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Split out match_same_arms

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This commit is contained in:
Jason Newcomb 2022-02-06 13:53:51 -05:00
parent e41a6fc042
commit 64548250e7
2 changed files with 119 additions and 113 deletions
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112
clippy_lints/src/matches/match_same_arms.rs Normal file
View File

@ -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<HirId> = 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, "<pat1>");
let rhs = snippet(cx, j.pat.span, "<pat2>");
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()
}

120
clippy_lints/src/matches/mod.rs
View File

@ -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<HirId> = 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, "<pat1>");
let rhs = snippet(cx, j.pat.span, "<pat2>");
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()
}