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Merged
merged 3 commits into from
Feb 21, 2021
Merged

Teach SpanlessEq binding IDs #6754

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4ac14f9
Teach SpanlessEq binding IDs
camsteffen Feb 17, 2021
742922a
Make expr_fallback FnMut
camsteffen Feb 17, 2021
9ad6e26
Fix match_same_arms with SpanlessEq changes
camsteffen Feb 17, 2021
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113 changes: 50 additions & 63 deletions clippy_lints/src/matches.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,19 +3,19 @@ use crate::utils::sugg::Sugg;
use crate::utils::visitors::LocalUsedVisitor;
use crate::utils::{
expr_block, get_parent_expr, implements_trait, in_macro, indent_of, is_allowed, is_expn_of, is_refutable,
is_type_diagnostic_item, is_wild, match_qpath, match_type, meets_msrv, multispan_sugg, path_to_local_id,
peel_hir_pat_refs, peel_mid_ty_refs, peel_n_hir_expr_refs, remove_blocks, snippet, snippet_block, snippet_opt,
snippet_with_applicability, span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then,
strip_pat_refs,
is_type_diagnostic_item, is_wild, match_qpath, match_type, meets_msrv, multispan_sugg, path_to_local,
path_to_local_id, peel_hir_pat_refs, peel_mid_ty_refs, peel_n_hir_expr_refs, remove_blocks, snippet, snippet_block,
snippet_opt, snippet_with_applicability, span_lint_and_help, span_lint_and_note, span_lint_and_sugg,
span_lint_and_then, strip_pat_refs,
};
use crate::utils::{paths, search_same, SpanlessEq, SpanlessHash};
use if_chain::if_chain;
use rustc_ast::ast::LitKind;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_errors::Applicability;
use rustc_hir::def::CtorKind;
use rustc_hir::{
Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Guard, Local, MatchSource, Mutability, Node, Pat,
Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Guard, HirId, Local, MatchSource, Mutability, Node, Pat,
PatKind, QPath, RangeEnd,
};
use rustc_lint::{LateContext, LateLintPass, LintContext};
Expand All @@ -24,7 +24,7 @@ use rustc_middle::ty::{self, Ty, TyS};
use rustc_semver::RustcVersion;
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::source_map::{Span, Spanned};
use rustc_span::{sym, Symbol};
use rustc_span::sym;
use std::cmp::Ordering;
use std::collections::hash_map::Entry;
use std::collections::Bound;
Expand Down Expand Up @@ -1873,13 +1873,6 @@ fn test_overlapping() {

/// Implementation of `MATCH_SAME_ARMS`.
fn lint_match_arms<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) {
fn same_bindings<'tcx>(lhs: &FxHashMap<Symbol, Ty<'tcx>>, rhs: &FxHashMap<Symbol, Ty<'tcx>>) -> bool {
lhs.len() == rhs.len()
&& lhs
.iter()
.all(|(name, l_ty)| rhs.get(name).map_or(false, |r_ty| TyS::same_type(l_ty, r_ty)))
}

if let ExprKind::Match(_, ref arms, MatchSource::Normal) = expr.kind {
let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 {
let mut h = SpanlessHash::new(cx);
Expand All @@ -1891,12 +1884,38 @@ fn lint_match_arms<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) {
let min_index = usize::min(lindex, rindex);
let max_index = usize::max(lindex, rindex);

let mut local_map: FxHashMap<HirId, HirId> = FxHashMap::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).eq_expr(&lhs.body, &rhs.body) &&
// all patterns should have the same bindings
same_bindings(&bindings(cx, &lhs.pat), &bindings(cx, &rhs.pat))
(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();
Expand Down Expand Up @@ -1939,50 +1958,18 @@ fn lint_match_arms<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) {
}
}

/// Returns the list of bindings in a pattern.
fn bindings<'tcx>(cx: &LateContext<'tcx>, pat: &Pat<'_>) -> FxHashMap<Symbol, Ty<'tcx>> {
fn bindings_impl<'tcx>(cx: &LateContext<'tcx>, pat: &Pat<'_>, map: &mut FxHashMap<Symbol, Ty<'tcx>>) {
match pat.kind {
PatKind::Box(ref pat) | PatKind::Ref(ref pat, _) => bindings_impl(cx, pat, map),
PatKind::TupleStruct(_, pats, _) => {
for pat in pats {
bindings_impl(cx, pat, map);
}
},
PatKind::Binding(.., ident, ref as_pat) => {
if let Entry::Vacant(v) = map.entry(ident.name) {
v.insert(cx.typeck_results().pat_ty(pat));
}
if let Some(ref as_pat) = *as_pat {
bindings_impl(cx, as_pat, map);
}
},
PatKind::Or(fields) | PatKind::Tuple(fields, _) => {
for pat in fields {
bindings_impl(cx, pat, map);
}
},
PatKind::Struct(_, fields, _) => {
for pat in fields {
bindings_impl(cx, &pat.pat, map);
}
},
PatKind::Slice(lhs, ref mid, rhs) => {
for pat in lhs {
bindings_impl(cx, pat, map);
}
if let Some(ref mid) = *mid {
bindings_impl(cx, mid, map);
}
for pat in rhs {
bindings_impl(cx, pat, map);
}
},
PatKind::Lit(..) | PatKind::Range(..) | PatKind::Wild | PatKind::Path(..) => (),
}
}

let mut result = FxHashMap::default();
bindings_impl(cx, pat, &mut result);
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: FxHashSet<HirId>) -> bool {
let mut result = true;
pat.each_binding_or_first(&mut |_, id, _, _| result &= ids.remove(&id));
result && ids.is_empty()
}
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