From 64548250e7c740d0376d638214df65fb2ace35f1 Mon Sep 17 00:00:00 2001 From: Jason Newcomb Date: Sun, 6 Feb 2022 13:53:51 -0500 Subject: [PATCH] Split out `match_same_arms` --- clippy_lints/src/matches/match_same_arms.rs | 112 ++++++++++++++++++ clippy_lints/src/matches/mod.rs | 120 ++------------------ 2 files changed, 119 insertions(+), 113 deletions(-) create mode 100644 clippy_lints/src/matches/match_same_arms.rs diff --git a/clippy_lints/src/matches/match_same_arms.rs b/clippy_lints/src/matches/match_same_arms.rs new file mode 100644 index 000000000..7efbd540f --- /dev/null +++ b/clippy_lints/src/matches/match_same_arms.rs @@ -0,0 +1,112 @@ +use clippy_utils::diagnostics::span_lint_and_then; +use clippy_utils::source::snippet; +use clippy_utils::{path_to_local, search_same, SpanlessEq, SpanlessHash}; +use rustc_hir::{Arm, Expr, ExprKind, HirId, HirIdMap, HirIdSet, MatchSource, Pat, PatKind}; +use rustc_lint::LateContext; +use rustc_middle::ty::TyS; +use std::collections::hash_map::Entry; + +use super::MATCH_SAME_ARMS; + +pub(crate) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) { + if let ExprKind::Match(_, arms, MatchSource::Normal) = expr.kind { + let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 { + let mut h = SpanlessHash::new(cx); + h.hash_expr(arm.body); + h.finish() + }; + + let eq = |&(lindex, lhs): &(usize, &Arm<'_>), &(rindex, rhs): &(usize, &Arm<'_>)| -> bool { + let min_index = usize::min(lindex, rindex); + let max_index = usize::max(lindex, rindex); + + let mut local_map: HirIdMap = HirIdMap::default(); + let eq_fallback = |a: &Expr<'_>, b: &Expr<'_>| { + if_chain! { + if let Some(a_id) = path_to_local(a); + if let Some(b_id) = path_to_local(b); + let entry = match local_map.entry(a_id) { + Entry::Vacant(entry) => entry, + // check if using the same bindings as before + Entry::Occupied(entry) => return *entry.get() == b_id, + }; + // the names technically don't have to match; this makes the lint more conservative + if cx.tcx.hir().name(a_id) == cx.tcx.hir().name(b_id); + if TyS::same_type(cx.typeck_results().expr_ty(a), cx.typeck_results().expr_ty(b)); + if pat_contains_local(lhs.pat, a_id); + if pat_contains_local(rhs.pat, b_id); + then { + entry.insert(b_id); + true + } else { + false + } + } + }; + // Arms with a guard are ignored, those can’t always be merged together + // This is also the case for arms in-between each there is an arm with a guard + (min_index..=max_index).all(|index| arms[index].guard.is_none()) + && SpanlessEq::new(cx) + .expr_fallback(eq_fallback) + .eq_expr(lhs.body, rhs.body) + // these checks could be removed to allow unused bindings + && bindings_eq(lhs.pat, local_map.keys().copied().collect()) + && bindings_eq(rhs.pat, local_map.values().copied().collect()) + }; + + let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect(); + for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) { + span_lint_and_then( + cx, + MATCH_SAME_ARMS, + j.body.span, + "this `match` has identical arm bodies", + |diag| { + diag.span_note(i.body.span, "same as this"); + + // Note: this does not use `span_suggestion` on purpose: + // there is no clean way + // to remove the other arm. Building a span and suggest to replace it to "" + // makes an even more confusing error message. Also in order not to make up a + // span for the whole pattern, the suggestion is only shown when there is only + // one pattern. The user should know about `|` if they are already using it… + + let lhs = snippet(cx, i.pat.span, ""); + let rhs = snippet(cx, j.pat.span, ""); + + if let PatKind::Wild = j.pat.kind { + // if the last arm is _, then i could be integrated into _ + // note that i.pat cannot be _, because that would mean that we're + // hiding all the subsequent arms, and rust won't compile + diag.span_note( + i.body.span, + &format!( + "`{}` has the same arm body as the `_` wildcard, consider removing it", + lhs + ), + ); + } else { + diag.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs,)) + .help("...or consider changing the match arm bodies"); + } + }, + ); + } + } +} + +fn pat_contains_local(pat: &Pat<'_>, id: HirId) -> bool { + let mut result = false; + pat.walk_short(|p| { + result |= matches!(p.kind, PatKind::Binding(_, binding_id, ..) if binding_id == id); + !result + }); + result +} + +/// Returns true if all the bindings in the `Pat` are in `ids` and vice versa +fn bindings_eq(pat: &Pat<'_>, mut ids: HirIdSet) -> bool { + let mut result = true; + pat.each_binding_or_first(&mut |_, id, _, _| result &= ids.remove(&id)); + result && ids.is_empty() +} diff --git a/clippy_lints/src/matches/mod.rs b/clippy_lints/src/matches/mod.rs index ff07fc6d4..529f759ba 100644 --- a/clippy_lints/src/matches/mod.rs +++ b/clippy_lints/src/matches/mod.rs @@ -3,6 +3,7 @@ use clippy_utils::diagnostics::{ multispan_sugg, span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then, }; use clippy_utils::macros::{is_panic, root_macro_call}; +use clippy_utils::paths; use clippy_utils::peel_blocks_with_stmt; use clippy_utils::source::{expr_block, indent_of, snippet, snippet_block, snippet_opt, snippet_with_applicability}; use clippy_utils::sugg::Sugg; @@ -10,10 +11,8 @@ use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, match_type, pe use clippy_utils::visitors::is_local_used; use clippy_utils::{ get_parent_expr, is_lang_ctor, is_lint_allowed, is_refutable, is_unit_expr, is_wild, meets_msrv, msrvs, - path_to_local, path_to_local_id, peel_blocks, peel_hir_pat_refs, peel_n_hir_expr_refs, recurse_or_patterns, - strip_pat_refs, + path_to_local_id, peel_blocks, peel_hir_pat_refs, peel_n_hir_expr_refs, recurse_or_patterns, strip_pat_refs, }; -use clippy_utils::{paths, search_same, SpanlessEq, SpanlessHash}; use core::iter::once; use if_chain::if_chain; use rustc_ast::ast::LitKind; @@ -21,19 +20,18 @@ use rustc_errors::Applicability; use rustc_hir::def::{CtorKind, DefKind, Res}; use rustc_hir::LangItem::{OptionNone, OptionSome}; use rustc_hir::{ - self as hir, Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, HirId, Local, MatchSource, Mutability, - Node, Pat, PatKind, PathSegment, QPath, RangeEnd, TyKind, + self as hir, Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Local, MatchSource, Mutability, Node, Pat, + PatKind, PathSegment, QPath, RangeEnd, TyKind, }; -use rustc_hir::{HirIdMap, HirIdSet}; use rustc_lint::{LateContext, LateLintPass}; use rustc_middle::ty::{self, Ty, TyS, VariantDef}; use rustc_semver::RustcVersion; use rustc_session::{declare_tool_lint, impl_lint_pass}; use rustc_span::{sym, symbol::kw, Span}; use std::cmp::{max, Ordering}; -use std::collections::hash_map::Entry; mod match_like_matches; +mod match_same_arms; declare_clippy_lint! { /// ### What it does @@ -624,10 +622,10 @@ impl<'tcx> LateLintPass<'tcx> for Matches { if meets_msrv(self.msrv.as_ref(), &msrvs::MATCHES_MACRO) { if !match_like_matches::check(cx, expr) { - lint_match_arms(cx, expr); + match_same_arms::check(cx, expr); } } else { - lint_match_arms(cx, expr); + match_same_arms::check(cx, expr); } if let ExprKind::Match(ex, arms, MatchSource::Normal) = expr.kind { @@ -2185,107 +2183,3 @@ fn test_overlapping() { ],) ); } - -/// Implementation of `MATCH_SAME_ARMS`. -fn lint_match_arms<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) { - if let ExprKind::Match(_, arms, MatchSource::Normal) = expr.kind { - let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 { - let mut h = SpanlessHash::new(cx); - h.hash_expr(arm.body); - h.finish() - }; - - let eq = |&(lindex, lhs): &(usize, &Arm<'_>), &(rindex, rhs): &(usize, &Arm<'_>)| -> bool { - let min_index = usize::min(lindex, rindex); - let max_index = usize::max(lindex, rindex); - - let mut local_map: HirIdMap = HirIdMap::default(); - let eq_fallback = |a: &Expr<'_>, b: &Expr<'_>| { - if_chain! { - if let Some(a_id) = path_to_local(a); - if let Some(b_id) = path_to_local(b); - let entry = match local_map.entry(a_id) { - Entry::Vacant(entry) => entry, - // check if using the same bindings as before - Entry::Occupied(entry) => return *entry.get() == b_id, - }; - // the names technically don't have to match; this makes the lint more conservative - if cx.tcx.hir().name(a_id) == cx.tcx.hir().name(b_id); - if TyS::same_type(cx.typeck_results().expr_ty(a), cx.typeck_results().expr_ty(b)); - if pat_contains_local(lhs.pat, a_id); - if pat_contains_local(rhs.pat, b_id); - then { - entry.insert(b_id); - true - } else { - false - } - } - }; - // Arms with a guard are ignored, those can’t always be merged together - // This is also the case for arms in-between each there is an arm with a guard - (min_index..=max_index).all(|index| arms[index].guard.is_none()) - && SpanlessEq::new(cx) - .expr_fallback(eq_fallback) - .eq_expr(lhs.body, rhs.body) - // these checks could be removed to allow unused bindings - && bindings_eq(lhs.pat, local_map.keys().copied().collect()) - && bindings_eq(rhs.pat, local_map.values().copied().collect()) - }; - - let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect(); - for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) { - span_lint_and_then( - cx, - MATCH_SAME_ARMS, - j.body.span, - "this `match` has identical arm bodies", - |diag| { - diag.span_note(i.body.span, "same as this"); - - // Note: this does not use `span_suggestion` on purpose: - // there is no clean way - // to remove the other arm. Building a span and suggest to replace it to "" - // makes an even more confusing error message. Also in order not to make up a - // span for the whole pattern, the suggestion is only shown when there is only - // one pattern. The user should know about `|` if they are already using it… - - let lhs = snippet(cx, i.pat.span, ""); - let rhs = snippet(cx, j.pat.span, ""); - - if let PatKind::Wild = j.pat.kind { - // if the last arm is _, then i could be integrated into _ - // note that i.pat cannot be _, because that would mean that we're - // hiding all the subsequent arms, and rust won't compile - diag.span_note( - i.body.span, - &format!( - "`{}` has the same arm body as the `_` wildcard, consider removing it", - lhs - ), - ); - } else { - diag.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs,)) - .help("...or consider changing the match arm bodies"); - } - }, - ); - } - } -} - -fn pat_contains_local(pat: &Pat<'_>, id: HirId) -> bool { - let mut result = false; - pat.walk_short(|p| { - result |= matches!(p.kind, PatKind::Binding(_, binding_id, ..) if binding_id == id); - !result - }); - result -} - -/// Returns true if all the bindings in the `Pat` are in `ids` and vice versa -fn bindings_eq(pat: &Pat<'_>, mut ids: HirIdSet) -> bool { - let mut result = true; - pat.each_binding_or_first(&mut |_, id, _, _| result &= ids.remove(&id)); - result && ids.is_empty() -}