.fixed @@ -0,0 +1,56 @@ +//@run-rustfix +#![allow(unused_braces, unused_variables, dead_code)] +#![allow( + clippy::collapsible_else_if, + clippy::unused_unit, + clippy::let_unit_value, + clippy::match_single_binding, + clippy::never_loop +)] +#![warn(clippy::manual_let_else, clippy::question_mark)] + +enum Variant { + A(usize, usize), + B(usize), + C, +} + +fn g() -> Option<(u8, u8)> { + None +} + +fn e() -> Variant { + Variant::A(0, 0) +} + +fn main() {} + +fn foo() -> Option<()> { + // Fire here, normal case + let v = g()?; + + // Don't fire here, the pattern is refutable + let Variant::A(v, w) = e() else { return None }; + + // Fire here, the pattern is irrefutable + let (v, w) = g()?; + + // Don't fire manual_let_else in this instance: question mark can be used instead. + let v = g()?; + + // Do fire manual_let_else in this instance: question mark cannot be used here due to the return + // body. + let Some(v) = g() else { + return Some(()); + }; + + // Here we could also fire the question_mark lint, but we don't (as it's a match and not an if let). + // So we still emit manual_let_else here. For the *resulting* code, we *do* emit the question_mark + // lint, so for rustfix reasons, we allow the question_mark lint here. + #[allow(clippy::question_mark)] + { + let Some(v) = g() else { return None }; + } + + Some(()) +} diff --git a/tests/ui/manual_let_else_question_mark.rs b/tests/ui/manual_let_else_question_mark.rs new file mode 100644 index 000000000000..3cf1eca86734 --- /dev/null +++ b/tests/ui/manual_let_else_question_mark.rs @@ -0,0 +1,61 @@ +//@run-rustfix +#![allow(unused_braces, unused_variables, dead_code)] +#![allow( + clippy::collapsible_else_if, + clippy::unused_unit, + clippy::let_unit_value, + clippy::match_single_binding, + clippy::never_loop +)] +#![warn(clippy::manual_let_else, clippy::question_mark)] + +enum Variant { + A(usize, usize), + B(usize), + C, +} + +fn g() -> Option<(u8, u8)> { + None +} + +fn e() -> Variant { + Variant::A(0, 0) +} + +fn main() {} + +fn foo() -> Option<()> { + // Fire here, normal case + let Some(v) = g() else { return None }; + + // Don't fire here, the pattern is refutable + let Variant::A(v, w) = e() else { return None }; + + // Fire here, the pattern is irrefutable + let Some((v, w)) = g() else { return None }; + + // Don't fire manual_let_else in this instance: question mark can be used instead. + let v = if let Some(v_some) = g() { v_some } else { return None }; + + // Do fire manual_let_else in this instance: question mark cannot be used here due to the return + // body. + let v = if let Some(v_some) = g() { + v_some + } else { + return Some(()); + }; + + // Here we could also fire the question_mark lint, but we don't (as it's a match and not an if let). + // So we still emit manual_let_else here. For the *resulting* code, we *do* emit the question_mark + // lint, so for rustfix reasons, we allow the question_mark lint here. + #[allow(clippy::question_mark)] + { + let v = match g() { + Some(v_some) => v_some, + _ => return None, + }; + } + + Some(()) +} diff --git a/tests/ui/manual_let_else_question_mark.stderr b/tests/ui/manual_let_else_question_mark.stderr new file mode 100644 index 000000000000..31052acf75cd --- /dev/null +++ b/tests/ui/manual_let_else_question_mark.stderr @@ -0,0 +1,49 @@ +error: this `let...else` may be rewritten with the `?` operator + --> $DIR/manual_let_else_question_mark.rs:30:5 + | +LL | let Some(v) = g() else { return None }; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `let v = g()?;` + | + = note: `-D clippy::question-mark` implied by `-D warnings` + +error: this `let...else` may be rewritten with the `?` operator + --> $DIR/manual_let_else_question_mark.rs:36:5 + | +LL | let Some((v, w)) = g() else { return None }; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `let (v, w) = g()?;` + +error: this block may be rewritten with the `?` operator + --> $DIR/manual_let_else_question_mark.rs:39:13 + | +LL | let v = if let Some(v_some) = g() { v_some } else { return None }; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `g()?` + +error: this could be rewritten as `let...else` + --> $DIR/manual_let_else_question_mark.rs:43:5 + | +LL | / let v = if let Some(v_some) = g() { +LL | | v_some +LL | | } else { +LL | | return Some(()); +LL | | }; + | |______^ + | + = note: `-D clippy::manual-let-else` implied by `-D warnings` +help: consider writing + | +LL ~ let Some(v) = g() else { +LL + return Some(()); +LL + }; + | + +error: this could be rewritten as `let...else` + --> $DIR/manual_let_else_question_mark.rs:54:9 + | +LL | / let v = match g() { +LL | | Some(v_some) => v_some, +LL | | _ => return None, +LL | | }; + | |__________^ help: consider writing: `let Some(v) = g() else { return None };` + +error: aborting due to 5 previous errors +