diff options
| -rw-r--r-- | clippy_lints/src/manual_let_else.rs | 111 | ||||
| -rw-r--r-- | clippy_utils/src/lib.rs | 102 |
2 files changed, 105 insertions, 108 deletions
diff --git a/clippy_lints/src/manual_let_else.rs b/clippy_lints/src/manual_let_else.rs index 170a040d4ae..67a2a0ef8ba 100644 --- a/clippy_lints/src/manual_let_else.rs +++ b/clippy_lints/src/manual_let_else.rs @@ -5,18 +5,15 @@ use clippy_utils::diagnostics::span_lint_and_then; use clippy_utils::higher::IfLetOrMatch; 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_lint_allowed, pat_and_expr_can_be_question_mark, peel_blocks}; +use clippy_utils::{is_lint_allowed, is_never_expr, pat_and_expr_can_be_question_mark, peel_blocks}; use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_errors::Applicability; -use rustc_hir::intravisit::{walk_expr, Visitor}; -use rustc_hir::{Expr, ExprKind, HirId, ItemId, Local, MatchSource, Pat, PatKind, QPath, Stmt, StmtKind, Ty}; +use rustc_hir::{Expr, ExprKind, MatchSource, Pat, PatKind, QPath, Stmt, StmtKind}; use rustc_lint::{LateContext, LintContext}; use rustc_middle::lint::in_external_macro; use rustc_session::declare_tool_lint; use rustc_span::symbol::{sym, Symbol}; use rustc_span::Span; -use std::ops::ControlFlow; use std::slice; declare_clippy_lint! { @@ -51,7 +48,7 @@ declare_clippy_lint! { } impl<'tcx> QuestionMark { - pub(crate) fn check_manual_let_else(&mut self, cx: &LateContext<'_>, stmt: &'tcx Stmt<'tcx>) { + pub(crate) fn check_manual_let_else(&mut self, cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'tcx>) { if !self.msrv.meets(msrvs::LET_ELSE) || in_external_macro(cx.sess(), stmt.span) { return; } @@ -67,7 +64,7 @@ impl<'tcx> QuestionMark { IfLetOrMatch::IfLet(if_let_expr, let_pat, if_then, if_else) => { if let Some(ident_map) = expr_simple_identity_map(local.pat, let_pat, if_then) && let Some(if_else) = if_else - && expr_diverges(cx, if_else) + && is_never_expr(cx, if_else) && let qm_allowed = is_lint_allowed(cx, QUESTION_MARK, stmt.hir_id) && (qm_allowed || pat_and_expr_can_be_question_mark(cx, let_pat, if_else).is_none()) { @@ -94,7 +91,7 @@ impl<'tcx> QuestionMark { let diverging_arm_opt = arms .iter() .enumerate() - .find(|(_, arm)| expr_diverges(cx, arm.body) && pat_allowed_for_else(cx, arm.pat, check_types)); + .find(|(_, arm)| is_never_expr(cx, arm.body) && pat_allowed_for_else(cx, arm.pat, check_types)); let Some((idx, diverging_arm)) = diverging_arm_opt else { return; }; @@ -272,104 +269,6 @@ fn replace_in_pattern( sn_pat.into_owned() } -/// Check whether an expression is divergent. May give false negatives. -fn expr_diverges(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { - struct V<'cx, 'tcx> { - cx: &'cx LateContext<'tcx>, - res: ControlFlow<(), Descend>, - } - impl<'tcx> Visitor<'tcx> for V<'_, '_> { - fn visit_expr(&mut self, e: &'tcx Expr<'tcx>) { - fn is_never(cx: &LateContext<'_>, expr: &'_ Expr<'_>) -> bool { - if let Some(ty) = cx.typeck_results().expr_ty_opt(expr) { - return ty.is_never(); - } - false - } - - if self.res.is_break() { - return; - } - - // We can't just call is_never on expr and be done, because the type system - // sometimes coerces the ! type to something different before we can get - // our hands on it. So instead, we do a manual search. We do fall back to - // is_never in some places when there is no better alternative. - self.res = match e.kind { - ExprKind::Continue(_) | ExprKind::Break(_, _) | ExprKind::Ret(_) => ControlFlow::Break(()), - ExprKind::Call(call, _) => { - if is_never(self.cx, e) || is_never(self.cx, call) { - ControlFlow::Break(()) - } else { - ControlFlow::Continue(Descend::Yes) - } - }, - ExprKind::MethodCall(..) => { - if is_never(self.cx, e) { - ControlFlow::Break(()) - } else { - ControlFlow::Continue(Descend::Yes) - } - }, - ExprKind::If(if_expr, if_then, if_else) => { - let else_diverges = if_else.map_or(false, |ex| expr_diverges(self.cx, ex)); - let diverges = - expr_diverges(self.cx, if_expr) || (else_diverges && expr_diverges(self.cx, if_then)); - if diverges { - ControlFlow::Break(()) - } else { - ControlFlow::Continue(Descend::No) - } - }, - ExprKind::Match(match_expr, match_arms, _) => { - let diverges = expr_diverges(self.cx, match_expr) - || match_arms.iter().all(|arm| { - let guard_diverges = arm.guard.as_ref().map_or(false, |g| expr_diverges(self.cx, g.body())); - guard_diverges || expr_diverges(self.cx, arm.body) - }); - if diverges { - ControlFlow::Break(()) - } else { - ControlFlow::Continue(Descend::No) - } - }, - - // Don't continue into loops or labeled blocks, as they are breakable, - // and we'd have to start checking labels. - ExprKind::Block(_, Some(_)) | ExprKind::Loop(..) => ControlFlow::Continue(Descend::No), - - // Default: descend - _ => ControlFlow::Continue(Descend::Yes), - }; - if let ControlFlow::Continue(Descend::Yes) = self.res { - walk_expr(self, e); - } - } - - fn visit_local(&mut self, local: &'tcx Local<'_>) { - // Don't visit the else block of a let/else statement as it will not make - // the statement divergent even though the else block is divergent. - if let Some(init) = local.init { - self.visit_expr(init); - } - } - - // Avoid unnecessary `walk_*` calls. - fn visit_ty(&mut self, _: &'tcx Ty<'tcx>) {} - fn visit_pat(&mut self, _: &'tcx Pat<'tcx>) {} - fn visit_qpath(&mut self, _: &'tcx QPath<'tcx>, _: HirId, _: Span) {} - // Avoid monomorphising all `visit_*` functions. - fn visit_nested_item(&mut self, _: ItemId) {} - } - - let mut v = V { - cx, - res: ControlFlow::Continue(Descend::Yes), - }; - expr.visit(&mut v); - v.res.is_break() -} - fn pat_allowed_for_else(cx: &LateContext<'_>, pat: &'_ Pat<'_>, check_types: bool) -> bool { // Check whether the pattern contains any bindings, as the // binding might potentially be used in the body. diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs index 1181dfc0ef9..e11f7867ff0 100644 --- a/clippy_utils/src/lib.rs +++ b/clippy_utils/src/lib.rs @@ -88,7 +88,7 @@ use rustc_hir::intravisit::{walk_expr, FnKind, Visitor}; use rustc_hir::LangItem::{OptionNone, OptionSome, ResultErr, ResultOk}; use rustc_hir::{ self as hir, def, Arm, ArrayLen, BindingAnnotation, Block, BlockCheckMode, Body, Closure, Destination, Expr, - ExprField, ExprKind, FnDecl, FnRetTy, GenericArgs, HirId, Impl, ImplItem, ImplItemKind, ImplItemRef, Item, + ExprField, ExprKind, FnDecl, FnRetTy, GenericArgs, HirId, Impl, ImplItem, ImplItemKind, ImplItemRef, Item, ItemId, ItemKind, LangItem, Local, MatchSource, Mutability, Node, OwnerId, Param, Pat, PatKind, Path, PathSegment, PrimTy, QPath, Stmt, StmtKind, TraitItem, TraitItemKind, TraitItemRef, TraitRef, TyKind, UnOp, }; @@ -117,7 +117,7 @@ use crate::ty::{ adt_and_variant_of_res, can_partially_move_ty, expr_sig, is_copy, is_recursively_primitive_type, ty_is_fn_once_param, }; -use crate::visitors::for_each_expr; +use crate::visitors::{for_each_expr, Descend}; use rustc_middle::hir::nested_filter; @@ -2974,3 +2974,101 @@ pub fn pat_is_wild<'tcx>(cx: &LateContext<'tcx>, pat: &'tcx PatKind<'_>, body: i _ => false, } } + +/// Check if the expression either returns, or could be coerced into returning, `!`. +pub fn is_never_expr(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { + struct V<'cx, 'tcx> { + cx: &'cx LateContext<'tcx>, + res: ControlFlow<(), Descend>, + } + impl<'tcx> Visitor<'tcx> for V<'_, '_> { + fn visit_expr(&mut self, e: &'tcx Expr<'tcx>) { + fn is_never(cx: &LateContext<'_>, expr: &'_ Expr<'_>) -> bool { + if let Some(ty) = cx.typeck_results().expr_ty_opt(expr) { + return ty.is_never(); + } + false + } + + if self.res.is_break() { + return; + } + + // We can't just call is_never on expr and be done, because the type system + // sometimes coerces the ! type to something different before we can get + // our hands on it. So instead, we do a manual search. We do fall back to + // is_never in some places when there is no better alternative. + self.res = match e.kind { + ExprKind::Continue(_) | ExprKind::Break(_, _) | ExprKind::Ret(_) => ControlFlow::Break(()), + ExprKind::Call(call, _) => { + if is_never(self.cx, e) || is_never(self.cx, call) { + ControlFlow::Break(()) + } else { + ControlFlow::Continue(Descend::Yes) + } + }, + ExprKind::MethodCall(..) => { + if is_never(self.cx, e) { + ControlFlow::Break(()) + } else { + ControlFlow::Continue(Descend::Yes) + } + }, + ExprKind::If(if_expr, if_then, if_else) => { + let else_diverges = if_else.map_or(false, |ex| is_never_expr(self.cx, ex)); + let diverges = + is_never_expr(self.cx, if_expr) || (else_diverges && is_never_expr(self.cx, if_then)); + if diverges { + ControlFlow::Break(()) + } else { + ControlFlow::Continue(Descend::No) + } + }, + ExprKind::Match(match_expr, match_arms, _) => { + let diverges = is_never_expr(self.cx, match_expr) + || match_arms.iter().all(|arm| { + let guard_diverges = arm.guard.as_ref().map_or(false, |g| is_never_expr(self.cx, g.body())); + guard_diverges || is_never_expr(self.cx, arm.body) + }); + if diverges { + ControlFlow::Break(()) + } else { + ControlFlow::Continue(Descend::No) + } + }, + + // Don't continue into loops or labeled blocks, as they are breakable, + // and we'd have to start checking labels. + ExprKind::Block(_, Some(_)) | ExprKind::Loop(..) => ControlFlow::Continue(Descend::No), + + // Default: descend + _ => ControlFlow::Continue(Descend::Yes), + }; + if let ControlFlow::Continue(Descend::Yes) = self.res { + walk_expr(self, e); + } + } + + fn visit_local(&mut self, local: &'tcx Local<'_>) { + // Don't visit the else block of a let/else statement as it will not make + // the statement divergent even though the else block is divergent. + if let Some(init) = local.init { + self.visit_expr(init); + } + } + + // Avoid unnecessary `walk_*` calls. + fn visit_ty(&mut self, _: &'tcx hir::Ty<'tcx>) {} + fn visit_pat(&mut self, _: &'tcx Pat<'tcx>) {} + fn visit_qpath(&mut self, _: &'tcx QPath<'tcx>, _: HirId, _: Span) {} + // Avoid monomorphising all `visit_*` functions. + fn visit_nested_item(&mut self, _: ItemId) {} + } + + let mut v = V { + cx, + res: ControlFlow::Continue(Descend::Yes), + }; + expr.visit(&mut v); + v.res.is_break() +} |