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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
commit | 698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch) | |
tree | 173a775858bd501c378080a10dca74132f05bc50 /src/tools/clippy/clippy_lints/src/matches/needless_match.rs | |
parent | Initial commit. (diff) | |
download | rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip |
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/tools/clippy/clippy_lints/src/matches/needless_match.rs')
-rw-r--r-- | src/tools/clippy/clippy_lints/src/matches/needless_match.rs | 207 |
1 files changed, 207 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/matches/needless_match.rs b/src/tools/clippy/clippy_lints/src/matches/needless_match.rs new file mode 100644 index 000000000..fa19cddd3 --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/matches/needless_match.rs @@ -0,0 +1,207 @@ +use super::NEEDLESS_MATCH; +use clippy_utils::diagnostics::span_lint_and_sugg; +use clippy_utils::source::snippet_with_applicability; +use clippy_utils::ty::{is_type_diagnostic_item, same_type_and_consts}; +use clippy_utils::{ + eq_expr_value, get_parent_expr_for_hir, get_parent_node, higher, is_else_clause, is_lang_ctor, over, + peel_blocks_with_stmt, +}; +use rustc_errors::Applicability; +use rustc_hir::LangItem::OptionNone; +use rustc_hir::{Arm, BindingAnnotation, Expr, ExprKind, FnRetTy, Node, Pat, PatKind, Path, QPath}; +use rustc_lint::LateContext; +use rustc_span::sym; +use rustc_typeck::hir_ty_to_ty; + +pub(crate) fn check_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) { + if arms.len() > 1 && expr_ty_matches_p_ty(cx, ex, expr) && check_all_arms(cx, ex, arms) { + let mut applicability = Applicability::MachineApplicable; + span_lint_and_sugg( + cx, + NEEDLESS_MATCH, + expr.span, + "this match expression is unnecessary", + "replace it with", + snippet_with_applicability(cx, ex.span, "..", &mut applicability).to_string(), + applicability, + ); + } +} + +/// Check for nop `if let` expression that assembled as unnecessary match +/// +/// ```rust,ignore +/// if let Some(a) = option { +/// Some(a) +/// } else { +/// None +/// } +/// ``` +/// OR +/// ```rust,ignore +/// if let SomeEnum::A = some_enum { +/// SomeEnum::A +/// } else if let SomeEnum::B = some_enum { +/// SomeEnum::B +/// } else { +/// some_enum +/// } +/// ``` +pub(crate) fn check_if_let<'tcx>(cx: &LateContext<'tcx>, ex: &Expr<'_>, if_let: &higher::IfLet<'tcx>) { + if !is_else_clause(cx.tcx, ex) && expr_ty_matches_p_ty(cx, if_let.let_expr, ex) && check_if_let_inner(cx, if_let) { + let mut applicability = Applicability::MachineApplicable; + span_lint_and_sugg( + cx, + NEEDLESS_MATCH, + ex.span, + "this if-let expression is unnecessary", + "replace it with", + snippet_with_applicability(cx, if_let.let_expr.span, "..", &mut applicability).to_string(), + applicability, + ); + } +} + +fn check_all_arms(cx: &LateContext<'_>, match_expr: &Expr<'_>, arms: &[Arm<'_>]) -> bool { + for arm in arms { + let arm_expr = peel_blocks_with_stmt(arm.body); + if let PatKind::Wild = arm.pat.kind { + return eq_expr_value(cx, match_expr, strip_return(arm_expr)); + } else if !pat_same_as_expr(arm.pat, arm_expr) { + return false; + } + } + + true +} + +fn check_if_let_inner(cx: &LateContext<'_>, if_let: &higher::IfLet<'_>) -> bool { + if let Some(if_else) = if_let.if_else { + if !pat_same_as_expr(if_let.let_pat, peel_blocks_with_stmt(if_let.if_then)) { + return false; + } + + // Recursively check for each `else if let` phrase, + if let Some(ref nested_if_let) = higher::IfLet::hir(cx, if_else) { + return check_if_let_inner(cx, nested_if_let); + } + + if matches!(if_else.kind, ExprKind::Block(..)) { + let else_expr = peel_blocks_with_stmt(if_else); + if matches!(else_expr.kind, ExprKind::Block(..)) { + return false; + } + let ret = strip_return(else_expr); + let let_expr_ty = cx.typeck_results().expr_ty(if_let.let_expr); + if is_type_diagnostic_item(cx, let_expr_ty, sym::Option) { + if let ExprKind::Path(ref qpath) = ret.kind { + return is_lang_ctor(cx, qpath, OptionNone) || eq_expr_value(cx, if_let.let_expr, ret); + } + return false; + } + return eq_expr_value(cx, if_let.let_expr, ret); + } + } + + false +} + +/// Strip `return` keyword if the expression type is `ExprKind::Ret`. +fn strip_return<'hir>(expr: &'hir Expr<'hir>) -> &'hir Expr<'hir> { + if let ExprKind::Ret(Some(ret)) = expr.kind { + ret + } else { + expr + } +} + +/// Manually check for coercion casting by checking if the type of the match operand or let expr +/// differs with the assigned local variable or the function return type. +fn expr_ty_matches_p_ty(cx: &LateContext<'_>, expr: &Expr<'_>, p_expr: &Expr<'_>) -> bool { + if let Some(p_node) = get_parent_node(cx.tcx, p_expr.hir_id) { + match p_node { + // Compare match_expr ty with local in `let local = match match_expr {..}` + Node::Local(local) => { + let results = cx.typeck_results(); + return same_type_and_consts(results.node_type(local.hir_id), results.expr_ty(expr)); + }, + // compare match_expr ty with RetTy in `fn foo() -> RetTy` + Node::Item(..) => { + if let Some(fn_decl) = p_node.fn_decl() { + if let FnRetTy::Return(ret_ty) = fn_decl.output { + return same_type_and_consts(hir_ty_to_ty(cx.tcx, ret_ty), cx.typeck_results().expr_ty(expr)); + } + } + }, + // check the parent expr for this whole block `{ match match_expr {..} }` + Node::Block(block) => { + if let Some(block_parent_expr) = get_parent_expr_for_hir(cx, block.hir_id) { + return expr_ty_matches_p_ty(cx, expr, block_parent_expr); + } + }, + // recursively call on `if xxx {..}` etc. + Node::Expr(p_expr) => { + return expr_ty_matches_p_ty(cx, expr, p_expr); + }, + _ => {}, + } + } + false +} + +fn pat_same_as_expr(pat: &Pat<'_>, expr: &Expr<'_>) -> bool { + let expr = strip_return(expr); + match (&pat.kind, &expr.kind) { + // Example: `Some(val) => Some(val)` + (PatKind::TupleStruct(QPath::Resolved(_, path), tuple_params, _), ExprKind::Call(call_expr, call_params)) => { + if let ExprKind::Path(QPath::Resolved(_, call_path)) = call_expr.kind { + return over(path.segments, call_path.segments, |pat_seg, call_seg| { + pat_seg.ident.name == call_seg.ident.name + }) && same_non_ref_symbols(tuple_params, call_params); + } + }, + // Example: `val => val` + ( + PatKind::Binding(annot, _, pat_ident, _), + ExprKind::Path(QPath::Resolved( + _, + Path { + segments: [first_seg, ..], + .. + }, + )), + ) => { + return !matches!(annot, BindingAnnotation::Ref | BindingAnnotation::RefMut) + && pat_ident.name == first_seg.ident.name; + }, + // Example: `Custom::TypeA => Custom::TypeB`, or `None => None` + (PatKind::Path(QPath::Resolved(_, p_path)), ExprKind::Path(QPath::Resolved(_, e_path))) => { + return over(p_path.segments, e_path.segments, |p_seg, e_seg| { + p_seg.ident.name == e_seg.ident.name + }); + }, + // Example: `5 => 5` + (PatKind::Lit(pat_lit_expr), ExprKind::Lit(expr_spanned)) => { + if let ExprKind::Lit(pat_spanned) = &pat_lit_expr.kind { + return pat_spanned.node == expr_spanned.node; + } + }, + _ => {}, + } + + false +} + +fn same_non_ref_symbols(pats: &[Pat<'_>], exprs: &[Expr<'_>]) -> bool { + if pats.len() != exprs.len() { + return false; + } + + for i in 0..pats.len() { + if !pat_same_as_expr(&pats[i], &exprs[i]) { + return false; + } + } + + true +} |