Add needless_type_cast lint
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,289 @@ | ||
| use clippy_utils::diagnostics::span_lint_and_sugg; | ||
| use clippy_utils::visitors::{Descend, for_each_expr, for_each_expr_without_closures}; | ||
| use core::ops::ControlFlow; | ||
| use rustc_data_structures::fx::FxHashMap; | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir::def::{DefKind, Res}; | ||
| use rustc_hir::{BlockCheckMode, Body, Expr, ExprKind, HirId, LetStmt, PatKind, StmtKind, UnsafeSource}; | ||
| use rustc_lint::LateContext; | ||
| use rustc_middle::ty::{Ty, TypeVisitableExt}; | ||
| use rustc_span::Span; | ||
|
|
||
| use super::NEEDLESS_TYPE_CAST; | ||
|
|
||
| struct BindingInfo<'a> { | ||
| source_ty: Ty<'a>, | ||
| ty_span: Span, | ||
| } | ||
|
|
||
| struct UsageInfo<'a> { | ||
| cast_to: Option<Ty<'a>>, | ||
| in_generic_context: bool, | ||
| } | ||
|
|
||
| pub(super) fn check<'a>(cx: &LateContext<'a>, body: &Body<'a>) { | ||
| let mut bindings: FxHashMap<HirId, BindingInfo<'a>> = FxHashMap::default(); | ||
|
|
||
| for_each_expr_without_closures(body.value, |expr| { | ||
| match expr.kind { | ||
| ExprKind::Block(block, _) => { | ||
| for stmt in block.stmts { | ||
| if let StmtKind::Let(let_stmt) = stmt.kind { | ||
| collect_binding_from_local(cx, let_stmt, &mut bindings); | ||
| } | ||
| } | ||
| }, | ||
| ExprKind::Let(let_expr) => { | ||
| collect_binding_from_let(cx, let_expr, &mut bindings); | ||
| }, | ||
| _ => {}, | ||
| } | ||
| ControlFlow::<()>::Continue(()) | ||
| }); | ||
|
|
||
| #[allow(rustc::potential_query_instability)] | ||
| let mut binding_vec: Vec<_> = bindings.into_iter().collect(); | ||
| binding_vec.sort_by_key(|(_, info)| info.ty_span.lo()); | ||
|
|
||
| for (hir_id, binding_info) in binding_vec { | ||
| check_binding_usages(cx, body, hir_id, &binding_info); | ||
| } | ||
| } | ||
|
|
||
| fn collect_binding_from_let<'a>( | ||
| cx: &LateContext<'a>, | ||
| let_expr: &rustc_hir::LetExpr<'a>, | ||
| bindings: &mut FxHashMap<HirId, BindingInfo<'a>>, | ||
| ) { | ||
| if let_expr.ty.is_none() | ||
| || let_expr.span.from_expansion() | ||
| || has_generic_return_type(cx, let_expr.init) | ||
| || contains_unsafe(let_expr.init) | ||
| { | ||
| return; | ||
| } | ||
|
|
||
| if let PatKind::Binding(_, hir_id, _, _) = let_expr.pat.kind | ||
| && let Some(ty_hir) = let_expr.ty | ||
| { | ||
| let ty = cx.typeck_results().pat_ty(let_expr.pat); | ||
| if ty.is_numeric() { | ||
| bindings.insert( | ||
| hir_id, | ||
| BindingInfo { | ||
| source_ty: ty, | ||
| ty_span: ty_hir.span, | ||
| }, | ||
| ); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn collect_binding_from_local<'a>( | ||
| cx: &LateContext<'a>, | ||
| let_stmt: &LetStmt<'a>, | ||
| bindings: &mut FxHashMap<HirId, BindingInfo<'a>>, | ||
| ) { | ||
| if let_stmt.ty.is_none() | ||
| || let_stmt.span.from_expansion() | ||
| || let_stmt | ||
| .init | ||
| .is_some_and(|init| has_generic_return_type(cx, init) || contains_unsafe(init)) | ||
| { | ||
| return; | ||
| } | ||
|
|
||
| if let PatKind::Binding(_, hir_id, _, _) = let_stmt.pat.kind | ||
| && let Some(ty_hir) = let_stmt.ty | ||
| { | ||
| let ty = cx.typeck_results().pat_ty(let_stmt.pat); | ||
| if ty.is_numeric() { | ||
| bindings.insert( | ||
| hir_id, | ||
| BindingInfo { | ||
| source_ty: ty, | ||
| ty_span: ty_hir.span, | ||
| }, | ||
| ); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn contains_unsafe(expr: &Expr<'_>) -> bool { | ||
| for_each_expr_without_closures(expr, |e| { | ||
| if let ExprKind::Block(block, _) = e.kind | ||
| && let BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided) = block.rules | ||
| { | ||
| return ControlFlow::Break(()); | ||
| } | ||
| ControlFlow::Continue(()) | ||
| }) | ||
| .is_some() | ||
| } | ||
|
|
||
| fn has_generic_return_type(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { | ||
| match &expr.kind { | ||
| ExprKind::Block(block, _) => { | ||
| if let Some(tail_expr) = block.expr { | ||
| return has_generic_return_type(cx, tail_expr); | ||
| } | ||
| false | ||
| }, | ||
| ExprKind::If(_, then_block, else_expr) => { | ||
| has_generic_return_type(cx, then_block) || else_expr.is_some_and(|e| has_generic_return_type(cx, e)) | ||
| }, | ||
| ExprKind::Match(_, arms, _) => arms.iter().any(|arm| has_generic_return_type(cx, arm.body)), | ||
| ExprKind::Loop(block, label, ..) => for_each_expr_without_closures(*block, |e| { | ||
| match e.kind { | ||
| ExprKind::Loop(..) => { | ||
| // Unlabeled breaks inside nested loops target the inner loop, not ours | ||
| return ControlFlow::Continue(Descend::No); | ||
| }, | ||
| ExprKind::Break(dest, Some(break_expr)) => { | ||
| let targets_this_loop = | ||
| dest.label.is_none() || dest.label.map(|l| l.ident) == label.map(|l| l.ident); | ||
| if targets_this_loop && has_generic_return_type(cx, break_expr) { | ||
| return ControlFlow::Break(()); | ||
| } | ||
| }, | ||
| _ => {}, | ||
| } | ||
| ControlFlow::Continue(Descend::Yes) | ||
| }) | ||
| .is_some(), | ||
| ExprKind::MethodCall(..) => { | ||
| if let Some(def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id) { | ||
| let sig = cx.tcx.fn_sig(def_id).instantiate_identity(); | ||
| let ret_ty = sig.output().skip_binder(); | ||
| return ret_ty.has_param(); | ||
| } | ||
| false | ||
| }, | ||
| ExprKind::Call(callee, _) => { | ||
| if let ExprKind::Path(qpath) = &callee.kind { | ||
| let res = cx.qpath_res(qpath, callee.hir_id); | ||
| if let Res::Def(DefKind::Fn | DefKind::AssocFn, def_id) = res { | ||
| let sig = cx.tcx.fn_sig(def_id).instantiate_identity(); | ||
| let ret_ty = sig.output().skip_binder(); | ||
| return ret_ty.has_param(); | ||
| } | ||
| } | ||
| false | ||
| }, | ||
| _ => false, | ||
| } | ||
| } | ||
|
|
||
| fn is_generic_res(cx: &LateContext<'_>, res: Res) -> bool { | ||
| let has_type_params = |def_id| { | ||
| cx.tcx | ||
| .generics_of(def_id) | ||
| .own_params | ||
| .iter() | ||
| .any(|p| p.kind.is_ty_or_const()) | ||
| }; | ||
| match res { | ||
| Res::Def(DefKind::Fn | DefKind::AssocFn, def_id) => has_type_params(def_id), | ||
| // Ctor → Variant → ADT: constructor's parent is variant, variant's parent is the ADT | ||
| Res::Def(DefKind::Ctor(..), def_id) => has_type_params(cx.tcx.parent(cx.tcx.parent(def_id))), | ||
| _ => false, | ||
| } | ||
| } | ||
|
|
||
| fn is_cast_in_generic_context<'a>(cx: &LateContext<'a>, cast_expr: &Expr<'a>) -> bool { | ||
| let mut current_id = cast_expr.hir_id; | ||
|
|
||
| loop { | ||
| let parent_id = cx.tcx.parent_hir_id(current_id); | ||
| if parent_id == current_id { | ||
| return false; | ||
| } | ||
|
|
||
| let parent = cx.tcx.hir_node(parent_id); | ||
|
|
||
| match parent { | ||
| rustc_hir::Node::Expr(parent_expr) => { | ||
| match &parent_expr.kind { | ||
| ExprKind::Closure(_) => return false, | ||
| ExprKind::Call(callee, _) => { | ||
| if let ExprKind::Path(qpath) = &callee.kind { | ||
| let res = cx.qpath_res(qpath, callee.hir_id); | ||
| if is_generic_res(cx, res) { | ||
| return true; | ||
| } | ||
| } | ||
| }, | ||
| ExprKind::MethodCall(..) => { | ||
| if let Some(def_id) = cx.typeck_results().type_dependent_def_id(parent_expr.hir_id) | ||
| && cx | ||
| .tcx | ||
| .generics_of(def_id) | ||
| .own_params | ||
| .iter() | ||
| .any(|p| p.kind.is_ty_or_const()) | ||
| { | ||
| return true; | ||
| } | ||
| }, | ||
| _ => {}, | ||
| } | ||
| current_id = parent_id; | ||
| }, | ||
| _ => return false, | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn check_binding_usages<'a>(cx: &LateContext<'a>, body: &Body<'a>, hir_id: HirId, binding_info: &BindingInfo<'a>) { | ||
| let mut usages = Vec::new(); | ||
|
|
||
| for_each_expr(cx, body.value, |expr| { | ||
| if let ExprKind::Path(ref qpath) = expr.kind | ||
| && !expr.span.from_expansion() | ||
| && let Res::Local(id) = cx.qpath_res(qpath, expr.hir_id) | ||
| && id == hir_id | ||
| { | ||
| let parent_id = cx.tcx.parent_hir_id(expr.hir_id); | ||
| let parent = cx.tcx.hir_node(parent_id); | ||
|
|
||
| let usage = if let rustc_hir::Node::Expr(parent_expr) = parent | ||
| && let ExprKind::Cast(..) = parent_expr.kind | ||
| && !parent_expr.span.from_expansion() | ||
| { | ||
| UsageInfo { | ||
| cast_to: Some(cx.typeck_results().expr_ty(parent_expr)), | ||
| in_generic_context: is_cast_in_generic_context(cx, parent_expr), | ||
| } | ||
| } else { | ||
| UsageInfo { | ||
| cast_to: None, | ||
| in_generic_context: false, | ||
| } | ||
| }; | ||
| usages.push(usage); | ||
| } | ||
| ControlFlow::<()>::Continue(()) | ||
| }); | ||
|
|
||
| let Some(first_target) = usages | ||
| .first() | ||
| .and_then(|u| u.cast_to) | ||
| .filter(|&t| t != binding_info.source_ty) | ||
| .filter(|&t| usages.iter().all(|u| u.cast_to == Some(t) && !u.in_generic_context)) | ||
| else { | ||
| return; | ||
| }; | ||
|
|
||
| span_lint_and_sugg( | ||
| cx, | ||
| NEEDLESS_TYPE_CAST, | ||
| binding_info.ty_span, | ||
| format!( | ||
| "this binding is defined as `{}` but is always cast to `{}`", | ||
| binding_info.source_ty, first_target | ||
| ), | ||
| "consider defining it as", | ||
| first_target.to_string(), | ||
| Applicability::MaybeIncorrect, | ||
| ); | ||
| } |
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whoa!